Smartphone-Based Food Diagnostic Technologies: A Review
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paper_title: Mobile phones democratize and cultivate next-generation imaging, diagnostics and measurement tools

paper_content:

In this article, I discuss some of the emerging applications and the future opportunities and challenges created by the use of mobile phones and their embedded components for the development of next-generation imaging, sensing, diagnostics and measurement tools. The massive volume of mobile phone users, which has now reached ~7 billion, drives the rapid improvements of the hardware, software and high-end imaging and sensing technologies embedded in our phones, transforming the mobile phone into a cost-effective and yet extremely powerful platform to run, e.g., biomedical tests, and perform scientific measurements that would normally require advanced laboratory instruments. This rapidly evolving and continuing trend will help us transform how medicine, engineering and sciences are practiced and taught globally.
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paper_title: Optical Imaging of Paramagnetic Bead-DNA Aggregation Inhibition Allows for Low Copy Number Detection of Infectious Pathogens

paper_content:

DNA-paramagnetic silica bead aggregation in a rotating magnetic field facilitates the quantification of DNA with femtogram sensitivity, but yields no sequence-specific information. Here we provide an original description of aggregation inhibition for the detection of DNA and RNA in a sequence-specific manner following loop-mediated isothermal amplification (LAMP). The fragments generated via LAMP fail to induce chaotrope-mediated bead aggregation; however, due to their ability to passivate the bead surface, they effectively inhibit bead aggregation by longer ‘trigger’ DNA. We demonstrate the utility of aggregation inhibition as a method for the detection of bacterial and viral pathogens with sensitivity that approaches single copies of the target. We successfully use this methodology for the detection of notable food-borne pathogens Escherichia coli O157:H7 and Salmonella enterica, as well as Rift Valley fever virus, a weaponizable virus of national security concern. We also show the concentration dependence of aggregation inhibition, suggesting the potential for quantification of target nucleic acid in clinical and environmental samples. Lastly, we demonstrate the ability to rapidly detect infectious pathogens by utilizing a cell phone and custom-written application (App), making this novel detection modality fully portable for point-of-care use.
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paper_title: Programmable living material containing reporter micro-organisms permits quantitative detection of oligosaccharides.

paper_content:

The increasing molecular understanding of many diseases today permits the development of new diagnostic methods. However, few easy-to-handle and inexpensive tools exist for common diseases such as food disorders. Here we present a living material based analytical sensor (LiMBAS) containing genetically modified bacteria (Escherichia coli) immobilized and protected in a thin layer between a nanoporous and support polymer membrane for a facile quantification of disease-relevant oligosaccharides. The bacteria were engineered to fluoresce in response to the analyte to reveal its diffusion behavior when using a blue-light source and optical filter. We demonstrated that the diffusion zone diameter was related semi-logarithmically to the analyte concentration. LiMBAS could accurately quantify lactose or galactose in undiluted food samples and was able to measure food intolerance relevant concentrations in the range of 1-1000 mM requiring a sample volume of 1-10 μL. LiMBAS was storable for at least seven days without losing functionality at 4 °C. A wide range of genetic tools for E. coli are readily available thus allowing the reprogramming of the material to serve as biosensor for other molecules. In combination with smartphones, an automated diagnostic analysis becomes feasible which would also allow untrained people to use LiMBAS.
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paper_title: Portable detection of clenbuterol using a smartphone-based electrochemical biosensor with electric field-driven acceleration

paper_content:

Abstract We have developed a fast, highly sensitive and low-cost biosensing system for the detection of clenbuterol (CLB), using a homemade mobile electrochemical device with an electric field-driven acceleration strategy. This system consists of an embedded circuit in smartphone for signal processing and a screen-printed carbon electrode (SPCE) modified with multi-walled carbon nanotubes (MWNTs) and goat anti mouse-immunoglobulin G (IgG) sensing layer (MWNTs-I-layer). CLB monoclonal antibody was assembled through its binding to the surface-confined antibody. Such modified electrodes were used for rapid and sensitive amperometric immunosensing detection of CLB. Horseradish peroxidase-coupled CLB (CLB–HRP) competed with free CLB in the samples to bind the monoclonal antibody. By using this mobile system, we could detect CLB ranging from 0.3 ng ⋅ mL − 1 to 100 ng ⋅ mL − 1 with the detection limit of 0.076 ng ⋅ mL − 1 . The whole competitive-type detection process was finished within 6 min. We expect this device can meet the requirements for field detection of various food security-related species.
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paper_title: Disposable lateral flow-through strip for smartphone-camera to quantitatively detect alkaline phosphatase activity in milk.

paper_content:

A disposable lateral flow-through strip was developed for smartphone to fast one-step quantitatively detect alkaline phosphatase (ALP) activity in raw milk. The strip comprises two functional components, a conjugation pad loaded with phosphotyrosine-coated gold nanoparticles (AuNPs@Cys-Try-p) and a testing line coated with anti-phosphotryosine antibody (anti-Tyr-p mAb). The dephosphorylation activity of ALP at the testing zone can be quantitatively assayed by monitoring the accumulated AuNPs-induced color changes by smartphone camera, thus providing a highly convenient portable detection method. A trace amount of ALP as low as 0.1UL(-1) with a linear dynamic range of 0.1-150UL(-1) (R(2)=0.999) in pasteurized milk and raw milk can be one-step detected by the developed flow-through strip within 10min, demonstrating the potential of smartphone-based portable sensing device for pathogen detection. This bio-hazards free lateral flow-through testing strip can be also used to fabricate rapid, sensitive and inexpensive enzyme or immunosensors for broad portable clinic diagnosis and food contamination analysis, particularly in point-of-care and daily food quality inspection.
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paper_title: Smartphone-interfaced lab-on-a-chip devices for field-deployable enzyme-linked immunosorbent assay

paper_content:

The emerging technologies on mobile-based diagnosis and bioanalytical detection have enabled powerful laboratory assays such as enzyme-linked immunosorbent assay (ELISA) to be conducted in field-use lab-on-a-chip devices. In this paper, we present a low-cost universal serial bus (USB)-interfaced mobile platform to perform microfluidic ELISA operations in detecting the presence and concentrations of BDE-47 (2,2′,4,4′-tetrabromodiphenyl ether), an environmental contaminant found in our food supply with adverse health impact. Our point-of-care diagnostic device utilizes flexible interdigitated carbon black electrodes to convert electric current into a microfluidic pump via gas bubble expansion during electrolytic reaction. The micropump receives power from a mobile phone and transports BDE-47 analytes through the microfluidic device conducting competitive ELISA. Using variable domain of heavy chain antibodies (commonly referred to as single domain antibodies or Nanobodies), the proposed device is sensitive for a BDE-47 concentration range of 10−3–104 μg/l, with a comparable performance to that uses a standard competitive ELISA protocol. It is anticipated that the potential impact in mobile detection of health and environmental contaminants will prove beneficial to our community and low-resource environments.
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paper_title: An iPhone-based digital image colorimeter for detecting tetracycline in milk

paper_content:

Abstract An iPhone-based digital image colorimeter (DIC) was fabricated as a portable tool for monitoring tetracycline (TC) in bovine milk. An application named ColorConc was developed for the iPhone that utilizes an image matching algorithm to determine the TC concentration in a solution. The color values; red (R), green (G), blue (B), hue (H), saturation (S), brightness (V), and gray (Gr) were measured from each pictures of the TC standard solutions. TC solution extracted from milk samples using solid phase extraction (SPE) was captured and the concentration was predicted by comparing color values with those collected in a database. The amount of TC could be determined in the concentration range of 0.5–10 μg mL −1 . The proposed DIC-iPhone is able to provide a limit of detection (LOD) of 0.5 μg mL −1 and limit of quantitation (LOQ) of 1.5 μg mL −1 . The enrichment factor was 70 and color of the extracted milk sample was a strong yellow solution after SPE. Therefore, the SPE-DIC-iPhone could be used for the assay of TC residues in milk at the concentration lower than LOD and LOQ of the proposed technique.
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paper_title: Paper microfluidics for red wine tasting

paper_content:

A paper microfluidic chip was designed and fabricated to evaluate the taste of 10 different red wines using a set of chemical dyes. The digital camera of a smartphone captured the images, and its red-green-blue (RGB) pixel intensities were analyzed by principal component analysis (PCA). Using 8 dyes and 2 principal components (PCs), we were able to distinguish each wine by the grape variety and the oxidation status. Through comparing with the flavor map by human evaluation, PC1 seemed to represent the sweetness and PC2 the bodyness of red wine. This superior performance is attributed to: (1) careful selection of commercially available dyes through a series of linear correlation studies with the taste chemicals in red wines, (2) minimization of sample-to-sample variation by splitting a single sample into multiple wells on the paper microfluidics, and (3) filtration of particulate matter through paper fibers. The image processing and PCA procedure can eventually be implemented as a stand-alone smartphone application and can be adopted as an extremely low-cost, disposable, fully handheld, easy-to-use, yet sensitive and specific quality control method for appraising red wine or similar beverage products in resource-limited environments.
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paper_title: A personalized food allergen testing platform on a cellphone.

paper_content:

