Tris(2-(2-formylphenoxy)ethyl)amine was designed and synthesized by reaction of salicylaldehyde with tris(2- chloroethyl)amine hydrochloride and evaluated as a new multi-functional cross-linker for preparation of new pH- and thermo-responsive chitosan hydrogels through formation of covalent Schiff-base linkage. The structure and properties of the hydrogels were characterized by FT-IR, 1H NMR and scanning electron microscopy (SEM). The swelling behavior of prepared hydrogels at different pHs and temperatures was investigated. Also, in vitro controlled release behavior of the metronidazole model drug was studied with prepared hydrogels. The release profiles of metronidazole from the hydrogels were determined by UV–Vis absorption measurement. The results showed that the new hydrogels exhibit a pH and temperature-responsive swelling ratio. Also, the pH and temperature were found to strongly influence the drug release behavior of these swollen polymers. Due to the concurrent rapid and significant stimuli-response, these smart hydrogels prepared from chitosan as a natural polymer may expand the scope of hydrogel applications in various fields of research such as targeted (cellular or tissue) delivery of drugs. In addition, these new hydrogels can be used to improve bioavailability, sustain release of drugs or solubilize drugs for systemic delivery.
