Post grafted gallic acid to chitosan-Ag hybrid nanoparticles via free radical-induced grafting reactions.

The present study proposes two unique systems using free radical-induced grafting reactions to combine Ag, chitosan (CS) and gallic acid (GA) into a single particulate nanostructure. GA-grafted-CS (GA-g-CS) was used to reduce Ag+ to Ag0, and producing Ag-GA-g-CSNPs (hybrid NPs I). Also, GA was grafted into CS-AgNPs, to form GA-g-CS AgNPs (hybrid NPs II). Although there were previous attempts to graft GA into CS, this is first time to graft GA into CS-AgNPs. The study aimed to enhance biocompatibility, antibacterial and antioxidant properties of CS-AgNPs via grafted GA. Grafting GA into CS-AgNPs was confirmed by UV-Vis, DLS, DSC/TGA, XRD, EDX and FTIR. The morphology and size of NPs were studied by TEM and SEM. The decrease of ζ-potential from +50 mV in CS-Ag NPs to +33 and + 29 mV, in the presented 2 nanoforms hybrid NPs I and II, respectively, is an indication for the successful GA graft. Among all samples, hybrid NPs II showed lower toxicity, higher antioxidant and antibacterial activity. The obtained results revealed that grafting GA to CS-AgNPs, as a new method to combine Ag, CS and GA in a uniparticulate structure, is a unique process which may deserve a more future consideration.

Exploring the physicochemical and antimicrobial properties of gold-chitosan hybrid nanoparticles composed of varying chitosan amounts.

A green synthesis method for gold-chitosan hybrid nanoparticles (Au-CS hNPs) using different concentrations of CS as a capping/reducing agent is reported to investigate the effect of CS concentration on the physicochemical properties as well as the antimicrobial activity of the developed Au-CS hNPs. The as-synthesized Au-CS hNPs were characterized using visible spectrophotometry, FTIR, dynamic light scattering, DSC, XRD, SEM-EDX and TEM. The size of the formed hNPs ranges from 16.9 ± 3.9 nm (highest CS concentration) to 34.7 ± 7.6 nm (lowest CS concentration). It was noticed that increasing the amount of CS increases the ζ-potential from +25.1 to +53.1 mV and enhances the 6-months stability of the produced Au-CS hNPs. Furthermore, the obtained results indicated that the antimicrobial activity, in terms of MIC and CFU assays, is directly proportional to the amount of CS used in the preparation procedure. FTIR analysis revealed that the mechanism of formation of the Au-CS hNPs may involve complexation of CS with Au ions via its NH2 and OH groups followed by the chemical reduction of Au ions to metallic Au NPs. Eventually, higher amounts of CS are necessary for synthesizing highly stable Au-CS hNPs with small size, homogeneous shape and potent antibacterial/antifungal properties.