Surface-enhanced nucleation of insulin amyloid fibrillation

Proteins can interact with biological surfaces such as cell membrane, chaperones, cornea, bone, arteries, veins, and heart cavities of the cardiovascular system and also with non-biological surfaces including dialysis membranes and tubing, catheters, invasive surgical instruments, needles, and artificial implants. Fibrillation of amyloid proteins is implicated in many human diseases, including Alzheimer's, Parkinson's, and type II diabetes. Here, we show that heterogeneous surfaces accelerate the human insulin nucleation process that is the rate-determining step during amyloid fibril formation. The observed shorter lag (nucleation) phase correlates both with surface wettability and surface roughness. Surfaces promote faster nucleation possibly by increasing the local concentration of protein molecules. A composite parameter combining both surface wettability and roughness suggests that the ideal surface for slower nucleation should be hydrophilic and smooth. These findings provide a basis for designing suitable biomaterials and biomedical devices, especially those to resist amyloidosis.