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Description
Upon exposure to saliva, solid surfaces in the oral cavity are rapidly covered by a bacteria-free pellicle, mainly composed of proteins and polysaccharides. This presents the first step in oral biofilm formation. Despite its importance for subsequent bacterial adhesion, the quantitative contribution of its components remains poorly understood. While protein adsorption has been extensively studied, polysaccharides in mixed biomolecular adsorption layers are difficult to quantify because, spectroscopic signals may overlap and matrix effects complicate component-specific analysis [1,2].
Bovine serum albumin (BSA) and dextran (70 kDa) were used as a simplified model system to investigate simultaneous adsorption on silicon surfaces, which resemble a flat, hydrophilic, oxide-covered surface. For component-specific quantification, direct UV-based determination of BSA in the low UV range was combined with an indirect sulfuric acid-based UV assay for dextran [3]. Ion-exchange chromatography seperated both components prior to quantification, thereby minimizing matrix effects and improving analytical reliability.
The optimized approach was applied to adsorption experiments at different BSA-dextran ratios and pH values. The results were complemented by quartz crystal microbalance measurements and force spectroscopy. The adsorbed-layer composition strongly depended on solution conditions. Both BSA and dextran were detected, with relative contributions varying with pH and mixing ratio.
Together with previous studies on strongly and weakly bound fractions in biomolecular adsorption layers, these findings suggest that BSA-dextran layers contain components with different binding strengths [publication in preparation]. The methodology provides a robust basis for more reliable component-specific quantification of mixed protein-polysaccharid adsorption layers and highlights the relevance of polysaccharides in simplified pellicle-like model systems.
