Stable, bioactive hydrogel coating on silicone surfaces for non-invasive decontamination via photochemical treatment

Polydimethylsiloxane (PDMS) is widely used in biomedical applications due to its biocompatibility, chemical stability, flexibility, and resistance to degradation in physiological environments. However, its intrinsic inertness limits further (bio)functionalization, and its hydrophobic recovery compromises the longevity of conventional surface modifications. To address these challenges, we developed a nanoprecipitation method for the straightforward colloidal deposition, covalent thermal crosslinking, and surface anchoring of a chemically tunable, biocompatible polyacrylamide with reactive hydroxyl groups, enabling further surface modifications. This polymer incorporates ~6% bioinspired catechol units, introduced via an elegant one-pot Kabachnik-Fields reaction, to facilitate thermally induced network formation and enhance adhesion to plasma-activated PDMS. The resulting uniform coatings exhibited tunable dry layer thicknesses up to 44 ± 7 nm and effectively suppressed PDMS chain rearrangement even after steam autoclaving, ensuring long-term stability in aqueous and ambient environments for at least 60 days. The bioactive post-modification potential was demonstrated in a proof-of-concept study by immobilizing the photosensitizer rose bengal at surface concentrations of 20 or 40 µg cm⁻². The coating exhibited antimicrobial activity against S. aureus, achieving a 4-log reduction (99.99%) in colony-forming units after 30 minutes of irradiation at 554 nm (342 J cm⁻²), even when bacteria were suspended in liquid, without direct surface contact. In contrast, antimicrobial activity against E. coli was only observed when the liquid volume was minimized, bringing the motile bacteria into close contact with the surface. This work established a straightforward and versatile strategy for the stable and bioactive functionalization of PDMS surfaces for application in non-invasive surface decontamination.