Silver/poly(vinyl alcohol)/graphene hydrogels for wound dressing applications: Understanding the mechanism of silver, antibacterial agent release

Long-term wound healing and chronic wound care represent significant challenges for biomaterials science and engineering with many diverse requirements for the wound dressing properties, as well as antibacterial efficacy and antibacterial agent release to prevent and treat persistent infections. Silver nanoparticles, as a wide-spectrum antibacterial agent that does not induce bacterial resistance, are very convenient for use as an active component in antibacterial hydrogel wound dressing materials with the controlled release ability. In this work, we aim to perform a comprehensive analysis of silver release from poly(vinyl alcohol)-based hydrogels with electrochemically synthesized antibacterial silver nanoparticles (AgNPs), aimed for wound dressing applications. Different AgNPs concentrations were loaded in hydrogel matrices using the green electrochemical reduction method, and thus synthesized nanocomposite hydrogels were characterized by different techniques (scanning electron microscopy, Fourier-transform infrared and Raman spectroscopy, and differential scanning calorimetry), in order to assess their physico-chemical and thermal properties. Silver release was monitored for 28 days in physiologically-relevant conditions (phosphate buffered medium, pH 7.4, 37°C). The obtained experimental data were evaluated against several theoretical release models (Korsmeyer-Peppas, Higuchi, Makoid-Banakar, Kopcha, and early-time approximation), which confirmed the predominantly diffusion-controlled mechanism of release. Finally, AgNP-loaded hydrogels were assessed for antibacterial activity against Staphylococcus aureus TL and Escherichia coli ATCC25922 bacterial strains, to prove their strong potential for wound dressing applications.