We demonstrate a personalized food allergen testing platform, termed iTube, running on a cellphone that images and automatically analyses colorimetric assays performed in test tubes toward sensitive and specific detection of allergens in food samples. This cost-effective and compact iTube attachment, weighing approximately 40 grams, is mechanically installed on the existing camera unit of a cellphone, where the test and control tubes are inserted from the side and are vertically illuminated by two separate light-emitting-diodes. The illumination light is absorbed by the allergen assay, which is activated within the tubes, causing an intensity change in the acquired images by the cellphone camera. These transmission images of the sample and control tubes are digitally processed within 1 s using a smart application running on the same cellphone for detection and quantification of allergen contamination in food products. We evaluated the performance of this cellphone-based iTube platform using different types of commercially available cookies, where the existence of peanuts was accurately quantified after a sample preparation and incubation time of ~20 min per test. This automated and cost-effective personalized food allergen testing tool running on cellphones can also permit uploading of test results to secure servers to create personal and/or public spatio-temporal allergen maps, which can be useful for public health in various settings.
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paper_title: Monitoring of fluoride in water samples using a smartphone.

paper_content:

In several parts of India, groundwater is the only reliable, year round source for drinking water. Prevention of fluorosis, a chronic disease resulting from excess intake of fluoride, requires the screening of all groundwater sources for fluoride in endemic areas. In this paper, the authors present a field deployable colorimetric analyzer based on an inexpensive smartphone embedded with digital camera for taking photograph of the colored solution as well as an easy-fit, and compact sample chamber (Akvo Caddisfly). Phones marketed by different smartphone makers were used. Commercially available zirconium xylenol orange reagent was used for determining fluoride concentration. A software program was developed to use with the phone for recording and analyzing the RGB color of the picture. Linear range for fluoride estimation was 0-2mgl(-1). Around 200 samples, which consisted of laboratory prepared as well as field samples collected from different locations in Karnataka, India, were tested with Akvo Caddisfly. The results showed a significant positive correlation between Ion Selective Electrode (ISE) method and Akvo Caddisfly (Phones A, B and C), with correlation coefficient ranging between 0.9952 and 1.000. In addition, there was no significant difference in the mean fluoride content values between ISE and Phone B and C except for Phone A. Thus the smartphone method is economical and suited for groundwater fluoride analysis in the field.
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paper_title: Use of plastic-based analytical device, smartphone and chemometric tools to discriminate amines

paper_content:

Amine-based volatile compounds released by microorganisms offer an alternative diagnostic approach for the identification of foodborne pathogens. Our objective has been to solvent cast cellulose acetate membranes to immobilise dyes and to use the resultant membranes as a plastic device to discriminate between different types of amines (triethylamine, isobutylamine, isopentylamine). The plastic device consisted of an array of membranes with five pH indicators (namely alizarin, bromophenol blue, chlorophenol red, methyl red and thymol blue). To analyse the data using a portable instrument, we used an iPhone® to obtain images and to extract red, green and blue colours (RGB) using in-house software before and after contact with each individual amine. All the RGB values extracted for each analyte allowed us to generate a unique colour pattern, which was used as input for non-supervised pattern recognition methods. Based on this analysis, it was possible to clearly discriminate between the amines studied without any misclassification, demonstrating that the device is well-suited for large-scale applications such as non-destructive methods to discriminate amines and, in future, for smart packaging applications in order to give early warning of rotting food that may lead to food poisoning. Additionally, a semi-quantitative analysis was performed and we have demonstrated that it is possible to quantify concentrations of amines down to 1 ppm.
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paper_title: A sensing smartphone and its portable accessory for on-site rapid biochemical detection of marine toxins

paper_content:

Okadaic acid (OA) and saxitoxin (STX) are common marine toxins which can accumulate in shellfish and affect human health through the food chain. A convenient and efficient method is urgently required to perform on-site detection of marine toxins to avoid frequent poisoning incidents. In this work, a smartphone-based system cooperating with competitive immunoassay strips was designed for rapid on-site detection of OA and STX. The smartphone was employed as a light detector for image acquisition and data processing. The 3D-printed portable accessory of the smartphone was utilized to fix the test strips. The homemade APP – iStrip used the pixel scan to obtain the valley value of the pixel curve as the output of the strip. The strip analytical method was easy to operate with a detection limit of 2.800 ng ml−1 for OA and 9.808 ng ml−1 for STX. Moreover, with the optimization of the antigen–antibody ratio on the strip, it provided quantitative analysis of OA and STX in the range of 3–20 ng ml−1 and 10–100 ng ml−1, respectively. Taking advantage of the smartphone and biochemical analysis, the strip analytical system will be a promising tool for on-site rapid detection of these two toxins.
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paper_title: Food contamination monitoring via internet of things, exemplified by using pocket-sized immunosensor as terminal unit

paper_content:

Abstract Healthcare via internet-of-things (IoT) for protection against consumption of contaminated foods was demonstrated via immuno-analysis of pathogenic bacteria and the sharing of results using a mobile device. As wireless internet has spread widely over the world, it can be readily used to communicate information related to, for example, human health. Indeed, some institutes have demonstrated the measurement of physical vital signals (e.g., temperature, pulse, and heartbeat) of the body for monitoring through a smartphone. However, biochemical analytes such as proteins and bacteria are currently difficult to measure based on antigen-antibody binding due to several technological barriers. Among them, the terminal unit of detection for, for instance, pathogens is mostly bulky, insensitive, or even expensive for sophisticated devices. We have studied the use of CMOS image sensor (CIS) for detecting the signal produced from an immuno-analytical system, which could resolve the detection issue hindering monitoring via IoT. In this study, an immunosensor system using CIS for detection means was fabricated to pocket-sized dimensions and then employed for determining a food-borne pathogen, the Vibrio species, in real samples. The analysis was controlled and monitored using a smartphone that was also used to upload the result as data to the internet server for sharing with the public. To our knowledge, this study could be the first exemplification of pathogen monitoring via IoT in the field of healthcare.
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paper_title: A simple paper-strip colorimetric method utilizing dehydrogenase enzymes for analysis of food components

paper_content:

In this study, we present a simple chromatographic paper-based colorimetric assay for the analysis of selected food compounds. The biochemical principle utilises enzymes from the dehydrogenase family coupled with diaphorase in the presence of a tetrazolium dye, MTT, and NAD+. The colored reaction product that developed on the surface of the chromatography paper could either be qualitatively analysed by the naked eye, that is, it could be used for screening analysis, or it could be recorded by using a smartphone camera and evaluated in freeware ImageJ in order to obtain data for quantitative analysis. The general concept was demonstrated and optimised using (L)-glutamate dehydrogenase and the versatility of the proposed method was illustrated by using other enzymes from the dehydrogenase family. The linear range for (L)-glutamate was found to be 0.5–5.0 mmol L−1 using the digital image method. The limit of detection found by the naked eye was 0.05 mmol L−1 and 0.028 mmol L−1 by digital imaging. The paper assay stored in a freezer provided a reproducible response for at least 6 weeks. This research presents the successful modification of an MTT-cell viability test principle and its use in the fabrication of an inexpensive, easy to prepare, simple to use, portable and rapid-responding paper-based assay.
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paper_title: Quantum dot enabled detection of Escherichia coli using a cell-phone

paper_content:

We report a cell-phone based Escherichia coli (E. coli) detection platform for screening of liquid samples. In this compact and cost-effective design attached to a cell-phone, we utilize anti-E. coli O157:H7 antibody functionalized glass capillaries as solid substrates to perform a quantum dot based sandwich assay for specific detection of E. coli O157:H7 in liquid samples. Using battery-powered inexpensive light-emitting-diodes (LEDs) we excite/pump these labelled E. coli particles captured on the capillary surface, where the emission from the quantum dots is then imaged using the cell-phone camera unit through an additional lens that is inserted between the capillary and the cell-phone. By quantifying the fluorescent light emission from each capillary tube, the concentration of E. coli in the sample is determined. We experimentally confirmed the detection limit of this cell-phone based fluorescent imaging and sensing platform as ∼5 to 10 cfu mL−1 in buffer solution. We also tested the specificity of this E. coli detection platform by spiking samples with different species (e.g., Salmonella) to confirm that non-specific binding/detection is negligible. We further demonstrated the proof-of-concept of our approach in a complex food matrix, e.g., fat-free milk, where a similar detection limit of ∼5 to 10 cfu mL−1 was achieved despite challenges associated with the density of proteins that exist in milk. Our results reveal the promising potential of this cell-phone enabled field-portable and cost-effective E. coli detection platform for e.g., screening of water and food samples even in resource limited environments. The presented platform can also be applicable to other pathogens of interest through the use of different antibodies.
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paper_title: Performance Improvement of the One-Dot Lateral Flow Immunoassay for Aflatoxin B1 by Using a Smartphone-Based Reading System

paper_content:

This study was conducted to develop a simple, rapid, and accurate lateral flow immunoassay (LFIA) detection method for point-of-care diagnosis. The one-dot LFIA for aflatoxin B1 (AFB1) was based on the modified competitive binding format using competition between AFB1 and colloidal gold-AFB1-BSA conjugate for antibody binding sites in the test zone. A Smartphone-based reading system consisting of a Samsung Galaxy S2 Smartphone, a LFIA reader, and a Smartphone application for the image acquisition and data analysis. The detection limit of one-dot LFIA for AFB1 is 5 μg/kg. This method provided semi-quantitative analysis of AFB1 samples in the range of 5 to 1,000 μg/kg. Using combination of the one-dot LFIA and the Smartphone-based reading system, it is possible to conduct a more fast and accurate point-of-care diagnosis.
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paper_title: Cellphone-based detection platform for rbST biomarker analysis in milk extracts using a microsphere fluorescence immunoassay

paper_content:

