Polyvinyl alcohol (PVA) hydrogels are materials for potential use in burn healing. Silver nanoparticles can be synthesized within PVA hydrogels giving antimicrobial hydrogels. Hydrogels have to be swollen prior to their application, and the common medium available for that in hospitals is saline solution, but the hydrogel could also take up some of the wound's fluid. This work developed gamma-irradiated PVA/nano-Ag hydrogels for potential use in burn dressing applications. Silver nitrate (AgNO 3 ) was used as nano-Ag precursor agent. Saline solution, phosphate-buffered solution (PBS) pH 7.4 and solution pH 4.0 were used as swelling media. Microstructural evaluation revealed an effect of the nanoparticles on PVA crystallization. The swelling of the PVA-Ag samples in solution pH 4.0 was low, as was their silver delivery, compared with the equivalent samples swollen in the other media. The highest swelling and silver delivery were related to samples prepared with 0.50% AgNO 3 , and they also presented lower strength in PBS pH 7.4 and solution pH 4.0. Both PVA-Ag samples were also non-toxic and presented antimicrobial activity, confirming that 0.25% AgNO 3 concentration is sufficient to establish an antimicrobial effect. Both PVA-Ag samples presented suitable mechanical and swelling properties in all media, representative of potential burn site conditions.

PVA hydrogels offer many suitable characteristics for burn wound dressings. However, unmodified PVA gels do not act against infection. Propolis is a natural antimicrobial agent suitable for incorporation into PVA gels. PVA-propolis gels were produced by freeze-thawing method, and their microstructure, mechanical, and swelling properties (in standard PBS and a PBS-based solution with pH 4.0) were characterized. The propolis release profiles and the gel's antibacterial and cytotoxicity properties were also investigated. The presence of propolis in the gels interfered with the PVA crystallization profile and with the mechanical properties. All samples swelled at least 400% in both media. The propolis was mostly released to the media in the first day of immersion. PVA-propolis gels with concentrations of 15% propolis or more were active against the gram-positive bacterium Staphylococcus aureus, which is associated with initial colonization of the wound. All PVA-propolis samples acted as barriers to microbial penetration.