Fibril formation kinetics of insulin solutions in an interfacial shearing flow

The formation of amyloid fibril plaques and the accumulation of such structures in vivo is the hallmark of disorders such as Alzheimer’s and type-II diabetes. Fibril formation can be accelerated by several factors including changes to pH and temperature conditions. However, the role of the dominant and most varying in vivo factors of fluid flow and shear at hydrophobic interfaces in protein aggregation pathways remain poorly understood. Proteins adsorbed at the air/fluid interface are also subjected to significant hydrodynamic stresses during bioprocessing and drug handling, which leads to unwarranted denaturation/aggregation and subsequent loss in drug efficacy. Here, we study the kinetics of fibril formation for human recombinant insulin solutions in an interfacial shearing flow using fixed time-point ThT fluorescence and native-protein absorbance assays across a wide range of rotation rates. We identify differences in the morphology of the fibril structures formed at the air/fluid interface and in bulk solution at different stages of fibril seeding and growth. This is key to elucidating the aggregation pathway and toxicity of shear-induced denaturation and protein fibril formation.