Injectable and Self-Healing Chitosan Hydrogel Based on Imine Bonds: Design and Therapeutic Applications.

Biological tissues can automatically repair themselves after damage. Examples include skin, muscle, soft tissue, etc. Inspired by these living tissues, numerous self-healing hydrogels have been developed recently. Chitosan-based self-healing hydrogels constructed via dynamic imine bonds have been widely studied due to their simple preparation, good biocompatibility, and automatic reparability under physiological conditions. In this mini-review, we highlighted chitosan-based self-healing hydrogels based on dynamic imine chemistry, and provided an overview of the preparation of these hydrogels and their bioapplications in cell therapy, tumor therapy, and wound healing.

Controlled release of ionic drugs from complex micelles with charged channels.

Oral administration of ionic drugs generally encounters with significant fluctuation in plasma concentration due to the large variation of pH value in the gastrointestinal tract and the pH-dependent solubility of ionic drugs. Polymeric complex micelles with charged channels on the surface provided us with an effective way to reduce the difference in the drug release rate upon change in pH value. The complex micelles were prepared by self-assembly of PCL-b-PAsp and PCL-b-PNIPAM in water at room temperature with PCL as the core and PAsp/PNIPAM as the mixed shell. With an increase in temperature, PNIPAM collapsed and enclosed the PCL core, while PAsp penetrated through the PNIPAM shell, leading to the formation of negatively charged PAsp channels on the micelle surface. Release behavior of ionic drugs from the complex micelles was remarkably different from that of usual core-shell micelles where diffusion and solubility of drugs played a key role. Specifically, it was mainly dependent on the conformation of the PAsp chains and the electrostatic interaction between PAsp and drugs, which could partially counteract the influence of pH-dependent diffusion and solubility of drugs. As a result, the variation of drug release rate with pH value was suppressed, which was favorable for acquiring relatively steady plasma drug concentration.