A short review on chitosan and gelatin-based hydrogel composite polymers for wound healing.

This review focuses on the modification of chitosan and gelatin-based hydrogel composite polymers for wound healing. First, the mechanical properties of several nanocomposite polymer hydrogels are compared based on water content, tensile strength, toughness and tensile strain. Furthermore, key findings on several modification techniques of the mechanical properties of chitosan are summarized. For example, we show that complexation of iron ions improves mechanical properties better than most other metal ions. Subsequently, gelatin - based hydrogel polymeric systems are compared on the basis of their preparative techniques, time to hemostasis, model and wound type, blood loss in treatment groups, biocompatibility and adhesive strength. Next, major outcomes on several techniques for improving the mechanical properties of gelatin biopolymer for wound healing are discussed. Then, effects of crosslinking on mechanical properties and hydrogel biocompatibility, in particular, the relationship between DHT crosslinking and gelation concentration are presented. Finally, research on adhesive anti-biofilm hydrogels are summarized, with focus on bacterial cellulosic, and chitosan - based hydrogels. Though similar reviews have been presented, the role of specific biological macromolecule-based composites such as chitosan and gelatin, have not been reviewed for some time despite the abundance of primary research findings. Knowledge gap and a list of unaddressed research questions are presented to aid further work in the field.