Bacterial adhesion on polyelectrolyte multilayers

It is known that bacteria readily adhere to various surfaces and, therefore, bacterial adhesion can be controlled by different material surface properties. The factors that affect the intensity of bacterial adhesion include surface roughness, surface charge, and degree of hydrophobicity, Lewis acid-base character, and hydrogen-bonding capacity. Environmental factors including pH, temperature, nutrient composition and population characteristics may enhance the adhesion and biofilm maturation. In our study we focus on the surface charge. Using layer-by- layer technique we prepared various surfaces with different terminating layers. We used the silica surface on which poly(allylamine hydrochloride)/sodium poly(4-styrenesulfonate) (PAH/PSS) polyelectrolyte multilayers were formed. The surface charge was examined by the zeta potential measurements of silica particles covered with polyelectrolyte multilayers, whereby ionic strength and polyelectrolyte concentrations significantly influenced the build-up process. The corresponding surface roughness and hydrophobicity were determined by atomic force microscopy and tensiometry. For adhesion experiments, we used the bacterium Pseudomonas aeruginosa. The extent of adhered bacteria on the surface was determined by scanning electron microscopy. The results showed [2] that the extent of adhered bacteria mostly depends on the charge of terminating polyelectrolyte layer, since relatively low differences in surface roughness and hydrophobicity were obtained. This study has shown the importance of combining surface characterization with microbial testing to understand the bacteria-surface interactions. The application of polyelectrolyte multilayers with tunable electrostatic properties enables the preparation of the surfaces with desirable properties in terms of bacterial adhesion.