Current contaminant and residue monitoring throughout the food chain is based on sampling, transport, administration, and analysis in specialized control laboratories. This is a highly inefficient and costly process since typically more than 99% of the samples are found to be compliant. On-site simplified prescreening may provide a scenario in which only samples that are suspect are transported and further processed. Such a prescreening can be performed using a small attachment on a cellphone. To this end, a cellphone-based imaging platform for a microsphere fluorescence immunoassay that detects the presence of anti-recombinant bovine somatotropin (rbST) antibodies in milk extracts was developed. RbST administration to cows increases their milk production, but is illegal in the EU and a public health concern in the USA. The cellphone monitors the presence of anti-rbST antibodies (rbST biomarker), which are endogenously produced upon administration of rbST and excreted in milk. The rbST biomarker present in milk extracts was captured by rbST covalently coupled to paramagnetic microspheres and labeled by quantum dot (QD)-coupled detection antibodies. The emitted fluorescence light from these captured QDs was then imaged using the cellphone camera. Additionally, a dark-field image was taken in which all microspheres present were visible. The fluorescence and dark-field microimages were analyzed using a custom-developed Android application running on the same cellphone. With this setup, the microsphere fluorescence immunoassay and cellphone-based detection were successfully applied to milk sample extracts from rbST-treated and untreated cows. An 80% true-positive rate and 95% true-negative rate were achieved using this setup. Next, the cellphone-based detection platform was benchmarked against a newly developed planar imaging array alternative and found to be equally performing versus the much more sophisticated alternative. Using cellphone-based on-site analysis in future residue monitoring can limit the number of samples for laboratory analysis already at an early stage. Therewith, the entire monitoring process can become much more efficient and economical.
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paper_title: A smartphone-based colorimetric reader coupled with a remote server for rapid on-site catechols analysis

paper_content:

Abstract The search of a practical method to analyze cis-diol-containing compounds outside laboratory settings remains a substantial scientific challenge. Herein, a smartphone-based colorimetric reader was coupled with a remote server for rapid on-site analysis of catechols. A smallest-scale 2×2 colorimetric sensor array composed of pH indicators and phenylboronic acid was configured. The array was able to distinguish 13 catechols at 6 serial concentrations, through simultaneous treatment via principal component analysis, hierarchical cluster analysis, and linear discriminant analysis. After both the discriminatory power of the array and the prediction ability of the partial least squares quantitative models were proved to be predominant, the smartphone was coupled to the remote server. All the ΔRGB data were uploaded to the remote server wherein linear discriminant analysis and partial least squares processing modules were established to provide qualitative discrimination and quantitative calculation, respectively, of the analytes in real time. The applicability of this novel method to a real-life scenario was confirmed by the on-site analysis of various catechols from a water sample of the Yangtze River; the feedback result in the smartphone showed the method was able to identify the catechols with 100% accuracy and predict the concentrations to within 0.706–2.240 standard deviation.
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paper_title: Point-of-use electroanalytical platform based on homemade potentiostat and smartphone for multivariate data processing

paper_content:

Abstract We herein report a potential point-of-use platform for multivariate analyses by presenting homemade potentiostat and smartphone. This system combined high-performance detection (linear sweep, cyclic, and square wave voltammetry) with great simplicity, low-cost, portability, autonomy (6 h), and cable-free (wireless communication) device. In addition, the smartphone showed ability for processing complex and multivariate data. To the best of our knowledge, this paper is the first reporting about the development of a totally integrated point-of-use system with chemometric data processing on smartphone. This feature is essential for in-situ assays by allowing the real-time accomplishment of the entire analytical measurement at remote places. Such ability further reduces the occurrence of model overfitting by non-expert users. As proof-of-concept, our system was successfully applied to fingerprint Brazilian honey samples according to their botanical and geographic origins. The method relied on the unsupervised technique of principal component analysis (PCA) and the assays were performed by cyclic voltammetry using a single and non-modified working electrode of gold.
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paper_title: Programmable living material containing reporter micro-organisms permits quantitative detection of oligosaccharides.

paper_content:

The increasing molecular understanding of many diseases today permits the development of new diagnostic methods. However, few easy-to-handle and inexpensive tools exist for common diseases such as food disorders. Here we present a living material based analytical sensor (LiMBAS) containing genetically modified bacteria (Escherichia coli) immobilized and protected in a thin layer between a nanoporous and support polymer membrane for a facile quantification of disease-relevant oligosaccharides. The bacteria were engineered to fluoresce in response to the analyte to reveal its diffusion behavior when using a blue-light source and optical filter. We demonstrated that the diffusion zone diameter was related semi-logarithmically to the analyte concentration. LiMBAS could accurately quantify lactose or galactose in undiluted food samples and was able to measure food intolerance relevant concentrations in the range of 1-1000 mM requiring a sample volume of 1-10 μL. LiMBAS was storable for at least seven days without losing functionality at 4 °C. A wide range of genetic tools for E. coli are readily available thus allowing the reprogramming of the material to serve as biosensor for other molecules. In combination with smartphones, an automated diagnostic analysis becomes feasible which would also allow untrained people to use LiMBAS.
---
paper_title: A personalized food allergen testing platform on a cellphone.

paper_content:

We demonstrate a personalized food allergen testing platform, termed iTube, running on a cellphone that images and automatically analyses colorimetric assays performed in test tubes toward sensitive and specific detection of allergens in food samples. This cost-effective and compact iTube attachment, weighing approximately 40 grams, is mechanically installed on the existing camera unit of a cellphone, where the test and control tubes are inserted from the side and are vertically illuminated by two separate light-emitting-diodes. The illumination light is absorbed by the allergen assay, which is activated within the tubes, causing an intensity change in the acquired images by the cellphone camera. These transmission images of the sample and control tubes are digitally processed within 1 s using a smart application running on the same cellphone for detection and quantification of allergen contamination in food products. We evaluated the performance of this cellphone-based iTube platform using different types of commercially available cookies, where the existence of peanuts was accurately quantified after a sample preparation and incubation time of ~20 min per test. This automated and cost-effective personalized food allergen testing tool running on cellphones can also permit uploading of test results to secure servers to create personal and/or public spatio-temporal allergen maps, which can be useful for public health in various settings.
---
paper_title: Quantum dot enabled detection of Escherichia coli using a cell-phone

paper_content:

We report a cell-phone based Escherichia coli (E. coli) detection platform for screening of liquid samples. In this compact and cost-effective design attached to a cell-phone, we utilize anti-E. coli O157:H7 antibody functionalized glass capillaries as solid substrates to perform a quantum dot based sandwich assay for specific detection of E. coli O157:H7 in liquid samples. Using battery-powered inexpensive light-emitting-diodes (LEDs) we excite/pump these labelled E. coli particles captured on the capillary surface, where the emission from the quantum dots is then imaged using the cell-phone camera unit through an additional lens that is inserted between the capillary and the cell-phone. By quantifying the fluorescent light emission from each capillary tube, the concentration of E. coli in the sample is determined. We experimentally confirmed the detection limit of this cell-phone based fluorescent imaging and sensing platform as ∼5 to 10 cfu mL−1 in buffer solution. We also tested the specificity of this E. coli detection platform by spiking samples with different species (e.g., Salmonella) to confirm that non-specific binding/detection is negligible. We further demonstrated the proof-of-concept of our approach in a complex food matrix, e.g., fat-free milk, where a similar detection limit of ∼5 to 10 cfu mL−1 was achieved despite challenges associated with the density of proteins that exist in milk. Our results reveal the promising potential of this cell-phone enabled field-portable and cost-effective E. coli detection platform for e.g., screening of water and food samples even in resource limited environments. The presented platform can also be applicable to other pathogens of interest through the use of different antibodies.
---
paper_title: Cellphone-based detection platform for rbST biomarker analysis in milk extracts using a microsphere fluorescence immunoassay

paper_content:

Current contaminant and residue monitoring throughout the food chain is based on sampling, transport, administration, and analysis in specialized control laboratories. This is a highly inefficient and costly process since typically more than 99% of the samples are found to be compliant. On-site simplified prescreening may provide a scenario in which only samples that are suspect are transported and further processed. Such a prescreening can be performed using a small attachment on a cellphone. To this end, a cellphone-based imaging platform for a microsphere fluorescence immunoassay that detects the presence of anti-recombinant bovine somatotropin (rbST) antibodies in milk extracts was developed. RbST administration to cows increases their milk production, but is illegal in the EU and a public health concern in the USA. The cellphone monitors the presence of anti-rbST antibodies (rbST biomarker), which are endogenously produced upon administration of rbST and excreted in milk. The rbST biomarker present in milk extracts was captured by rbST covalently coupled to paramagnetic microspheres and labeled by quantum dot (QD)-coupled detection antibodies. The emitted fluorescence light from these captured QDs was then imaged using the cellphone camera. Additionally, a dark-field image was taken in which all microspheres present were visible. The fluorescence and dark-field microimages were analyzed using a custom-developed Android application running on the same cellphone. With this setup, the microsphere fluorescence immunoassay and cellphone-based detection were successfully applied to milk sample extracts from rbST-treated and untreated cows. An 80% true-positive rate and 95% true-negative rate were achieved using this setup. Next, the cellphone-based detection platform was benchmarked against a newly developed planar imaging array alternative and found to be equally performing versus the much more sophisticated alternative. Using cellphone-based on-site analysis in future residue monitoring can limit the number of samples for laboratory analysis already at an early stage. Therewith, the entire monitoring process can become much more efficient and economical.
---
paper_title: Programmable living material containing reporter micro-organisms permits quantitative detection of oligosaccharides.

