pH-Triggered in-situ release of silver nanoparticle in hydrogel for topical applications

Silver nanoparticle (AgNP) has potent anti-microbial activity & chitosan has wound healing activity. L-Glutamic acid is a wound healing promoting agent. So AgNP & L-glutamic acid loaded chitosan hydrogel would be a promising formulation for topical applications like wound healing. But instability of AgNP is the main problem to develop such a topical gel. We synthesized AgNP conjugated chitosan microparticle (SNCCM) as a stable source of AgNP. In aqueous medium, the release of AgNP was triggered at pH ≤ 4.5. The optimum pH was 4.5. The released AgNP was of ∼27 nm size. The SNCCM particles had 9.86 × 10 12 AgNP conjugated per mg of dried product. The geometric mean diameter of dried SNCCM particles was 590 ± 1.0 μ m, whereas the average weight was 0.51 ± 0.05 mg. So, exact number of SNCCM particles can be dissolved in aqueous medium of pH 4.5 to get the desired dose of AgNP in-situ . The optimum gel had pH of 4.5 & particle content of 1.47 × 10 13 AgNP ml −1 . The viscosity and spreadibility of hydrogel were 22 780 ± 1.24 cp and 20 ± 4.7 gm-cm/s respectively. The hydrogel was equally effective against both Gram +ve and Gram −ve bacteria. The diameters of its zone of inhibition were 37.62 ± 3.04 mm against S. aureus & 37.65 ± 2.97 mm against E. coli.