Tissue response to chitosan/γ-PGA polyelectrolyte complex using a rat model

In this study, the in vivo soft tissue response of chitosan/γ-poly(glutamic acid) (γ-PGA) polyelectrolyte complex (PEC) using a rat model was assessed using chitosan as a cationic polyelectrolyte and γ-PGA as an anionic polyelectrolyte; four groups of chitosan/γ-PGA PECs were synthesized according to the molar ratio of amine groups of chitosan to the carboxylic acid groups of γ-PGA. Different soft tissue responses to chitosan/γ-PGA PEC were observed between the epithelium and the muscle. In the epithelium, the wound dressed with chitosan/γ-PGA PEC healed faster than the control, with chitosan attracting polymorphonuclear (PMN) cells and γ-PGA creating a hydrophilic environment. In the muscle, a quantitative evaluation of the tissue response revealed that different degradation phenomena were evoked by different compositions of chitosan/γ-PGA PEC. After implantation for 28 days, the chitosan/γ-PGA PEC with chitosan dominating showed extensive surface erosion and superficial fragmentation surrounded by inflammatory cells, while chitosan/γ-PGA PECs with γ-PGA dominating elicited minimal degradation. These results confirm that the degradation of PECs can be controlled by tailoring the chitosan/γ-PGA PECs for different purposes. It appears that different local tissue conditions in muscle and epithelium may be involved in this difference.