On the adsorption kinetics of bovine serum albumin at the air-water interface

The adsorption kinetics of bovine serum albumin (BSA) at an air-water interface was investigated by experimentally measuring and theoretically modeling the dynamic surface tension (ST) data. A pendant bubble tensiometer was utilized for two ST measurements: (i) the adsorption onto a freshly created bubble surface and (ii) the bubble expansion/compression at the latter stage. The dynamic ST data, during the early stage of BSA adsorption, were best-fitted with the short-time approximation equation (diffusioncontrol) and the non-asymptomatic short-time formalism [mixed-control, Moorkanikkara and Blankschtein, JCIS, 296, 442-457 (2006)]. The fitting showed that the non-asymptotic short-time formalism could well predict the dynamic ST data; thereby, implying that the adsorption of BSA onto a clean air-water interface was mixed-controlled. A new approach for estimating the maximum surface concentration (Gamma(infinity)) and the intermolecular interaction amongst the adsorbed BSA molecules (K) was trialed. The relaxation of ST during a surface expansion was best-fitted with the Langmuir/Frumkin equation of state. A reasonably good fitting between the dynamic ST data and the theoretical ST profiles indicated that this approach could be used to estimate the F and K for BSA without requiring the equilibrium ST data. (C) 2022 Elsevier B.V. All rights reserved.