Structure and interactions in chitosan hydrogels formed by complexation or aggregation for biomedical applications.

Area of Science:

• Biomaterials Science
• Polymer Chemistry
• Biomedical Engineering

Background:

• Covalently crosslinked chitosan hydrogels may have compromised biocompatibility.
• There is a need for alternative chitosan-based hydrogel systems for biomedical use.
• Physical hydrogels offer a promising approach by avoiding covalent crosslinkers.

Purpose of the Study:

• To review physical chitosan hydrogels and related networks for biomedical applications.
• To discuss the structural basis, formation principles, and physicochemical properties of these systems.
• To highlight alternatives to covalently crosslinked chitosan hydrogels.

Main Methods:

• Review of literature on physical chitosan hydrogels formed by aggregation or complexation.
• Analysis of network-forming interactions, formation principles, and physicochemical properties.
• Comparison of physical hydrogels (polyelectrolyte complexes, chitosan/PVA complexes, grafted chitosan hydrogels) with covalently crosslinked systems.

Main Results:

• Physical chitosan hydrogels are formed via polyelectrolyte complexation (PEC), chitosan/poly (vinyl alcohol) (PVA) complexation, or aggregation (grafted chitosan hydrogels).
• PEC exhibit enhanced pH-responsive swelling compared to covalently crosslinked hydrogels.
• Chitosan/PVA complexes are suitable for biocompatible drug delivery systems without strict pH-control requirements.
• Grafted chitosan hydrogels can improve intrinsic properties like bacteriostatic and wound-healing activity but are complex to prepare.

Conclusions:

• Physical chitosan hydrogels are viable alternatives to covalently crosslinked systems for biomedical applications.
• Complexation and aggregation offer tunable properties and improved biocompatibility.
• Further research into grafted chitosan hydrogels could enhance their therapeutic potential.