Role of extracellular polymeric substances in the adhesion interaction of Streptococcus mutans on TiO2 and SiO2 surfaces with different wettability

The purpose of the work is to evaluate the effect of extracellular polymeric substance (EPS) on the surface properties of Streptococcus mutans, and on the interaction between the bacteria and anti-adhesion nanostructured surfaces. Interactions between Streptococcus mutans with or without EPS and nanostructured surfaces were measured with atomic force microscope. Acid-base, Van der Waals, and electrostatic interactions were evaluated according to XDLVO theory. The absorption of glucan was evaluated by quartz crystal microbalance method. Results indicate Streptococcus mutans adhere stronger on surfaces with lower surface energy in both EPS and non EPS conditions, because acid-base interaction is dominant. It indicates the superhydrophobic surface is lack of durability and reliability in the underwater anti-adhesion. Larger adhesion forces of Streptococcus mutans are shown in EPS than non-EPS conditions. That is due to more hydrogen bonds formed between glucan and sub strate surfaces, and the EPS reducing surface energy and affecting acid-base interaction.