Abstract: In this study, a pH responsive carboxymethyl agarose-polydopamine (CMA-PDA) hydrogel carrier was developed. Carboxymethyl agarose (CMA) was synthesized by replacing the hydroxyl groups of agarose with chloroacetic acid and was characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and thermal gravimetric analysis (TGA). Then, the CMA-PDA hydrogel was prepared, and its rheological and texture properties were characterized. The results showed that the gel strength, hardness and viscoelasticity of the hydrogel were increased by the addition of PDA. Doxorubicin (DOX) was used as a model to study the release behavior of the hydrogel at pH 2.0, 6.2, 6.8 and 7.4. The results showed that the hydrogel had good pH responsiveness and the release rate was significantly higher at pH 2.0 than at other pH levels. Moreover, the hydrogel had no cytotoxicity on L929 cells. This study proves that CMA-PDA hydrogel has good biocompatibility, pH responsive and slow release properties, and can be used as a potential carrier for bioactive substance delivery.

Key words: carboxymethyl agarose; polydopamine; pH responsive; hydrogel; delivery carrier