Species-Specific Bacterial Responses to Partially Oil-Infused Silicone Polymers

Liquid-infused polymers are of interest in biomedical applications due to their robust antifouling properties. Currently, it is broadly accepted that their effectiveness stems from a free-flowing and continuous liquid layer on the surface. However, recent studies have shown that partially infused polymers, which have limited or no surface liquid layer, can still effectively repel foulants, indicating that we do not yet fully understand the mechanisms behind this system. To begin unraveling the potential mechanisms by which liquid-infused materials repel foulants, we infused silicone polymers with silicone oil to various saturation levels, incubated them with Escherichia coli, Enterococcus faecalis, and Pseudomonas aeruginosa, and measured adhesion and colonization. Our findings revealed that after 48 h of incubation, cells of E. coli showed a low degree of overall surface colonization, with a significant decrease only at 90% oil saturation or above. Interestingly, E. coli cells adhered more firmly to polymers with 10–30% oil saturation than oil-free controls. In contrast, E. faecalis was more resistant to removal, showing decreased colony counts only at 70–90% saturation and significantly reduced adhesion at 30–50% saturation. P. aeruginosa also showed low colonization with a significant decrease at 70–90%. However, adhesion was significantly impacted at only 10–30% infusion. Overall, our results suggest that oil saturation levels can be key factors influencing the complex interaction between liquid-infused surfaces and bacterial adhesion and that different species respond to these surfaces in different ways, providing important information for adapting these materials for use in different applications.