Boosting the antibacterial activity of chitosan–gold nanoparticles against antibiotic–resistant bacteria by Punicagranatum L. extract

[Display omitted] •Pomegranate extract as a capping agent for gold-chitosan hybrid nanoparticles.•Activity against antibiotic-resistant Staphylococcus aureus.•Pomegranate extract enhances the characteristics of the hybrid nanoparticles.•Long shelf-life stability of the carbohydrate polymer-containing nanoparticles. The present work describes the synthesis of a new series of chitosan–gold hybrid nanoparticles (CS–AuNPs) for the delivery of Punicagranatum L. extract (PE). It proposes CS and PE as reducing agents for gold ions in aqueous solution. The effect of PE on the physicochemical properties of the CS–AuNPs was investigated with UV spectroscopy, DLS, DSC, XRD, FTIR, SEM/EDX and TEM. Interestingly, about 50 % reduction in size was observed with using PE alone for gold reduction. The ζ–potential of CS–AuNPs was shifted from +53.1 ± 6.7 mV to 31.0 ± 6.0 mV upon conjugation of the negatively–charged PE polyphenols. The developed PE–conjugated CS–AuNPs exhibited higher stability at different pH values. About 87 % of the loaded PE was released from the NPs over 24 h. The antibacterial activity of CS–PE–AuNPs displayed a synergetic affect against methicillin–resistant S. aureus with MIC and MBC values of 15.6 and 62.5 μg/mL, respectively.