Hybrid Chitosan/PVA Hydrogels Incorporating Silver Nanoparticles as Antibacterial Polymeric Dressings

Silver nanoparticles are widely incorporated into polymer dressings, but the effect of the nanoparticle synthesis conditions on the final material is rarely compared within one polymer matrix. Here, citrate-stabilized Ag NPs were prepared by NaBH4 reduction using two reductant volumes (400 and 1000 µL) and incorporated into the same chitosan (CH)/poly(vinyl alcohol) (PVA) matrix cast with citric acid. UV-Vis, DLS, STEM, AFM and XRD showed face-centered cubic Ag NPs with mean diameters of 27 ± 5 nm (1000 µL) and 38 ± 6 nm (400 µL) by STEM, with the same trend by DLS and AFM. Their antibacterial effect was assessed using agar diffusion tests. In agar diffusion tests, the smaller Ag NPs gave larger inhibition zones against Escherichia coli and Staphylococcus aureus The corresponding hydrogel with smaller Ag NPs confirmed the antibacterial tests performed on nanoparticles and gave larger inhibition zones for both bacterial strains. The integration of Ag NPs in hydrogels was confirmed by SEM-EDX mapping, while their integrity was assessed using swelling tests and Ag NPs release tests. In PBS, all films, including the Ag-free control, remained intact for 48 h, with the highest swelling ratio for CH/PVA/Ag-NaBH4 1000.After 24 h in PBS at 37 °C, about 75% (CH/PVA/Ag-NaBH4 1000) and 53% (CH/PVA/Ag-NaBH4 400) of the incorporated Ag NPs were released. The CH/PVA/Ag-NaBH4 1000 formulation is therefore the more promising candidate to be considered a favorable antibacterial polymeric dressing.