Effects of anionic and cationic surfactants on the rheological properties and kinetics of bovine serum albumin hydrogel

Abstract

The effects of the anionic surfactant, sodium dodecyl sulfate (SDS), and of the cationic surfactant cetyltrimethylammonium bromide (CTAB) on the gelation kinetics of bovine serum albumin (BSA) hydrogel were investigated by rheological measurements using surfactant concentrations of 0–0.05 M, and BSA concentrations of 5, 7, and 10 wt%. It was found while an increase in CTAB concentration accelerated the rate of gelation of BSA solution under temperature jump and temperature ramp conditions, BSA solutions containing SDS exhibited a heat-dependent protective effect against thermal denaturation and gelation. Under temperature ramp conditions, inhibition of BSA gelation by SDS was diminished by increasing SDS concentration, while under temperature jump conditions, inhibition of BSA gelation increased with SDS concentration. That is, gel temperature (Tgel) under temperature ramp decreased with increasing CTAB and with SDS concentration, but under temperature jump the gel time (tgel) decreased with increasing CTAB concentration but increased with SDS concentration. Furthermore, BSA/CTAB solutions were found to gel more rapidly than BSA/SDS solutions, which was in line with the lower activation energy of BSA/CTAB gel. In support of experiments, molecular dynamics (MD) simulations and dynamic light scattering (DLS) revealed the faster rate of BSA denaturation in the presence of CTAB was responsible for the increased gelation rate of BSA/CTAB solutions, whereas BSA was found to be protected by SDS against thermal denaturation leading to the slower gelation rate of BSA/SDS solutions.