Study of Bacterial Adhesion on Different Glycopolymer Surfaces by Quartz Crystal Microbalance with Dissipation

Protein–carbohydrate interactions are involved in a wide variety of cellular recognition processes including cell growth regulation, differentiation and adhesion, the immune response, and viral or bacterial infections. A common way for bacteria to achieve adhesion is through their fimbriae which possess cellular lectins that can bind to complementary carbohydrates on the surface of the host tissues. In this work, we synthesized glycopolymers using reversible addition–fragmentation chain transfer (RAFT) polymerization which were subsequently immobilized on a sensor surface for studies of bacterial adhesion by quartz crystal microbalance with dissipation (QCM-D). Ricinus communis Agglutinin (RCA120), a galactose specific lectin, was first studied by QCM-D to determine the specific lectin interactions to the different glycopolymers-treated surfaces. Subsequently, Pseudomonas aeruginosa PAO1 (a Gram-negative bacterium with galactose-specific binding C-type lectin (PA-IL)) and Escherichia coli K-12 (a Gram-negative bacterium with mannose-specific binding lectin) were then used as model bacteria to study bacterial adhesion mechanisms on different polymer-treated sensor surfaces by the coupled resonance theory. Our results showed that lectin–carbohydrate interactions play significant roles in comparison to the nonspecific interactions, such as electrostatic interactions. A significantly higher amount of P. aeruginosa PAO1 could adhere on the glycopolymer surface with strong contact point stiffness as compared to E. coli K-12 on the same surface. Furthermore, in comparison to E. coli K-12, the adhesion of P. aeruginosa PAO1 to the glycopolymers was found to be highly dependent on the presence of calcium ions due to the specific C-type lectin interactions of PA-IL, and also the enhanced bacterial adhesion is attributed to the stiffer glycopolymer surface in higher ionic strength condition.