Preparation of pH-responsive SA/OHA hydrogels and its curcumin drug release properties

In this paper, smart hydrogels (SA/OHA) with pH-responsive properties were successfully prepared by using sodium alginate (SA) and oxidized humic acid (OHA) as raw materials and CaCl₂ as cross-linking agent. By means of FTIR, XRD and SEM tests, it was shown that the three-dimensional network structure gel spheres with good gelation state were formed by physical and chemical cross-linking between SA and OHA and Ca²⁺ to form a pore structure in the range of 50–500 μm. The rate of gelation, drying rate, pH sensitivity, antimicrobial and degradation properties of the SA/OHA hydrogels were better than those of the SA hydrogels, and the kinetic study of the swelling showed that the swelling process followed Schotts’ second-order kinetic model. The drug loading rates of SA-loaded hydrogel and SA/OHA-loaded hydrogel were 49.36 mg/g and 62.45 mg/g, respectively, and the encapsulation rates were 45.28% and 59.36%, respectively. The maximum Cur release of SA carrier gel in pH 1.4 and pH 7.4 buffer solutions was 30.14% and 72.99%, respectively. The maximum emission of SA/OHA liquid carrier gel to Cur was 18.77% and 91.56% in pH = 1.4 and pH = 7.4 buffer solutions, respectively. The release of SA/OHA gel to Cur conforms to the Higuchi kinetic model and has good drug slow-release properties and pH sensitivity.