Tracking the enzyme-response mechanism of tannic acid-embedded chitosan/γ-polyglutamic acid hydrogel

The design of enzyme-response hydrogels has attracted increasing interest in cell therapy, biomedical research, and tissue engineering. Their rational design usually depends on the enzyme-response mechanism and have focused on behavior improvement, drug delivery, and state transition of hydrogels. However, no enzyme-response mechanism has yet been systematically investigated. Here, we construct a tunable platform of tannic acid-embedded chitosan/γ-polyglutamic acid hydrogel to study the enzyme-response mechanism. We track the roles of gallic acid hydrolyzed from tannic acid in altering the structure and properties of the hydrogel to get insights into the mechanism. The gallic acid inside the hydrogel enhances hydrogel crosslinking, increasing the mechanical properties and pH sensitivity but reducing thickness, porosity, and swelling behavior. The gallic acid outside the hydrogel increases the positive potential and superficial hydrophobicity of the hydrogel. These findings will aid the rational design of other enzyme-response hydrogels in more extensive self-adaptive fields. Understanding enzyme-response mechanisms is important for designing materials in cell therapy, biomedical research, and tissue engineering. Here, a chitosan/γ-polyglutamic acid hydrogel is designed as a platform to understand the role of gallic acid in the enzyme-response mechanism.