Citric Acid Cross-Linking of Carboxymethyl Sago Starch Based Hydrogel for Controlled Release Application

Carboxymethyl sago starch (CMSS) is prepared using carboxymethylation reaction. The reaction times are varied to determine the optimum degree of substitution (DS) and reaction efficiency (RE). The CMSS prepared via carboxymethylation for 3 h shows the highest DS and RE. The CMSS hydrogel is prepared using citric acid as a cross-linker. The effects of the preparation condition of citric acid/CMSS hydrogel such as the percentage of citric acid (w/w), cross-linking periods, and cross-linking temperature on the gel fraction are investigated. The optimization of preparation conditions of hydrogels using cross-linker demonstrated 25% higher gel fraction compared to previously reported sago starch hydrogels prepared via irradiation cross-linking. The swelling study is carried out in distilled water (pH 6.5), acidic (pH 1.2), neutral (pH 7.4), and alkaline (pH 11) media. The release behavior of methylene blue (MB) as the drug model suggests the potential of CMSS hydrogel to be used in drug delivery applications.