Bacteria Adhesion on Polydimethylsiloxane Surfaces Impacted by Material Viscoelasticity or Surface Chemistry?

Among nosocomial infections, materials associated infections are the most frequent and severe due to biofilm formation. To prevent bacterial colonization, understanding the underlying interaction between bacteria and surface is fundamental. Herein we focused on studying how material viscoelasticity and physicochemistry can influence bacterial adhesion, using polydimethylsiloxane (PDMS) as a model material. To delineate the impact caused by bulk material from interfacial physicochemical properties, a 2 nm PDMS-like polymer layer was coated onto PDMS surfaces of different stiffness to confer comparable surface chemical properties, while retaining similar viscoelasticity for coated and uncoated PDMS species. Although the uncoated samples displayed increasing interfacial adhesion force with the decreasing Young's modulus, the nanolayer coating ensured comparable forces independent of material stiffness. The Gram negative strains Escherichia coli and Pseudomonas aeruginosa and the Gram positive strain Staphylococcus epidermidis were found to adhere respectively in similar numbers on the coated surfaces of different PDMS species, whereas the amount on the uncoated surfaces increased several fold with the decreasing modulus. The similar adhesion behaviour was noticed for abiotic polystyrene beads of similar size to bacteria, demonstrating that the interfacial chemistry of the PDMS rather than the material viscoelasticity plays a crucial role in bacterial adhesion.