Abstract
PVA films with embedded either silver nanoparticles (AgNP), NIR-absorbing photothermal gold nanostars (GNS), or mixed AgNP+GNS were prepared in this research. The optimal conditions to obtain stable AgNP+GNS films with intact, long lasting photothermal GNS were obtained. These require coating of GNS with a thiolated polyethylene glycol (PEG) terminated with a carboxylic acid function, acting as reticulant in the film formation. In the mixed AgNP+GNS films, the total noble metal content is <0.15% w/w and in the Ag films < 0.025% w/w. The slow but prolonged Ag+ release from film-embedded AgNP (8–11% of total Ag released after 24 h, in the mixed films) results in a very strong microbicidal effect against planktonic Escherichia coli and Staphylococcus aureus bacterial strains (the release of Au from films is instead negligible). Beside this intrinsic effect, the mixed films also exert an on-demand, fast hyperthermal bactericidal action, switched on by NIR laser irradiation (800 nm, i.e., inside the biotransparent window) of the localized surface plasmon resonance (LSPR) absorption bands of GNS. Temperature increases of 30 °C are obtained using irradiances as low as 0.27 W/cm2. Moreover, 80–90% death on both strains was observed in bacteria in contact with the GNS-containing films, after 30 min of irradiation. Finally, the biocompatibility of all films was verified on human fibroblasts, finding negligible viability decrease in all cases.
Highlights
The normalized tensile work values, calculated as the area under the curve (AUC) force vs. deformation distance (Figure 4B), confirm this behaviour, i.e., an increase in film mechanical resistance is observed for films containing gold nanostars (GNS)@polyethylene glycol (PEG)-C with respect to those cross-linked with citric acid
We found the correct synthetic conditions to allow AgNP and GNS to coexist in the same precursor solution, from which PVA films containing both nanoparticles were obtained
All films containing AgNP, GNS or both revealed of being capable of exerting an intrinsic, prolonged antibacterial action, due to the release of
Summary
Functional silane monolayers (b and e) were needed to graft GNS to the underlying glass surface (a) and AgNP to the SiO2 layer (d) This material exerted a strong intrinsic antibacterial effect due to the spherical AgNP (d = 8 nm) on the top layer, plus a strong hyperthermal antibacterial effect when the LSPR band of the embedded GNS was excited with an 800 nm laser source. In the frame of our recent interest for nanoinorganic-based antibacterial products to be used in the treatment of wounds [32,33], we have prepared, for the first time, a flexible film containing both small spherical AgNP and photothermally active GNS, i.e., a film capable of both intrinsic and switchable antibacterial action. Absorption spectra were recorded on a HP8453 spectrophotometer, either in solution in 1 mm and 1 cm glass cuvettes or directly on films, by means of a dedicated sample holder
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
