pH-dependent swelling and antibiotic release from citric acid crosslinked poly(vinyl alcohol) (PVA)/nano silver hydrogels

In this work, a pH-sensitive and antibacterial drug delivery system based on poly(vinyl alcohol) (PVA)/citric acid (CA)/Ag nanoparticles (NPs) was designed using a completely green, facile and one-step route. Interestingly, the crosslinking of PVA with CA, and in-situ formation of Ag NPs within the polymeric matrix were simultaneously and simply carried out using an annealing process without need for any toxic chemicals. The developed hydrogels were characterized by FTIR, UV-vis spectra, SEM and TEM techniques. It was found that CA not only acted as a crosslinker of PVA via esterification reaction, but also it endowed pH-responsiveness and antibacterial activity to the PVA matrix due to presence of free carboxylic acid groups on CA. Hydrogels demonstrated a pHdependent swelling as well as drug release behavior, as the swelling ratio and the drug release at pH 7.4 were found higher than pH 1.2. Furthermore, the release of ciprofloxacin was more sustained when Ag NPs were incorporated into hydrogels. In addition, the incorporation of CA, Ag NPs and ciprofloxacin into the PVA matrix provided an effective antibacterial activity against E. coli and S. aureus microorganisms. The developed hydrogels can be considered as a promising material in the prolonged antibiotic therapy such as intestinal infection treatment.