E. coli adhesion and biofilm formation on polydimethylsiloxane are independent of substrate stiffness

Bacterial adhesion and biofilm formation on the surface of biomedical devices is a detrimental process that compromises patient safety and material functionality. Several physicochemical factors are involved in biofilm growth, including the surface properties. Among those, material stiffness has recently been suggested to influence microbial adhesion and biofilm growth in a variety of polymers and hydrogels. However, no clear consensus exists about the role of material stiffness on biofilm initiation and whether very compliant substrates are deleterious to bacterial cell adhesion. Here, by systematically tuning substrate topography and stiffness while keeping the surface free energy of polydimethylsiloxane substrates constant, we show that topographical patterns at the micron and submicron scale impart unique properties to the surface that are independent of the material stiffness. The current work provides a better understanding of the role of material stiffness on bacterial physiology and may constitute a cost-effective and simple strategy to reduce bacterial attachment and biofilm growth even in very compliant and hydrophobic polymers.