Dual responsive antibacterial Ag-poly(N-isopropylacrylamide/itaconic acid) hydrogel nanocomposites synthesized by gamma irradiation

Abstract

Thermo- and pH-sensitive Ag-P(NiPAAm/IA) hydrogel nanocomposites were prepared by in situ reduction of Ag+ ions with gamma irradiation. P(NiPAAm/IA) copolymer hydrogel matrices have been previously synthesized by radiation induced copolymerization. The copolymer composition was determined by elemental analysis of the dried gels, and was found to be close to that of the feed. The dependence of swelling properties and phase transitions on the IA comonomer content, temperature, pH values and presence of AgNPs were investigated. The hydrogels showed both thermo- and pH responses. By introducing small amounts of IA, swelling capacity increase, and the volume phase transition temperature (VPIT) of P(NiPAAm/IA) copolymers is transferred to higher values. Presence of AgNPs causes decrease of equilibrium swelling degree and VPIT, and allows of fine-tuning of these properties. Both the average values of compressive elastic modulus and Young's modulus of elasticity were decreased by addition of IA as a consequence of looser structure of the network (increase in molar mass between two neighboring crosslinks and decrease in effective crosslinking density). The introduction of AgNPs promoted not only improvement of these mechanical parameters, but an improvement of stress at failure especially in the systems with the highest content of IA. In addition, Ag-P(NiPAAm/IA) hydrogel nanocomposites showed good antibacterial potentials.