Observed widely in nature, biofilm formation in medical and industrial contexts has proven inevitable, expensive, and occasionally dangerous. The controlled adsorption of the well-understood protein model poly-L-lysine (PLL) and subsequent deposition of the polysaccharide alginate to functionalized silica can provide insight into the mechanisms of biofilm formation. On a hydrophilic silanol surface, PLL films are compact and their formation governed by electrostatic interactions; film thickness and continuity reached a maximum at intermediate solution ionic strength, decreasing with additional salt concentration. Alginate film thickness and continuity were correlated with the homogeneity of the underlying PLL film. By contrast, the PLL films adsorbed to hydrophobic silane surfaces were much thicker and were most continuous at low polymer molecular weights, but alginate film thickness and homogeneity did not appear to follow that of the underlying PLL film. Through a combination of ellipsometric film thickness and dynamic contact angle measurement, data on both the average layer thickness adsorbed and film continuity was gathered, allowing a more complete picture of the structure and surface chemistry of PLL and alginate films. It was clearly demonstrated that the properties of the underlying surface effects both the formation of the PLL film and subsequent alginate adsorption. Future work will focus upon explaining these data through examination of film homogeneity and composition through AFM imaging and ATR IR spectroscopy studies.
Brown, Jennie, "Understanding biofilm formation : poly-L-lysine mediated adsorption of alginate to functionalized silica surfaces" (2008). Honors Project, Smith College, Northampton, MA.
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