paper_content:

The increasing molecular understanding of many diseases today permits the development of new diagnostic methods. However, few easy-to-handle and inexpensive tools exist for common diseases such as food disorders. Here we present a living material based analytical sensor (LiMBAS) containing genetically modified bacteria (Escherichia coli) immobilized and protected in a thin layer between a nanoporous and support polymer membrane for a facile quantification of disease-relevant oligosaccharides. The bacteria were engineered to fluoresce in response to the analyte to reveal its diffusion behavior when using a blue-light source and optical filter. We demonstrated that the diffusion zone diameter was related semi-logarithmically to the analyte concentration. LiMBAS could accurately quantify lactose or galactose in undiluted food samples and was able to measure food intolerance relevant concentrations in the range of 1-1000 mM requiring a sample volume of 1-10 μL. LiMBAS was storable for at least seven days without losing functionality at 4 °C. A wide range of genetic tools for E. coli are readily available thus allowing the reprogramming of the material to serve as biosensor for other molecules. In combination with smartphones, an automated diagnostic analysis becomes feasible which would also allow untrained people to use LiMBAS.
---
paper_title: Smartphone-interfaced lab-on-a-chip devices for field-deployable enzyme-linked immunosorbent assay

paper_content:

The emerging technologies on mobile-based diagnosis and bioanalytical detection have enabled powerful laboratory assays such as enzyme-linked immunosorbent assay (ELISA) to be conducted in field-use lab-on-a-chip devices. In this paper, we present a low-cost universal serial bus (USB)-interfaced mobile platform to perform microfluidic ELISA operations in detecting the presence and concentrations of BDE-47 (2,2′,4,4′-tetrabromodiphenyl ether), an environmental contaminant found in our food supply with adverse health impact. Our point-of-care diagnostic device utilizes flexible interdigitated carbon black electrodes to convert electric current into a microfluidic pump via gas bubble expansion during electrolytic reaction. The micropump receives power from a mobile phone and transports BDE-47 analytes through the microfluidic device conducting competitive ELISA. Using variable domain of heavy chain antibodies (commonly referred to as single domain antibodies or Nanobodies), the proposed device is sensitive for a BDE-47 concentration range of 10−3–104 μg/l, with a comparable performance to that uses a standard competitive ELISA protocol. It is anticipated that the potential impact in mobile detection of health and environmental contaminants will prove beneficial to our community and low-resource environments.
---
paper_title: A personalized food allergen testing platform on a cellphone.

paper_content:

We demonstrate a personalized food allergen testing platform, termed iTube, running on a cellphone that images and automatically analyses colorimetric assays performed in test tubes toward sensitive and specific detection of allergens in food samples. This cost-effective and compact iTube attachment, weighing approximately 40 grams, is mechanically installed on the existing camera unit of a cellphone, where the test and control tubes are inserted from the side and are vertically illuminated by two separate light-emitting-diodes. The illumination light is absorbed by the allergen assay, which is activated within the tubes, causing an intensity change in the acquired images by the cellphone camera. These transmission images of the sample and control tubes are digitally processed within 1 s using a smart application running on the same cellphone for detection and quantification of allergen contamination in food products. We evaluated the performance of this cellphone-based iTube platform using different types of commercially available cookies, where the existence of peanuts was accurately quantified after a sample preparation and incubation time of ~20 min per test. This automated and cost-effective personalized food allergen testing tool running on cellphones can also permit uploading of test results to secure servers to create personal and/or public spatio-temporal allergen maps, which can be useful for public health in various settings.
---
paper_title: Use of plastic-based analytical device, smartphone and chemometric tools to discriminate amines

paper_content:

Amine-based volatile compounds released by microorganisms offer an alternative diagnostic approach for the identification of foodborne pathogens. Our objective has been to solvent cast cellulose acetate membranes to immobilise dyes and to use the resultant membranes as a plastic device to discriminate between different types of amines (triethylamine, isobutylamine, isopentylamine). The plastic device consisted of an array of membranes with five pH indicators (namely alizarin, bromophenol blue, chlorophenol red, methyl red and thymol blue). To analyse the data using a portable instrument, we used an iPhone® to obtain images and to extract red, green and blue colours (RGB) using in-house software before and after contact with each individual amine. All the RGB values extracted for each analyte allowed us to generate a unique colour pattern, which was used as input for non-supervised pattern recognition methods. Based on this analysis, it was possible to clearly discriminate between the amines studied without any misclassification, demonstrating that the device is well-suited for large-scale applications such as non-destructive methods to discriminate amines and, in future, for smart packaging applications in order to give early warning of rotting food that may lead to food poisoning. Additionally, a semi-quantitative analysis was performed and we have demonstrated that it is possible to quantify concentrations of amines down to 1 ppm.
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paper_title: Performance Improvement of the One-Dot Lateral Flow Immunoassay for Aflatoxin B1 by Using a Smartphone-Based Reading System

paper_content:

This study was conducted to develop a simple, rapid, and accurate lateral flow immunoassay (LFIA) detection method for point-of-care diagnosis. The one-dot LFIA for aflatoxin B1 (AFB1) was based on the modified competitive binding format using competition between AFB1 and colloidal gold-AFB1-BSA conjugate for antibody binding sites in the test zone. A Smartphone-based reading system consisting of a Samsung Galaxy S2 Smartphone, a LFIA reader, and a Smartphone application for the image acquisition and data analysis. The detection limit of one-dot LFIA for AFB1 is 5 μg/kg. This method provided semi-quantitative analysis of AFB1 samples in the range of 5 to 1,000 μg/kg. Using combination of the one-dot LFIA and the Smartphone-based reading system, it is possible to conduct a more fast and accurate point-of-care diagnosis.
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paper_title: Optical Imaging of Paramagnetic Bead-DNA Aggregation Inhibition Allows for Low Copy Number Detection of Infectious Pathogens

paper_content:

DNA-paramagnetic silica bead aggregation in a rotating magnetic field facilitates the quantification of DNA with femtogram sensitivity, but yields no sequence-specific information. Here we provide an original description of aggregation inhibition for the detection of DNA and RNA in a sequence-specific manner following loop-mediated isothermal amplification (LAMP). The fragments generated via LAMP fail to induce chaotrope-mediated bead aggregation; however, due to their ability to passivate the bead surface, they effectively inhibit bead aggregation by longer ‘trigger’ DNA. We demonstrate the utility of aggregation inhibition as a method for the detection of bacterial and viral pathogens with sensitivity that approaches single copies of the target. We successfully use this methodology for the detection of notable food-borne pathogens Escherichia coli O157:H7 and Salmonella enterica, as well as Rift Valley fever virus, a weaponizable virus of national security concern. We also show the concentration dependence of aggregation inhibition, suggesting the potential for quantification of target nucleic acid in clinical and environmental samples. Lastly, we demonstrate the ability to rapidly detect infectious pathogens by utilizing a cell phone and custom-written application (App), making this novel detection modality fully portable for point-of-care use.
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paper_title: Disposable lateral flow-through strip for smartphone-camera to quantitatively detect alkaline phosphatase activity in milk.

paper_content:

A disposable lateral flow-through strip was developed for smartphone to fast one-step quantitatively detect alkaline phosphatase (ALP) activity in raw milk. The strip comprises two functional components, a conjugation pad loaded with phosphotyrosine-coated gold nanoparticles (AuNPs@Cys-Try-p) and a testing line coated with anti-phosphotryosine antibody (anti-Tyr-p mAb). The dephosphorylation activity of ALP at the testing zone can be quantitatively assayed by monitoring the accumulated AuNPs-induced color changes by smartphone camera, thus providing a highly convenient portable detection method. A trace amount of ALP as low as 0.1UL(-1) with a linear dynamic range of 0.1-150UL(-1) (R(2)=0.999) in pasteurized milk and raw milk can be one-step detected by the developed flow-through strip within 10min, demonstrating the potential of smartphone-based portable sensing device for pathogen detection. This bio-hazards free lateral flow-through testing strip can be also used to fabricate rapid, sensitive and inexpensive enzyme or immunosensors for broad portable clinic diagnosis and food contamination analysis, particularly in point-of-care and daily food quality inspection.
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paper_title: An iPhone-based digital image colorimeter for detecting tetracycline in milk

paper_content:

