Polypropylene prostheses coated with silver nanoclusters/silica coating obtained by sputtering: Biocompatibility and antibacterial properties

With the goal of preventing abdominal infections after implanting prostheses for hernia repair, polypropylene prostheseswere coated with a silver nanoclusters-silica composite (Ag/SiO2) layer, by means of a sputtering process, to confer antibacterial properties. The Ag/SiO2 coating was deposited, with good uniformity and adhesion, either onto hernia prostheses (CMC) made of two polypropylene layers (macroporous light mesh and thin transparent film), or onto the mesh layer alone. The coating was optimized to achieve a good balance between antibacterial activity and biocompatibility. Antibacterial activity, fibroblast growth on CMC/mesh layer alone, in the presence/absence of Ag/SiO2, collagen, and some cytokines involved in inflammation and healing processes, were determined. Preliminary experiments showed that when both layers of CMC were entirely coated, antibacterial properties were achieved while losing prosthesis biocompatibility. Coating the entire CMC was a complex process, thus for subsequent experiments the mesh layer alone was coated, being the antibacterial properties unaffected by this choice and the mesh the part of CMC exposed to possible infection. With a duty cycle of 1 s over 24 on an Ag target, for 15 min deposition time, antibacterial activity, evaluated through the quantitative Colony–Forming Units test,was positive; fibroblasts colonized the coated mesh layer and produced collagen. Cell viability analysis showed that most cells were viable at all experimental times. Moreover, IL-1β and IL-6 decreased, and TGF-β2 increased, in fibroblasts seeded on mesh layer coated with Ag/SiO2 versus that without Ag/SiO2. Ag/SiO2-coated mesh layers allowed fibroblast growth and activity, without inducing cell death via apoptosis or necrosis and, at the same time, provided antibacterial activity.