A nanolayer coating on polydimethylsiloxane surfaces enables a mechanistic study of bacterial adhesion influenced by material surface physicochemistry

Abstract

To control material-associated bacterial infections, understanding the underlying mechanisms of bacteria and surface interactions is essential. Here we focused on studying how material mechanical and chemical properties can impact bacterial adhesion, using polydimethylsiloxane (PDMS) as a model material. To this end, PDMS surfaces of different stiffness were coated with a 2 nm highly cross-linked PDMS-like polymer film to confer comparable surface chemistry, while retaining similar mechanical properties for coated and uncoated samples. The uncoated samples showed increased interfacial adhesion force with the decrease of Young's modulus, whereas the nanolayer deposition yielded a comparable adhesion force for all surfaces. The Gram negative strains Escherichia coli, its fimbriae mutants and Pseudomonas aeruginosa as well as the Gram positive strain Staphylococcus epidermidis were analysed for their adhesion on these surfaces. For each bacterial strain similar numbers were found on the coated surfaces of different PDMS species, whereas the numbers on the uncoated surfaces increased several fold with the decrease of material modulus. Similar adhesion behaviour was also observed for the negatively charged abiotic polystyrene beads of similar size to bacteria. These results strongly suggest that the interfacial chemistry of the PDMS rather than the material mechanical properties plays a critical role in bacterial adhesion.