Abstract An iPhone-based digital image colorimeter (DIC) was fabricated as a portable tool for monitoring tetracycline (TC) in bovine milk. An application named ColorConc was developed for the iPhone that utilizes an image matching algorithm to determine the TC concentration in a solution. The color values; red (R), green (G), blue (B), hue (H), saturation (S), brightness (V), and gray (Gr) were measured from each pictures of the TC standard solutions. TC solution extracted from milk samples using solid phase extraction (SPE) was captured and the concentration was predicted by comparing color values with those collected in a database. The amount of TC could be determined in the concentration range of 0.5–10 μg mL −1 . The proposed DIC-iPhone is able to provide a limit of detection (LOD) of 0.5 μg mL −1 and limit of quantitation (LOQ) of 1.5 μg mL −1 . The enrichment factor was 70 and color of the extracted milk sample was a strong yellow solution after SPE. Therefore, the SPE-DIC-iPhone could be used for the assay of TC residues in milk at the concentration lower than LOD and LOQ of the proposed technique.
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paper_title: Paper microfluidics for red wine tasting

paper_content:

A paper microfluidic chip was designed and fabricated to evaluate the taste of 10 different red wines using a set of chemical dyes. The digital camera of a smartphone captured the images, and its red-green-blue (RGB) pixel intensities were analyzed by principal component analysis (PCA). Using 8 dyes and 2 principal components (PCs), we were able to distinguish each wine by the grape variety and the oxidation status. Through comparing with the flavor map by human evaluation, PC1 seemed to represent the sweetness and PC2 the bodyness of red wine. This superior performance is attributed to: (1) careful selection of commercially available dyes through a series of linear correlation studies with the taste chemicals in red wines, (2) minimization of sample-to-sample variation by splitting a single sample into multiple wells on the paper microfluidics, and (3) filtration of particulate matter through paper fibers. The image processing and PCA procedure can eventually be implemented as a stand-alone smartphone application and can be adopted as an extremely low-cost, disposable, fully handheld, easy-to-use, yet sensitive and specific quality control method for appraising red wine or similar beverage products in resource-limited environments.
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paper_title: Monitoring of fluoride in water samples using a smartphone.

paper_content:

In several parts of India, groundwater is the only reliable, year round source for drinking water. Prevention of fluorosis, a chronic disease resulting from excess intake of fluoride, requires the screening of all groundwater sources for fluoride in endemic areas. In this paper, the authors present a field deployable colorimetric analyzer based on an inexpensive smartphone embedded with digital camera for taking photograph of the colored solution as well as an easy-fit, and compact sample chamber (Akvo Caddisfly). Phones marketed by different smartphone makers were used. Commercially available zirconium xylenol orange reagent was used for determining fluoride concentration. A software program was developed to use with the phone for recording and analyzing the RGB color of the picture. Linear range for fluoride estimation was 0-2mgl(-1). Around 200 samples, which consisted of laboratory prepared as well as field samples collected from different locations in Karnataka, India, were tested with Akvo Caddisfly. The results showed a significant positive correlation between Ion Selective Electrode (ISE) method and Akvo Caddisfly (Phones A, B and C), with correlation coefficient ranging between 0.9952 and 1.000. In addition, there was no significant difference in the mean fluoride content values between ISE and Phone B and C except for Phone A. Thus the smartphone method is economical and suited for groundwater fluoride analysis in the field.
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paper_title: Use of plastic-based analytical device, smartphone and chemometric tools to discriminate amines

paper_content:

Amine-based volatile compounds released by microorganisms offer an alternative diagnostic approach for the identification of foodborne pathogens. Our objective has been to solvent cast cellulose acetate membranes to immobilise dyes and to use the resultant membranes as a plastic device to discriminate between different types of amines (triethylamine, isobutylamine, isopentylamine). The plastic device consisted of an array of membranes with five pH indicators (namely alizarin, bromophenol blue, chlorophenol red, methyl red and thymol blue). To analyse the data using a portable instrument, we used an iPhone® to obtain images and to extract red, green and blue colours (RGB) using in-house software before and after contact with each individual amine. All the RGB values extracted for each analyte allowed us to generate a unique colour pattern, which was used as input for non-supervised pattern recognition methods. Based on this analysis, it was possible to clearly discriminate between the amines studied without any misclassification, demonstrating that the device is well-suited for large-scale applications such as non-destructive methods to discriminate amines and, in future, for smart packaging applications in order to give early warning of rotting food that may lead to food poisoning. Additionally, a semi-quantitative analysis was performed and we have demonstrated that it is possible to quantify concentrations of amines down to 1 ppm.
---
paper_title: A sensing smartphone and its portable accessory for on-site rapid biochemical detection of marine toxins

paper_content:

Okadaic acid (OA) and saxitoxin (STX) are common marine toxins which can accumulate in shellfish and affect human health through the food chain. A convenient and efficient method is urgently required to perform on-site detection of marine toxins to avoid frequent poisoning incidents. In this work, a smartphone-based system cooperating with competitive immunoassay strips was designed for rapid on-site detection of OA and STX. The smartphone was employed as a light detector for image acquisition and data processing. The 3D-printed portable accessory of the smartphone was utilized to fix the test strips. The homemade APP – iStrip used the pixel scan to obtain the valley value of the pixel curve as the output of the strip. The strip analytical method was easy to operate with a detection limit of 2.800 ng ml−1 for OA and 9.808 ng ml−1 for STX. Moreover, with the optimization of the antigen–antibody ratio on the strip, it provided quantitative analysis of OA and STX in the range of 3–20 ng ml−1 and 10–100 ng ml−1, respectively. Taking advantage of the smartphone and biochemical analysis, the strip analytical system will be a promising tool for on-site rapid detection of these two toxins.
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paper_title: Food contamination monitoring via internet of things, exemplified by using pocket-sized immunosensor as terminal unit

paper_content:

Abstract Healthcare via internet-of-things (IoT) for protection against consumption of contaminated foods was demonstrated via immuno-analysis of pathogenic bacteria and the sharing of results using a mobile device. As wireless internet has spread widely over the world, it can be readily used to communicate information related to, for example, human health. Indeed, some institutes have demonstrated the measurement of physical vital signals (e.g., temperature, pulse, and heartbeat) of the body for monitoring through a smartphone. However, biochemical analytes such as proteins and bacteria are currently difficult to measure based on antigen-antibody binding due to several technological barriers. Among them, the terminal unit of detection for, for instance, pathogens is mostly bulky, insensitive, or even expensive for sophisticated devices. We have studied the use of CMOS image sensor (CIS) for detecting the signal produced from an immuno-analytical system, which could resolve the detection issue hindering monitoring via IoT. In this study, an immunosensor system using CIS for detection means was fabricated to pocket-sized dimensions and then employed for determining a food-borne pathogen, the Vibrio species, in real samples. The analysis was controlled and monitored using a smartphone that was also used to upload the result as data to the internet server for sharing with the public. To our knowledge, this study could be the first exemplification of pathogen monitoring via IoT in the field of healthcare.
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paper_title: A simple paper-strip colorimetric method utilizing dehydrogenase enzymes for analysis of food components

paper_content:

In this study, we present a simple chromatographic paper-based colorimetric assay for the analysis of selected food compounds. The biochemical principle utilises enzymes from the dehydrogenase family coupled with diaphorase in the presence of a tetrazolium dye, MTT, and NAD+. The colored reaction product that developed on the surface of the chromatography paper could either be qualitatively analysed by the naked eye, that is, it could be used for screening analysis, or it could be recorded by using a smartphone camera and evaluated in freeware ImageJ in order to obtain data for quantitative analysis. The general concept was demonstrated and optimised using (L)-glutamate dehydrogenase and the versatility of the proposed method was illustrated by using other enzymes from the dehydrogenase family. The linear range for (L)-glutamate was found to be 0.5–5.0 mmol L−1 using the digital image method. The limit of detection found by the naked eye was 0.05 mmol L−1 and 0.028 mmol L−1 by digital imaging. The paper assay stored in a freezer provided a reproducible response for at least 6 weeks. This research presents the successful modification of an MTT-cell viability test principle and its use in the fabrication of an inexpensive, easy to prepare, simple to use, portable and rapid-responding paper-based assay.
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paper_title: A smartphone-based colorimetric reader coupled with a remote server for rapid on-site catechols analysis

paper_content:

Abstract The search of a practical method to analyze cis-diol-containing compounds outside laboratory settings remains a substantial scientific challenge. Herein, a smartphone-based colorimetric reader was coupled with a remote server for rapid on-site analysis of catechols. A smallest-scale 2×2 colorimetric sensor array composed of pH indicators and phenylboronic acid was configured. The array was able to distinguish 13 catechols at 6 serial concentrations, through simultaneous treatment via principal component analysis, hierarchical cluster analysis, and linear discriminant analysis. After both the discriminatory power of the array and the prediction ability of the partial least squares quantitative models were proved to be predominant, the smartphone was coupled to the remote server. All the ΔRGB data were uploaded to the remote server wherein linear discriminant analysis and partial least squares processing modules were established to provide qualitative discrimination and quantitative calculation, respectively, of the analytes in real time. The applicability of this novel method to a real-life scenario was confirmed by the on-site analysis of various catechols from a water sample of the Yangtze River; the feedback result in the smartphone showed the method was able to identify the catechols with 100% accuracy and predict the concentrations to within 0.706–2.240 standard deviation.
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paper_title: Portable detection of clenbuterol using a smartphone-based electrochemical biosensor with electric field-driven acceleration

paper_content:

