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Harry Potter meets nano-medicine


Cloaking can be used to make drug-carrying nanoparticles invisible, say researchers (Source: Institut Paoli Calmettes/AMU/CNRS/INSERM)


Applied mathematician Dr Sebastien Guenneau and biologist Dr Tania Puvirajesinghe, of Marseille University, report their findings in today's issue of the Journal of the Royal Society Interface.

"Here, we suggest a novel application to the fast-growing research area of cloaking ... to diffusion processes in biophysics," write the researchers.

"This could have advantages in increasing drug stability for longer circulation times."

Australian theoretical physicist Professor Ross McPhedran, from the University of Sydney, says the husband and wife team have used the standard methods of cloaking, which is best known as a means of making objects invisible.

In this application of cloaking, metamaterials guide light waves around an object, says McPhedran, who co-authored a previous paper with Guenneau.

He likens what happens to light waves in cloaking to water flowing around a rock.

The water closest to the rock travels slower than the water travelling further away, says McPhedran, so that when the water rejoins, it does so smoothly, as if the rock had never been there in the first place.

But cloaking is not just restricted to electromagnetic waves, he says.

"Indeed the payoffs may be easier and bigger in other fields apart from light."

Multi-layered cloak

In this case, the researchers have used cloaking principles to model a "multi-layered cloak" that can make a nanoparticle containing a water-soluble drug invisible to the bloodstream, protecting it from breakdown by the immune system, and allowing it to get safely to its target.

Instead of electromagnetic waves, the cloak guides the flow of immune cells so they don't spread (diffuse) into the nanoparticle, and it also ensures the drug molecules don't diffuse out until they reach their target.

"They're defining a diffusion cloak which guides the chemical concentrations of the immune cells to flow around the cloaked region rather than through it," says McPhedran.

He says concentric layers in the cloak are responsible for controlling the rate at which chemicals diffuse across it, and when the time is right the nanoparticle can be "uncloaked".

"The [drug] you want to be able to deliver has to be able to diffuse out when it's in the right place."

McPhedran says uncloaking could occur in response to some environmental change, for example pH.

Guenneau is also involved in developing earthquake cloaks, which are foundations that protect buildings by guiding seismic waves around them.

Tags: health, physics, nanotechnology