Role of Characteristics of External Mechanical Stress and Substrate on the Characteristics of Insulin Aggregates

Abstract

The role of chemical nature of the surface and mechanical stress on the properties of insulin in solution kept in the container is explored. The mechanical stress can be applied in the form of shear force or shaking of content in vials. The process of shear can be continuous or intermittent periodic stoppage of shear. We have observed the secondary structures of insulin present over the surface and in the solution. In addition, we have observed the distribution of insulin size, which arises due to their aggregation in solution. The properties are found to depend on the processes of applying mechanical force on a solution. The conversions of α-helix to β-sheet for continuous shear, but to intermolecular β-sheet in presence of the interrupted shear are found. The later phenomenon leads to the formation of a bigger particle. The shaking of the content of vials leads to the formation of particles with the higher random coil. The combined effect of shaking and chemical nature of surface on the aggregates’ properties is also observed. The size distribution and secondary structures of aggregates of insulin in solution are strongly dependent on the chemical nature of the surface. These are explained through desorption of the adsorbed protein. The higher rate desorption of protein from lesser hydrophobic surfaces leads to the formation of bigger insulin aggregates.