Hydrogel nanocomposites based on chitosan-g-polyacrylamide and silver nanoparticles synthesized using Curcuma longa for antibacterial applications

Hydrogel nanocomposites based on chitosan-g-polyacrylamide and silver nanoparticles (Cs-g-PAAm/AgNPs) were developed by simple, cost effective, and eco-friendly process at room temperature. First, the hydrogels were prepared via grafting copolymerization and crosslinking of acrylamide (AAm) onto chitosan (Cs) with various weight ratios, using potassium persulfate as initiator and N,N′-methylenebisacrylamide as crosslinker, and then hydrolyzed to achieve materials with uppermost swelling properties. Finally, the AgNPs were biosynthesized and entrapped into hydrogels as templates using aqueous silver nitrate as precursor and Curcuma longa tuber extract as both reducing and stabilizing agents. The influences of the templates and the silver precursor concentrations on the AgNP formation and the properties of the elaborated nanocomposites were investigated. The UV–visible spectroscopy has confirmed the occurrence of the nanosilver particle formation, while the X-ray diffraction analysis has evidenced their face-centered cubic crystalline phase. The inductively coupled plasma analysis has revealed that the extent of AgNPs into the network increases by a decrease in Cs weight ratios and an increase in AgNO3 concentrations. Transmission electron microscope images have showed a spherical shape of AgNPs with average sizes <26 nm. Interactions between hydrogel functional groups and those of proteins extracted from C. longa, which are probably the capping ligands of the AgNPs, were suggested from Fourier transform-infrared spectroscopy. Slight enhance in thermal stability of nanocomposites was noticed from thermogravimetric analysis. Besides, the swelling and retention capacities were affected by both Cs and AgNP contents. Furthermore, the swelling kinetics was found to obey the second-order model with non-Fickian diffusion. The antibacterial activity against Staphylococcus aureus and Escherichia coli bacteria was examined by both zone inhibition and dynamic shake flask methods and the results have showed an efficient activity of AgNP-loaded hydrogels with a maximum of killing ratio of 99.99%. Finally, it is suggested that the optimized hydrogel nanomaterials can be candidates for bio-applications.