Ag/Au-incorporated trimethyl chitosan-shell hybrid particles as reinforcing and antioxidant fillers for trimethyl chitosan hydrogel.

N,N,N-Trimethyl chitosan (TMC) is a quaternized chitosan with versatile biological features. However, low mechanical strength limits its uses, for example, as hydrogels for tissue engineering applications. This study illustrates a viable synthesis of metal/polymer hybrid, core-shell colloidal particles and their use as reinforcing and antioxidant fillers for TMC hydrogels. The core-shell particles were initially synthesized by surfactant-free emulsion polymerization, induced by a photo-redox initiating system of riboflavin assisted by a 3° amine and 2° alcohol co-initiators. The synthesized core-shell particles were based on two polymeric shells: TMC and chitosan, and two polymeric cores: poly (hydroxypropyl methacrylate) (PHPMA) and poly(2-hydroxy ethyl methacrylate) (PHEMA). The presence of both 3° amine on TMC and 2° alcohol on HPMA monomer enhanced the photopolymerization performance. The TMC-based particles had sizes of 122-154 nm and zeta potentials of 10-35 mV, bringing the colloidal stability in the 4-10 pH range. Furthermore, due to the presence of TMC on the shell layer, the core-shell particles could be used as templates to grow the Ag/Au bimetallic nanoparticles with alloy and core-shell types through a thermal reduction. The prepared hybrid particles were incorporated in TMC hydrogels as a multifunctional filler, improving their mechanical and antioxidant properties.