Adhesion force measurement at L-cystine crystal surfaces

L-cystine kidney stones are a hereditary disorder that affects at least 20,000 people in the United States alone. Traditional treatments for the disease are somewhat effective but often lead to adverse side-effects and in some cases fail to prevent reappearance of the stones. To find an effective cure for the disease it is important to understand the mechanism in which the L-cystine crystals grow, form an aggregate and attach to the renal cells. Urinary proteins and bio-macromolecules play an important role in stone formation by becoming intercalated between crystals and may either promote or disrupt the aggregation and attachment stages.

In the Ward group we attempt to mimic these interactions by measuring adhesion forces between tip immobilized molecules and L-cystine crystal surfaces using Atomic Force Microscopy (AFM). The primary stage of the project relies on determining the interaction of a single functional group (e.g. COOH, NH2, OH etc.) with different faces of the L-cystine crystal. To achieve this, self assembled monolayer (SAM) of organo-sulfur compounds are created on gold-coated Si3N4 AFM tips through the formation of Au-S bond. These functionalized tips are then brought into contact with different faces of L-cystine crystals in an aqueous environment and the adhesion forces are measured. In future, we aim to extend our measurement to urinary macromolecules to follow the exact nature of interaction between these molecules and L-cystine crystal surfaces at the molecular level.