Pectin-capped gold nanoparticles synthesis in-situ for producing durable, cytocompatible, and superabsorbent hydrogel composites with chitosan

Studies report the production of gold nanoparticles (AuNPs) and polysaccharides-based composites. However, there are few reports about AuNPs synthesis in-situ followed by the formation of hydrogel composites. Here, we show AuNPs synthesis in-situ into the pectin solutions to yield cytocompatible pectin-capped AuNPs/chitosan hydrogel composites. Visible spectroscopy and dynamic light scattering measurements confirm the AuNPs synthesis. The hydrodynamic radius of the pectin-capped AuNPs ranges from approximately 510 to 721 nm, while the Zeta potential is around −43 mV. Scanning electron microscopy shows that the composites present compact structures. Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy characterize the composites as well. Hydrogels (with or without AuNPs) containing the highest pectin content (at 4.12 pectin/chitosan weight ratio) have low stability (disintegrates approximately 60% after 14 days in phosphate buffer). Composites obtained at 3.75 pectin/chitosan weight ratio disintegrate between 25 and 30% after 14 days in phosphate buffer (physiological condition = pH 7.4). The AuNPs reinforce the hydrogel structures, increasing the elastic modulus (from 3.5 to 7.6 Pa) and decreasing the water uptake from 4465 to 2976%. 3.75 PT/CS weight ratio and 3.0 × 10−4 M Au(III) content provide a durable, cytocompatible, and superabsorbent hydrogel composite. These properties can support materials for drug delivery purposes. [Display omitted] •Pectin-capped gold nanoparticle/chitosan hydrogel composites are synthesized in-situ.•The gelation is achieved by tuning the pectin/chitosan ratio and Au(III) concentration.•The optimized condition provides a durable, cytocompatible, and superabsorbent composite.•Pectin and a composite can stabilize the gold nanoparticles over 90 days of storage at 25 °C.•We suggest that the composite can be useful for drug delivery purposes.