?-Alanine enhancing the crosslink of chitosan/poly-(?-glutamic acid) hydrogel for a potential alkaline-adapted wound dressing

Tiny crosslink in chitosan (CS)/poly-(gamma-glutamic acid) (gamma-PGA) hydrogel leads to some disadvantages including low mechanical strength and high swelling. To enhance the crosslink of CS/gamma-PGA hydrogel, amino acid (AA) was introduced to remove the drawbacks. The results indicated that AA can dramatically increase the crosslink and mechanical properties of CS/gamma-PGA hydrogel, and AA chain length and concentration have a drastic effect on them. Particularly, 0.5 % beta-Alanine (beta-Ala) decreased the hydrogel by 70 % in porosity, 52 % in water solubility, and 30 % in swelling, but increased by 2.2-fold in elastic modulus, 2.08-fold in stress, and 1.53-fold in water retention. The porosity of the hydrogel correlates positively with the elastic modulus but negatively with the crosslinking degree. The effect of pH on CS/beta-Ala/gamma-PGA hydrogel was investigated in the load and release of benzalkonium chlorides (BAC). beta-Ala strengthened pH response of the hydrogel in BAC load and release. The loading capacity increased with pH value, and 0.5 % beta-Ala increased the hydrogel by 1.25-fold in the release capacity in alkaline environment, suggesting a good buffering effect of beta-Ala on pH variation to accelerate the transportation of BAC. CS/beta-Ala/gamma-PGA hydrogel will be competently applied as a potential material for wound dressing in alkaline environment.