Abstract We have developed a fast, highly sensitive and low-cost biosensing system for the detection of clenbuterol (CLB), using a homemade mobile electrochemical device with an electric field-driven acceleration strategy. This system consists of an embedded circuit in smartphone for signal processing and a screen-printed carbon electrode (SPCE) modified with multi-walled carbon nanotubes (MWNTs) and goat anti mouse-immunoglobulin G (IgG) sensing layer (MWNTs-I-layer). CLB monoclonal antibody was assembled through its binding to the surface-confined antibody. Such modified electrodes were used for rapid and sensitive amperometric immunosensing detection of CLB. Horseradish peroxidase-coupled CLB (CLB–HRP) competed with free CLB in the samples to bind the monoclonal antibody. By using this mobile system, we could detect CLB ranging from 0.3 ng ⋅ mL − 1 to 100 ng ⋅ mL − 1 with the detection limit of 0.076 ng ⋅ mL − 1 . The whole competitive-type detection process was finished within 6 min. We expect this device can meet the requirements for field detection of various food security-related species.
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paper_title: Point-of-use electroanalytical platform based on homemade potentiostat and smartphone for multivariate data processing

paper_content:

Abstract We herein report a potential point-of-use platform for multivariate analyses by presenting homemade potentiostat and smartphone. This system combined high-performance detection (linear sweep, cyclic, and square wave voltammetry) with great simplicity, low-cost, portability, autonomy (6 h), and cable-free (wireless communication) device. In addition, the smartphone showed ability for processing complex and multivariate data. To the best of our knowledge, this paper is the first reporting about the development of a totally integrated point-of-use system with chemometric data processing on smartphone. This feature is essential for in-situ assays by allowing the real-time accomplishment of the entire analytical measurement at remote places. Such ability further reduces the occurrence of model overfitting by non-expert users. As proof-of-concept, our system was successfully applied to fingerprint Brazilian honey samples according to their botanical and geographic origins. The method relied on the unsupervised technique of principal component analysis (PCA) and the assays were performed by cyclic voltammetry using a single and non-modified working electrode of gold.
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paper_title: Mini and micro spectrometers pave the way to on-field advanced analytics

paper_content:

First introduced in the 1990's, miniature optical spectrometers were compact, portable devices brought on the market by the desire to move from time-consuming lab-based analyses to on-field and in situ measurements. This goal of getting spectroscopy into the hands of non-specialists is driving current technical and application developments, the ultimate goal being, in a far future, the integration of a spectrometer into a smartphone or any other smart device (tablet, watch, …). In this article, we present the results of our study on the evolution of the compact spectrometers market towards widespread industrial use and consumer applications. Presently, the main market of compact spectrometers remains academic labs. However, they have been adopted on some industrial applications such as optical source characterization (mainly laser and LEDs). In a near future, manufacturers of compact spectrometers target the following industrial applications: agriculture crop monitoring, food process control or pharmaceuticals quality control. Next steps will be to get closer to the consumer market with point-of-care applications such as glucose detection for diabetics, for example. To reach these objectives, technological breakthroughs will be necessary. Recent progresses have already allowed the release of micro-spectrometers. They take advantage of new micro-technologies such as MEMS (MicroElectroMechanical Systems), MOEMS (Micro-Opto-Electro-Mechanical Systems), micro-mirrors arrays to reduce cost and size while allowing good performance and high volume manufacturability. Integrated photonics is being investigated for future developments. It will also require new business models and new market approaches. Indeed, spreading spectroscopy to more industrial and consumer applications will require spectrometers manufacturers to get closer to the end-users and develop application-oriented products.
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paper_title: Detection of fecal contamination on beef meat surfaces using handheld fluorescence imaging device (HFID)

paper_content:

Current meat inspection in slaughter plants, for food safety and quality attributes including potential fecal contamination, is conducted through by visual examination human inspectors. A handheld fluorescence-based imaging device (HFID) was developed to be an assistive tool for human inspectors by highlighting contaminated food and food contact surfaces on a display monitor. It can be used under ambient lighting conditions in food processing plants. Critical components of the imaging device includes four 405-nm 10-W LEDs for fluorescence excitation, a charge-coupled device (CCD) camera, optical filter (670 nm used for this study), and Wi-Fi transmitter for broadcasting real-time video/images to monitoring devices such as smartphone and tablet. This study aimed to investigate the effectiveness of HFID in enhancing visual detection of fecal contamination on red meat, fat, and bone surfaces of beef under varying ambient luminous intensities (0, 10, 30, 50 and 70 foot-candles). Overall, diluted feces on fat, red meat and bone areas of beef surfaces were detectable in the 670-nm single-band fluorescence images when using the HFID under 0 to 50 foot-candle ambient lighting.
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paper_title: Optical Imaging of Paramagnetic Bead-DNA Aggregation Inhibition Allows for Low Copy Number Detection of Infectious Pathogens

paper_content:

DNA-paramagnetic silica bead aggregation in a rotating magnetic field facilitates the quantification of DNA with femtogram sensitivity, but yields no sequence-specific information. Here we provide an original description of aggregation inhibition for the detection of DNA and RNA in a sequence-specific manner following loop-mediated isothermal amplification (LAMP). The fragments generated via LAMP fail to induce chaotrope-mediated bead aggregation; however, due to their ability to passivate the bead surface, they effectively inhibit bead aggregation by longer ‘trigger’ DNA. We demonstrate the utility of aggregation inhibition as a method for the detection of bacterial and viral pathogens with sensitivity that approaches single copies of the target. We successfully use this methodology for the detection of notable food-borne pathogens Escherichia coli O157:H7 and Salmonella enterica, as well as Rift Valley fever virus, a weaponizable virus of national security concern. We also show the concentration dependence of aggregation inhibition, suggesting the potential for quantification of target nucleic acid in clinical and environmental samples. Lastly, we demonstrate the ability to rapidly detect infectious pathogens by utilizing a cell phone and custom-written application (App), making this novel detection modality fully portable for point-of-care use.
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paper_title: Ultra-portable, wireless smartphone spectrometer for rapid, non-destructive testing of fruit ripeness

paper_content:

We demonstrate a smartphone based spectrometer design that is standalone and supported on a wireless platform. The device is inherently low-cost and the power consumption is minimal making it portable to carry out a range of studies in the field. All essential components of the device like the light source, spectrometer, filters, microcontroller and wireless circuits have been assembled in a housing of dimensions 88 mm × 37 mm × 22 mm and the entire device weighs 48 g. The resolution of the spectrometer is 15 nm, delivering accurate and repeatable measurements. The device has a dedicated app interface on the smartphone to communicate, receive, plot and analyze spectral data. The performance of the smartphone spectrometer is comparable to existing bench-top spectrometers in terms of stability and wavelength resolution. Validations of the device were carried out by demonstrating non-destructive ripeness testing in fruit samples. Ultra-Violet (UV) fluorescence from Chlorophyll present in the skin was measured across various apple varieties during the ripening process and correlated with destructive firmness tests. A satisfactory agreement was observed between ripeness and fluorescence signals. This demonstration is a step towards possible consumer, bio-sensing and diagnostic applications that can be carried out in a rapid manner.
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paper_title: Development of a Handheld Spectrometer Based on a Linear Variable Filter and a Complementary Metal-Oxide-Semiconductor Detector for Measuring the Internal Quality of Fruit

paper_content:

Visible and near infrared spectroscopy has long been used to predict fruit internal quality, with portable instrumentation advantageous for in-field use. We developed a handheld spectrometer using a linear variable filter (LVF) and a complementary metal-oxide-semiconductor (CMOS) linear detector array. The LVF is a bandpass filter with a centre wavelength changing linearly in one direction and can replace a grating as the light-dispersion component. An LVF was designed and fabricated specifically to work in the 620–1080 nm region and for the analysis of fruit. The optical design used an improved collimator and an LVF to yield a compact, stable and low-cost optical engine. By using a CMOS detector and other suitable electronics, the spectrometer achieved a low power consumption. The spectrometer can analyse spectral data using an onboard prediction model and can be operated from a remote smartphone, tablet or laptop computer. This paper details the design of the spectrometer and the results of its resoluti...
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paper_title: Diffractive interference optical analyzer (DiOPTER)

paper_content:

This report demonstrates a method for high-resolution refractometric measurements using, what we have termed as, a Diffractive Interference Optical Analyzer (DiOpter). The setup consists of a laser, polarizer, a transparent diffraction grating and Si-photodetectors. The sensor is based on the differential response of diffracted orders to bulk refractive index changes. In these setups, the differential read-out of the diffracted orders suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6x10(-7) RIU was achieved in glass. This work focuses on devices with integrated sample well, made on low-cost PDMS. As the detection methodology is experimentally straightforward, it can be used across a wide array of applications, ranging from detecting changes in surface adsorbates via binding reactions to estimating refractive index (and hence concentration) variations in bulk samples. An exciting prospect of this technique is the potential integration of this device to smartphones using a simple interface based on transmission mode configuration. In a transmission configuration, we were able to achieve an LoD of 4x10(-4) RIU which is sufficient to explore several applications in food quality testing and related fields. We are envisioning the future of this platform as a personal handheld optical analyzer for applications ranging from environmental sensing to healthcare and quality testing of food products.
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paper_title: SpiderSpec: a low-cost compact colorimeter with IoT functionality

paper_content:

