Preparation of temperature-pH dual-responsive hydrogel from hydroxyethyl starch for drug delivery

A novel type of temperature-pH dual-responsive amphiphilic hydrogel, PD(hydroxyethyl starch(HES)-propynyl glycidylether(PGE)-2-dimethylamino ethanethiol (DMAET)-triethoxyvinylsilane (TEVS)) was synthesized and characterized. HES, a hydrophilic polysaccharide, underwent etherification of hydroxyl groups in its glucose units with PGE and then click reaction between carbon–carbon triple bonds in PGE and thiol groups in DMAET thereby possessing a hydrophilic-hydrophobic structure to be used for the preparation of PD, a temperature-pH dual-responsive material, with pH-responsive tertiary amine groups. Next, it further became a dual-responsive hydrogel through the formation of its internal network by TEVS. The hydrogel exhibited its maximum hydroswelling ratio of 2000 and a good transference between its shrinking and swelling. Moreover, during the test experiments to use it as a drug carrier for oral delivery, a doxorubicin (DOX) release was ≤ 15% in acidic conditions in the stomach (pH < 2.0) and ≤ 94% in basic conditions in the small intestine, ensuring that it exhibits relatively good protective and release properties of drugs.