Nanofiber Composites of Poly(vinyl alcohol)/Silver-Based Molybdate and Tungstate Oxide Semiconductors for Antimicrobial Applications.

In the present study, powders of α-Ag₂WO₄ (PAW) and β-Ag₂MoO₄ (PAM) were prepared through the coprecipitation method, while poly(vinyl alcohol) nanofibers (FPVA) and composite nanofibers of PVA/α-Ag₂WO₄ (FPAW) and PVA/β-Ag₂MoO₄ (FPAM) were prepared using the electrospinning technique. Several characterization techniques were applied to evaluate the structure of the obtained materials, as well as studies for assessing their antimicrobial properties. The antimicrobial activities of the composites against Pseudomonas aeruginosa and Staphylococcus aureus were investigated through the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Our studies demonstrated that materials exhibit antibacterial activity against P. aeruginosa (MIC/MBC = 0.014/ND mg mL^-1 for PAW; MIC/MBC = 1.43/1.43 for PAM; MIC/MBC = 1.35/1.35 mg mL^-1 for FPAW; MIC/MBC = 3.68/11.03 mg mL^-1 for FPAM and MIC/MBC = 8.78/ND mg mL^-1 for FPVA) and S. aureus (MIC/MBC = 0.794/ND mg mL^-1 for PAW; MIC/MBC = 1.43/ND for PAM; MIC/MBC = 1.35/1.35 mg mL^-1 for FPAW; MIC/MBC = 3.68/3.67 mg mL^-1 FPAM and MIC/MBC = 14.63/* mg mL^-1 for FPVA). The cytotoxic concentrations (CC₅₀, μg mL^-1) against the VERO cells were 21.74 ± 0.04 for PAW, <15 for PAM, 103.70 ± 18.90 for FPAW, 111.22 ± 4.02 for FPAM, and >1000 for FPVA, thus indicating that the immobilization of the semiconductor to the FPVA mats decreases the cytotoxic effect of the materials studied as compared to not immobilized ones. The results suggest that powders and composite polymeric mats displayed antimicrobial action that was attributed to the production of reactive oxygen species (ROS), which are responsible for inducing high local oxidative stress, causing the death of both types of bacteria.