Study of the interactions of proteins with a solid surface using complementary acoustic and optical techniques.

Membrane water treatment processes suffer severely from (bio)fouling phenomena, defined as an undesired deposition and build-up of adsorbed materials, which alters the membrane performance. The control of membrane (bio)fouling is directly related to first the (bio)foulant agent-membrane surface interactions arising at a much earlier stage during the process. This study aims at real time characterization of interaction between proteins and polymeric membrane surface. The adsorbed organic mass, water content, and the corresponding viscoelastic properties of adsorbed proteins on the polymeric membrane surface were investigated by combining the acoustic quartz crystal microbalance with dissipation monitoring technique with the optical surface plasmon resonance technique. Bovine serum albumin (BSA) and avidin were used as model protein, and a polysulfone (PSU) was included as reference polymeric membrane. The results showed that both proteins tested were irreversibly adsorbed on the spin-coated polysulfone surface. The "dry" amount of irreversible BSA and avidin adsorbed on the PSU surface was found to be 292 and 380 ng/cm(2), respectively, and the corresponding water contents were 50% and 58%. Consequently, BSA adsorption on the PSU surface yielded a thinner, flat, and more compact (rigid) layer while avidin adsorbed in a thicker layer with higher surface mass density, a more diffuse, viscoelastic layer, and in addition, it undergoes larger conformational/orientational changes.