Preparation And Characterization Of Thermal/PH-responsive And Injectable Hydrogel Based On Amino Acid

Series of thermal-and pH-responsive polymers based on glutamate derivatives were synthesized.The effects of temperature and pH on the properities of the copolypeptides solution were investigated.The dissertation includes the following sections.1.We reported a facile and efficient approach to prepare a class of dual-responsive statistical/block copoly(L-glutamate)s by ring-opening polymerization(ROP)and post-modification strategy.Both the oligo(ethylene glycol)(OEG)and glutamic acid residues were incorporated to offer thermaland pH-responsive property simultaneously.We present a systematic study of the influence of both temperature and pH on the solution properties of the copolypeptides.The copolypeptides show entirely reversible pH-dependent thermal-responsive behaviors with tunable phase transition temperatures.The α-helix conformation appears to be the dominant secondary conformation,which shows the pH dependence,but generally irrespective of the temperature.We further verify that the reduced CD signal upon heating above the clouding point(CP)is entirely due to the aggregation of the polymer chains.More interestingly,we show that the solution behavior of block copolypeptide is less dependent on pH.All these features make the obtained polypeptides potential candidates for next generation of smart protein-mimetic materials.2.We reported a facile approach to prepare a class of dual-responsive hydrogels assembled from synthetic statistical/block thermal-responsive copoly(L-glutamate)s copolymerized with poly(ethylene glycol),which were prepared by ring-opening polymerization(ROP)and post-modification strategy.The incorporation of oligo(ethylene glycol)(OEG)and glutamic acid residues offers thermal-and pH-responsive property simultaneously.We present a systematic study of the influence of both temperature and p H on the gelation behavior of the block copolymers.Phase diagrams of the hydrogels at different concentrations are shown.Both the increased DP of PGA untis and pH value can suppress the gelation ability of the samples.CD results show that the α-helix conformation appears to be the dominant secondary conformation.More interestingly,the gelation property of the diblock copolymer PEG-b-Poly[(PLG-g-EG)-b-GA] shows greater dependence on pH as compared to triblock copolymer PEG-b-(PPLG-g-EG)-b-PGA,may due to the distinct morphology of the self-assemblies.The obtained hydrogels exhibit pH-dependent thermal-responsive gelation behavior that enables them become an ideal material for biomedical applications.