Synthesis of pH-, thermo- and salt-responsive hydrogels containing MCM-41 as crosslinker in situ for controlled drug release

Stimuli-responsive hydrogels are attracting extensive attention in drug delivery system. Here, a novel pH, thermo and salt sensitivity of composite hydrogels was synthesized in situ from polysuccinimide modified by γ-aminopropyltriethoxysilane with mesoporous molecular sieves (MCM-41) as only crosslinking agent for controlled salicylic acid release. Morphologies and thermal behaviors of KPAsp/MCM-41 hydrogels were characterized by scanning electron microscopy and thermogravimetric analysis. Swelling dynamic behaviors, pH, thermo and salt sensitivities and drug releasing capacities of composite hydrogels were also systematically investigated. The obtained results show that multi-responsive hydrogels are very sensitive to environmental pH, external temperature and ionic valence, which indicated that the MCM-41 addition not only can ameliorate the network structure, but also can enhance the drug loading and releasing capacity. The controlled salicylic acid release rates of MCM-41/KPAsp hydrogels can reach to 33.6% and 61.2% in simulated gastric fluid (pH = 1.2) and in simulated intestinal fluid at (pH = 7.4) at 37 °C, respectively. The as-synthesized multi-responsive hydrogels reported here are promising candidates for application in targeted drug delivery system.