A miniaturized device for colorimetry is presented that utilizes a LED array for illumination and a compact spectrometer for detection. It can be battery-powered, operated locally as a stand-alone device, or connected via wi-fi to the internet. It has potentials to be remotely operated by means of a tablet or a smartphone. In practice, it consists of a low-cost hardware configuration that is adaptable via software to the user’s most varied requests, as a spectroscopic platform appropriate for a variety of applications. The hardware and software modules can be designed with different performances, complexities and costs, with the aim of making the colorimeter a device for Internet-of-Things use. It will be suitable for a selected range of consumer applications, as well as for targeted industrial, environmental, and food applications.
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paper_title: Proposal of AAA-battery-size one-shot ATR Fourier spectroscopic imager for on-site analysis: Simultaneous measurement of multi-components with high accuracy

paper_content:

For simultaneous measurement of multi-components on-site like factories, the ultra-compact (diameter: 9[mm], length: ::: 45[mm], weight: 200[g]) one-shot ATR (Attenuated Total Reflection) Fourier spectroscopic imager was proposed. ::: Because the proposed one-shot Fourier spectroscopic imaging is based on spatial-phase-shift interferometer, ::: interferograms could be obtained with simple optical configurations. We introduced the transmission-type relativeinclined ::: phase-shifter, that was constructed with a cuboid prism and a wedge prism, onto the optical Fourier transform ::: plane of infinity corrected optical systems. And also, small light-sources and cameras in the mid-infrared light region, ::: whose size are several millimeter on a side, are essential components for the ultra-compact spectroscopic configuration. ::: We selected the Graphite light source (light source area: 1.7×1.7[mm], maker: Hawkeye technologies) whose radiation ::: factor was high. Fortunately, in these days we could apply the cost-effective 2-dimensional light receiving device for ::: smartphone (e.g. product name: LEPTON, maker: FLIR, price: around 400USD). In the case of alcoholic drinks factory, ::: conventionally workers measure glucose and ethanol concentrations by bringing liquid solution back to laboratories ::: every day. The high portable spectroscopy will make it possible to measure multi-components simultaneously on ::: manufacturing scene. But we found experimentally that absorption spectrum of glucose and water and ethanol were ::: overlapped each other in near infrared light region. But for mid-infrared light region, we could distinguish specific ::: absorption peaks of glucose (@10.5[μm]) and ethanol (@11.5[μm]) independently from water absorption. We obtained ::: standard curve between absorption (@9.6[μm]) and ethanol concentration with high correlation coefficient 0.98 ::: successfully by ATR imaging-type 2-dimensional Fourier spectroscopy (wavelength resolution: 0.057[μm]) with the ::: graphite light source (maker: Hawkeye technologies, type: IR-75).
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paper_title: Monitoring of fluoride in water samples using a smartphone.

paper_content:

In several parts of India, groundwater is the only reliable, year round source for drinking water. Prevention of fluorosis, a chronic disease resulting from excess intake of fluoride, requires the screening of all groundwater sources for fluoride in endemic areas. In this paper, the authors present a field deployable colorimetric analyzer based on an inexpensive smartphone embedded with digital camera for taking photograph of the colored solution as well as an easy-fit, and compact sample chamber (Akvo Caddisfly). Phones marketed by different smartphone makers were used. Commercially available zirconium xylenol orange reagent was used for determining fluoride concentration. A software program was developed to use with the phone for recording and analyzing the RGB color of the picture. Linear range for fluoride estimation was 0-2mgl(-1). Around 200 samples, which consisted of laboratory prepared as well as field samples collected from different locations in Karnataka, India, were tested with Akvo Caddisfly. The results showed a significant positive correlation between Ion Selective Electrode (ISE) method and Akvo Caddisfly (Phones A, B and C), with correlation coefficient ranging between 0.9952 and 1.000. In addition, there was no significant difference in the mean fluoride content values between ISE and Phone B and C except for Phone A. Thus the smartphone method is economical and suited for groundwater fluoride analysis in the field.
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paper_title: MEMS FPI-based smartphone hyperspectral imager

paper_content:

This paper demonstrates a mobile phone- compatible hyperspectral imager based on a tunable MEMS Fabry-Perot interferometer. The realized iPhone 5s hyperspectral imager (HSI) demonstrator utilizes MEMS FPI tunable filter for visible-range, which consist of atomic layer deposited (ALD) Al2O3/TiO2-thin film Bragg reflectors. Characterization results for the mobile phone hyperspectral imager utilizing MEMS FPI chip optimized for 500 nm is presented; the operation range is λ = 450 – 550 nm with FWHM between 8 – 15 nm. Also a configuration of two cascaded FPIs (λ = 500 nm and λ = 650 nm) combined with an RGB colour camera is presented. With this tandem configuration, the overall wavelength tuning range of MEMS hyperspectral imagers can be extended to cover a larger range than with a single FPI chip. The potential applications of mobile hyperspectral imagers in the vis-NIR range include authentication, counterfeit detection and potential health/wellness and food sensing applications.
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paper_title: Point-of-use electroanalytical platform based on homemade potentiostat and smartphone for multivariate data processing

paper_content:

Abstract We herein report a potential point-of-use platform for multivariate analyses by presenting homemade potentiostat and smartphone. This system combined high-performance detection (linear sweep, cyclic, and square wave voltammetry) with great simplicity, low-cost, portability, autonomy (6 h), and cable-free (wireless communication) device. In addition, the smartphone showed ability for processing complex and multivariate data. To the best of our knowledge, this paper is the first reporting about the development of a totally integrated point-of-use system with chemometric data processing on smartphone. This feature is essential for in-situ assays by allowing the real-time accomplishment of the entire analytical measurement at remote places. Such ability further reduces the occurrence of model overfitting by non-expert users. As proof-of-concept, our system was successfully applied to fingerprint Brazilian honey samples according to their botanical and geographic origins. The method relied on the unsupervised technique of principal component analysis (PCA) and the assays were performed by cyclic voltammetry using a single and non-modified working electrode of gold.
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paper_title: Rapid and reagentless detection of microbial contamination within meat utilizing a smartphone-based biosensor

paper_content:

Rapid and reagentless detection of microbial contamination within meat utilizing a smartphone-based biosensor
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paper_title: Cellphone-based detection platform for rbST biomarker analysis in milk extracts using a microsphere fluorescence immunoassay

paper_content:

Current contaminant and residue monitoring throughout the food chain is based on sampling, transport, administration, and analysis in specialized control laboratories. This is a highly inefficient and costly process since typically more than 99% of the samples are found to be compliant. On-site simplified prescreening may provide a scenario in which only samples that are suspect are transported and further processed. Such a prescreening can be performed using a small attachment on a cellphone. To this end, a cellphone-based imaging platform for a microsphere fluorescence immunoassay that detects the presence of anti-recombinant bovine somatotropin (rbST) antibodies in milk extracts was developed. RbST administration to cows increases their milk production, but is illegal in the EU and a public health concern in the USA. The cellphone monitors the presence of anti-rbST antibodies (rbST biomarker), which are endogenously produced upon administration of rbST and excreted in milk. The rbST biomarker present in milk extracts was captured by rbST covalently coupled to paramagnetic microspheres and labeled by quantum dot (QD)-coupled detection antibodies. The emitted fluorescence light from these captured QDs was then imaged using the cellphone camera. Additionally, a dark-field image was taken in which all microspheres present were visible. The fluorescence and dark-field microimages were analyzed using a custom-developed Android application running on the same cellphone. With this setup, the microsphere fluorescence immunoassay and cellphone-based detection were successfully applied to milk sample extracts from rbST-treated and untreated cows. An 80% true-positive rate and 95% true-negative rate were achieved using this setup. Next, the cellphone-based detection platform was benchmarked against a newly developed planar imaging array alternative and found to be equally performing versus the much more sophisticated alternative. Using cellphone-based on-site analysis in future residue monitoring can limit the number of samples for laboratory analysis already at an early stage. Therewith, the entire monitoring process can become much more efficient and economical.
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paper_title: Smartphone-interfaced lab-on-a-chip devices for field-deployable enzyme-linked immunosorbent assay

paper_content:

The emerging technologies on mobile-based diagnosis and bioanalytical detection have enabled powerful laboratory assays such as enzyme-linked immunosorbent assay (ELISA) to be conducted in field-use lab-on-a-chip devices. In this paper, we present a low-cost universal serial bus (USB)-interfaced mobile platform to perform microfluidic ELISA operations in detecting the presence and concentrations of BDE-47 (2,2′,4,4′-tetrabromodiphenyl ether), an environmental contaminant found in our food supply with adverse health impact. Our point-of-care diagnostic device utilizes flexible interdigitated carbon black electrodes to convert electric current into a microfluidic pump via gas bubble expansion during electrolytic reaction. The micropump receives power from a mobile phone and transports BDE-47 analytes through the microfluidic device conducting competitive ELISA. Using variable domain of heavy chain antibodies (commonly referred to as single domain antibodies or Nanobodies), the proposed device is sensitive for a BDE-47 concentration range of 10−3–104 μg/l, with a comparable performance to that uses a standard competitive ELISA protocol. It is anticipated that the potential impact in mobile detection of health and environmental contaminants will prove beneficial to our community and low-resource environments.
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paper_title: Optical Imaging of Paramagnetic Bead-DNA Aggregation Inhibition Allows for Low Copy Number Detection of Infectious Pathogens

paper_content:

