Effect of Interfacial Aggregation Layers on Rheological Properties in Protein Solutions

Human follicular fluid (HFF) collected during assisted reproductive technology procedures is a complex fluid exhibiting shear-thinning properties. We have investigated the dependence of shear viscosity of HFF on the developmental state of the oocyte. However, the role of interfacial rheology of proteins in HFF affecting its viscosity characteristics remains unclear. In the present study, we evaluated the effect of interfacial aggregation layers formed by proteins on the rheological properties by measuring the shear viscosity, extensional viscosity, and dynamic/static surface tension of HFF and protein solutions. Albumin and fibrinogen, which are abundant in HFF, were employed as the contained proteins. The shear viscosity of all solutions varied depending on the type of rotational rheometers such as coaxial double cylindrical rotary rheometer and cone-plate rheometer, while the extensional viscosity measured using an extensional rheometer employing the liquid dripping method was not affected by the interfacial rheology of interfacial aggregation layers.