Soft hydrogels obtained by photothermal curing of poly(vinylpyrrolidone)/gold nanoparticles dispersions showing anisotropic swelling and photo-activated antimicrobial properties

Poly(vinylpyrrolidone) (PVP) hydrogels were obtained by green light irradiation of aqueous PVP/ammonium persulfate solutions modified with gold nanoparticles (AuNPs). The increase in temperature produced through the activation of the photothermal effect of AuNPs triggers the decomposition of ammonium persulfate producing radicals that, by attacking the polymer main chain and generating macro-radicals, induce the crosslinking of the polymer via recombination paths. Irradiation from the top of the solutions in an open configuration produced water evaporation and a concomitant increase in temperature during curing, giving rise to dry materials with high aspect ratio and moderate swelling anisotropy. Pads that reversibly adhere to different substrates, including human skin, were produced by simple contact of the final materials with water. Impregnation of gauze wound dressings with PVP-Au-ammonium persulfate dispersions, followed by direct “in situ” photothermal crosslinking, enabled the fabrication of supported functional pads with potential applications as reversible adhesive skin wound dressings. Infusion of the hydrogels with Rose Bengal (RB) provides the materials with photosensitizing properties useful for the photodynamic inactivation of Staphylococcus aureus. A decrease in cell viability of 99.9% was attained after 30 min of irradiation with a low-power green LED source, which demonstrates the efficient singlet oxygen production by RB in the hydrogels and paves the way towards the design of new stimulus-activated bactericidal supplies for biomedical uses.