Influence of tannic acid post-treatment on the degradation and drug release behavior of Schiff base crosslinked konjac glucomannan/chitosan hydrogel

Dynamic Schiff base-mediated natural polysaccharide hydrogels are often griped about rapid degradation as biological scaffolds, which is desirable for an efficient method to improve their stability. Herein, tannic acid (TA) was employed to further entangle Schiff base crosslinked hydrogel (CSGM) composed of carboxymethyl chitosan (CMCS) and oxidized konjac glucomannan (OKGM) to achieve tunable degradation and drug release of the obtained CSGM@TA hydrogel. As examined by SEM, the porous structure of CSGM hydrogel became denser after being immersed in TA solution, and the average pore size of CSGM hydrogel was decreased from 108.0 μm to 60.0 μm along with TA amount in CSGM@TA hydrogel. The degradation rate of CSGM hydrogel was remarkably inhibited upon entanglement by TA. CSGM@TA-3 with highest TA amount was found stable in PBS (pH 5.5) after 14 days, whereas ∼ 50 % of CSGM hydrogel was remained under same condition. The release of TA from CSGM@TA hydrogels was also examined under different pH, and the total TA release from three CSGM@TA hydrogels was 10 %–19 % within 14 days at pH 5.5, whereas the value was remarkably increased to 35 %–45 % at pH 7.4, suggesting a pH-dependent TA release behavior controlled by pH-responsive Shiff-base bonding and TA-CSGM bonding. Meanwhile, CSGM@TA hydrogels were found to possess good antioxidant, antibacterial, and anti-biofilm capabilities, demonstrating great potential as multifunctional scaffolds for tissue engineering and wound healing.