DNA-paramagnetic silica bead aggregation in a rotating magnetic field facilitates the quantification of DNA with femtogram sensitivity, but yields no sequence-specific information. Here we provide an original description of aggregation inhibition for the detection of DNA and RNA in a sequence-specific manner following loop-mediated isothermal amplification (LAMP). The fragments generated via LAMP fail to induce chaotrope-mediated bead aggregation; however, due to their ability to passivate the bead surface, they effectively inhibit bead aggregation by longer ‘trigger’ DNA. We demonstrate the utility of aggregation inhibition as a method for the detection of bacterial and viral pathogens with sensitivity that approaches single copies of the target. We successfully use this methodology for the detection of notable food-borne pathogens Escherichia coli O157:H7 and Salmonella enterica, as well as Rift Valley fever virus, a weaponizable virus of national security concern. We also show the concentration dependence of aggregation inhibition, suggesting the potential for quantification of target nucleic acid in clinical and environmental samples. Lastly, we demonstrate the ability to rapidly detect infectious pathogens by utilizing a cell phone and custom-written application (App), making this novel detection modality fully portable for point-of-care use.
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paper_title: Ultra-portable, wireless smartphone spectrometer for rapid, non-destructive testing of fruit ripeness

paper_content:

We demonstrate a smartphone based spectrometer design that is standalone and supported on a wireless platform. The device is inherently low-cost and the power consumption is minimal making it portable to carry out a range of studies in the field. All essential components of the device like the light source, spectrometer, filters, microcontroller and wireless circuits have been assembled in a housing of dimensions 88 mm × 37 mm × 22 mm and the entire device weighs 48 g. The resolution of the spectrometer is 15 nm, delivering accurate and repeatable measurements. The device has a dedicated app interface on the smartphone to communicate, receive, plot and analyze spectral data. The performance of the smartphone spectrometer is comparable to existing bench-top spectrometers in terms of stability and wavelength resolution. Validations of the device were carried out by demonstrating non-destructive ripeness testing in fruit samples. Ultra-Violet (UV) fluorescence from Chlorophyll present in the skin was measured across various apple varieties during the ripening process and correlated with destructive firmness tests. A satisfactory agreement was observed between ripeness and fluorescence signals. This demonstration is a step towards possible consumer, bio-sensing and diagnostic applications that can be carried out in a rapid manner.
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paper_title: Monitoring of fluoride in water samples using a smartphone.

paper_content:

In several parts of India, groundwater is the only reliable, year round source for drinking water. Prevention of fluorosis, a chronic disease resulting from excess intake of fluoride, requires the screening of all groundwater sources for fluoride in endemic areas. In this paper, the authors present a field deployable colorimetric analyzer based on an inexpensive smartphone embedded with digital camera for taking photograph of the colored solution as well as an easy-fit, and compact sample chamber (Akvo Caddisfly). Phones marketed by different smartphone makers were used. Commercially available zirconium xylenol orange reagent was used for determining fluoride concentration. A software program was developed to use with the phone for recording and analyzing the RGB color of the picture. Linear range for fluoride estimation was 0-2mgl(-1). Around 200 samples, which consisted of laboratory prepared as well as field samples collected from different locations in Karnataka, India, were tested with Akvo Caddisfly. The results showed a significant positive correlation between Ion Selective Electrode (ISE) method and Akvo Caddisfly (Phones A, B and C), with correlation coefficient ranging between 0.9952 and 1.000. In addition, there was no significant difference in the mean fluoride content values between ISE and Phone B and C except for Phone A. Thus the smartphone method is economical and suited for groundwater fluoride analysis in the field.
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paper_title: Point-of-use electroanalytical platform based on homemade potentiostat and smartphone for multivariate data processing

paper_content:

Abstract We herein report a potential point-of-use platform for multivariate analyses by presenting homemade potentiostat and smartphone. This system combined high-performance detection (linear sweep, cyclic, and square wave voltammetry) with great simplicity, low-cost, portability, autonomy (6 h), and cable-free (wireless communication) device. In addition, the smartphone showed ability for processing complex and multivariate data. To the best of our knowledge, this paper is the first reporting about the development of a totally integrated point-of-use system with chemometric data processing on smartphone. This feature is essential for in-situ assays by allowing the real-time accomplishment of the entire analytical measurement at remote places. Such ability further reduces the occurrence of model overfitting by non-expert users. As proof-of-concept, our system was successfully applied to fingerprint Brazilian honey samples according to their botanical and geographic origins. The method relied on the unsupervised technique of principal component analysis (PCA) and the assays were performed by cyclic voltammetry using a single and non-modified working electrode of gold.
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paper_title: Cellphone-based detection platform for rbST biomarker analysis in milk extracts using a microsphere fluorescence immunoassay

paper_content:

Current contaminant and residue monitoring throughout the food chain is based on sampling, transport, administration, and analysis in specialized control laboratories. This is a highly inefficient and costly process since typically more than 99% of the samples are found to be compliant. On-site simplified prescreening may provide a scenario in which only samples that are suspect are transported and further processed. Such a prescreening can be performed using a small attachment on a cellphone. To this end, a cellphone-based imaging platform for a microsphere fluorescence immunoassay that detects the presence of anti-recombinant bovine somatotropin (rbST) antibodies in milk extracts was developed. RbST administration to cows increases their milk production, but is illegal in the EU and a public health concern in the USA. The cellphone monitors the presence of anti-rbST antibodies (rbST biomarker), which are endogenously produced upon administration of rbST and excreted in milk. The rbST biomarker present in milk extracts was captured by rbST covalently coupled to paramagnetic microspheres and labeled by quantum dot (QD)-coupled detection antibodies. The emitted fluorescence light from these captured QDs was then imaged using the cellphone camera. Additionally, a dark-field image was taken in which all microspheres present were visible. The fluorescence and dark-field microimages were analyzed using a custom-developed Android application running on the same cellphone. With this setup, the microsphere fluorescence immunoassay and cellphone-based detection were successfully applied to milk sample extracts from rbST-treated and untreated cows. An 80% true-positive rate and 95% true-negative rate were achieved using this setup. Next, the cellphone-based detection platform was benchmarked against a newly developed planar imaging array alternative and found to be equally performing versus the much more sophisticated alternative. Using cellphone-based on-site analysis in future residue monitoring can limit the number of samples for laboratory analysis already at an early stage. Therewith, the entire monitoring process can become much more efficient and economical.
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paper_title: Mobile Phone-Based Microscopy, Sensing, and Diagnostics

paper_content:

Mass production of consumer electronics devices and market competition have provided users with cost-effective, compact, and high-performance products with high-end components including digital cameras, graphics processing units, and various sensors. This opened up the opportunity for researchers, and even citizen scientists, to develop novel imaging, sensing, and diagnostics platforms using mobile phones as an underlying platform. Mobile phones’ hardware and software technical capabilities, wireless connectivity, and wide-spread use, in billions, have made them ideal, especially to address the global demand for accurate, sensitive, cost-effective, and field-portable measurement devices that can be used in remote and resource-limited settings around the world. This Review focuses on these recent advances in the use of mobile phone-based imaging and sensing techniques for point of care applications, including microscopy and diagnostic testing. The achievements demonstrated so far illustrate the potential to globally transform and democratize measurement science in general, with a significant impact for scientists, engineers, and educators.
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Title: Smartphone-Based Food Diagnostic Technologies: A Review

Section 1: Introduction 
Description 1: This section provides an overview of the increasing importance of mobile diagnostics in various sectors and the potential benefits of smartphone-based food diagnostic technologies.

Section 2: Results
Description 2: This section categorizes and details the various smartphone-based food diagnostic approaches.

Section 3: Lab-On-Smartphone Biosensors
Description 3: This section discusses biosensors that integrate with smartphones for detecting analytes of interest.

Section 4: Fluorescence Imaging Using Smartphone
Description 4: This section explains the use of smartphones for fluorescence imaging in food diagnostics.

Section 5: Smartphone-Based Colorimetric Readers
Description 5: This section covers colorimetric assays using smartphone cameras to detect the presence of various analytes in food samples.

Section 6: Smartphone-Based Electro-Analytical Platforms
Description 6: This section discusses electroanalytical methods using smartphones to measure the electrical parameters of analyte solutions.

Section 7: Smartphone Spectroscopy
Description 7: This section reviews the use of smartphones in optical diagnostics and spectroscopy for non-invasive food analysis.

Section 8: Emerging Market of Smartphone-Based Food Diagnostic Platforms
Description 8: This section highlights the current market and emerging start-ups offering smartphone-based food diagnostic platforms.

Section 9: Approximate Cost Reference
Description 9: This section provides an approximate cost comparison for various smartphone-based food diagnostic technologies.

Section 10: Discussion
Description 10: This section discusses challenges and considerations for ensuring the reliability and repeatability of measurements using smartphone-based diagnostic platforms.

Section 11: Conclusions
Description 11: This section summarizes the developments, potential, and future directions of smartphone-based food diagnostics.