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.
Keywords: Antimicrobial activity; Chitosan; Gold; Green synthesis; Hybrid nanoparticles.
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