Study On Synthesis And Application Of Gelatin/N-isopropyl Acrylamide Hydrogels

Temperature sensitive hydrogels have a wide potential application in the biomedical field,because of its unique responsiveness to environment,and have received more attentions of scholars at home and abroad.Poly（N-isopropylacrylamide）（PNIPAM）hydrogels,as a typical temperature sensitive hydrogel,undergo phase transition at the low critical phase transition temperature（LCST,about 32 ℃）,which is close to the human physiological environment temperature,so the PNIPAM have been the most studied.Gelatin,as a natural polymer,has good biocompatibility and low cytotoxicity,and its side chains contains a large number of active functional groups,which can be modified to improve its application potential.In this study,NIPAM and gelatin were used as the natural materials to prepare temperature sensitive hydrogels.The main research works of this paper were as follows:1.Poly（N-isopropyl acrylamide-co-acylated gelatin）hydrogels were successfully prepared.Firstly,the gelatin was grafted with methacrylic anhydride（MA）,and the acylated gelatin（GelMA）was obtained.The grafting degree of gelatin was characterized by using the method of ninhydrin assay,and the grafting degree was about 89.9%.Poly（GelMA-NIPAM）（GN）hydrogels were prepared by copolymerization of NIPAM with GeIMA,by using ammonium persulfate（APS）as thermal initiator.The FT-IR spectra verified the formation of thermosensitive GN hydrogels.2.The effects of GelMA contents on the structure of GN hydrogels were studied.In first,DSC curves of dried GN hydrogels samples revealed that GN hydrogels have comb structures,with GelMA as the main chains and the PNIPAM as the side chains,by comparing the differences of Tgs.With the increasing of GelMA contents,the grafting density decreased,the meshs became larger and the distributions became broader.The microstructure of GN hydrogels were observed by SEM,and we also calculated the porosity of GN hydrogels.The results confirmed the previous conjecture.3.The temperature sensitivities of GN hydrogels were studied.The GN hydrogels aqueous solutions were tested by DSC,and the temperature sensitivity of GN hydrogels were analyzed according to points of the melting peak(T_DSC,peak)of DSC curves.The results demonstrated that with the increasing of GelMA contents,the LCST of GN hydrogels decreased.The DSC curve of GN-5 hydrogel was a cyclic closed coil,which indicates that the temperature sensitivity of GN-5 hydrogel was reversible.4.The application of GN hydrogels in drug release field were explored.In this study,ibuprofen was used as a model drug.It was noticed that with the increasing of GelMA amounts,the release rate of ibuprofen became faster,and the amount of release rate was more,which was up to 83.7%within 12 h.And the results of drug release were in keeping with the analysis results of the microstructure.5.The effects of gelatin contents on the LCSTs of GN hydrogels were studied.It was found that the LCST decreased when the ratio of gelatin/GN was 2:3.And when gelatin was added,the GN hydrogels exhibited the phenomenon of delamination and swelling property.