Synthesis of casein-γ-polyglutamic acid hydrogels by microbial transglutaminase-mediated gelation for controlled release of drugs

Casein-based hydrogels were reported as biodegradability, biocompatibility, and non-toxic materials that had potential in drug delivery. At present, we prepared two kinds of casein/γ-PGA hybrid hydrogels, 1/5 and 1/9, based on the ratio of γ-PGA to casein. The hydrogels were crosslinked by microbial transglutaminase (MTG), the physicochemical properties of the casein/γ-PGA hydrogels were investigated by scanning electron microscopy (SEM) observation, differential scanning calorimetry (DSC) analysis, texture analysis, swelling ratio test, and stability test. The hydrogels showed a well-interconnected sparse and porous structure. The 1/5 casein/γ-PGA hydrogel was much stable, hard, and cohesive than the 1/9 casein/γ-PGA hydrogel, and the 1/5 casein/γ-PGA hydrogel showed a higher swelling ratio and lower degradation rate. To investigate in vitro release behavior, we chose the hydrophilic vitamin B12 and hydrophobic aspirin as the model drugs incorporated into the casein/γ-PGA hydrogels. The 1/5 casein/γ-PGA hydrogel exhibited a good drug release behavior.