Investigation of polysaccharide adsorption on protein conditioning films by attenuated total reflection infrared spectrometry - II. Thin copper films

The study of microorganisms at the aqueous/metal interface is of great inte rest as their presence is often associated with surface deterioration or co rrosion. Surfaces submerged in aquatic environments rapidly become fouled w ith organic macromolecules, such as proteins and/or glycoproteins. Bacteria adhering to this conditioning film typically produce extracellular polysac charides that anchor the cells to the substrate. In a previous paper, the k inetics of polysaccharide adsorption and desorption on protein conditioning films formed on bare germanium internal reflection elements (IREs) were in vestigated in an effort to gain a better understanding of the fouling proce ss. This work has been extended to the study of adsorption phenomena at an aqueous/copper interface. Alginic acid and dextran were exposed to protein- conditioned and untreated copper films. In the absence of a protein biofilm , greater erosion of the Cu film was observed with flowing saline than with a solution of alginic acid in saline, and more Cu was removed at pH 4.8 th an at pH 7.0. The neutral polysaccharide was less corrosive than alginic ac id. The presence of a film of bovine serum albumin (13.5 nm) conditioning f ilm did not shield the Cu film from the corrosive effects of either polysac charide. In all experiments, as Cu slowly eroded from the surface of the IR E, metal islands formed leading to the observation of surface-enhanced infr ared absorption (SEIRA). The intensity of the C-O stretching band of adsorb ed dextran on Cu islands was over an order of magnitude greater than would be observed with a uniform Cu him of the same thickness. Enhancement of the amide II band of BSA was also observed. In general, the effect of SEIRA co mplicated spectral processing and interpretation and thus interfered with t he determination of surface coverage and polysaccharide adsorption/desorpti on kinetics on protein conditioning films. (C) 1999 Academic Press.