Covalent Chitosan-Cellulose Hydrogels via Schiff-Base Reaction Containing Macromolecular Microgels for pH-Sensitive Drug Delivery and Wound Dressing

Wound dressings with pH-sensitive properties, stable mechanical performance, and antibacterial properties have great potential for clinical applications. Herein, drug-loaded microgels via Schiff-base reaction between carboxymethyl chitosan and oxidized carboxymethyl cellulose are fabricated. Then they are embedded in hydrogels to form a hydrogel-microgels composite (Gel/MGs). The gelation time, morphologies, swelling ratio, weight loss ratio, mechanical properties, pH-sensitive drug release profiles, and antibacterial activities are examined. Adding microgels endows the hydrogels with more stable properties, enhanced mechanical performance, and drug release sensitivity to both acid and alkali in vitro. Gel/MGs dressings show a steady mass after 6 h and even maintain its 95.4% initial mass after 14 days in pH 7.4. In pH 9.5, Gel/MGs dressings also show a higher cumulative release of silver sulfadiazine than that in pH 7.4 and pH 5.5. Gel/MGs/AgSD dressings demonstrate desirable antibacterial properties, which may ensure their potential application in wound dressing.