Structural Modulation of Chitosan/Polyacrylic Acid-based Hydrogels for Optimized Controlled Drug Release Performance

Graphical In this paper, the pH-responsive semi-interpenetrating CS/PAA hydrogel was synthesized through UV-initiated free-radical polymerization, enabling the incorporation of chitosan chains into the polyacrylic acid network. Moreover, adjusting the cross linking density of the polymer network and the content of pH-sensitive groups, such as amino and carboxyl groups, by modulating the CS/AA ratio can alter the swelling and pH sensitivity of hydrogels. The hydrogels exhibited not only a strong pH responsiveness, but also pH cycling reversibility, with reversible pH response for the sustained release of Asa in alternating cycles of pH 1.2 and 7.4. Hence, the hydrogels prepared in this study can be more suitable for use in the drug delivery through the human body system. A pH-sensitive semi-interpenetrating network hydrogel was synthesised by free radical polymerization using a one-pot method using chitosan (CS) and alanine (AA) as the raw materials, and then the hydrogel was immersed in a solution of the model drug aspirin (Asa) for loading, and subsequently used for drug sustained-release testing. The effects of the ratio of CS and AA on the internal structure of hydrogels were investigated, and the mechanism of CS/PAA semi-interpenetrating network hydrogels upon drug slow release was explored. The results showed that increasing the composite ratio of PAA resulted in a subsequent increase in the drug loading capacity of CS/PAA hydrogels and the cumulative release of drugs. When the concentration of the drug-loading solution was 200 mg/L, the drug loading and encapsulation efficiency of CS/PAA-1 were 16.23±0.57 (%) and 72.16±3.84 (%), respectively (p < 0.05). The hydrogels showed significant pH-responsive release properties and pH cycling reversibility, with 25.69±1.27 (%) and 77.21±2.68 (%) cumulative drug release over 24 h in the release media of pH 1.2 (simulating gastric fluid) and 7.4 (simulating intestinal fluid), respectively (p < 0.05), and the pH-responsive reversible release of Asa was maintained in alternating cycles in the release media with pH 1.2 and 7.4.