Synthesis And Application Of Intelligent Supramolecular Hydrogels Including Cytosine-guanine Base-pairings

In 1953,James Watson and Francis Crick proposed the double helix structure of DNA,they found that the bridging hydrogen bonds between the complementary base pairs A-T(adenine-thymine)and G-C(guanine-cytosine)form the DNA structure.The highly accurate and directional base pairs have been brought into the field of supramolecular chemistry.Although base pairs have played an important role insupramolecularchemistry,the application in biomedical polymers is still in its infancy.On the other hand,the mechanical properties of traditional PEG/?-CD supramolecular hydrogels still have a needto be improved.In this thesis,PEG/?-CD based hydrogelswith good biocompatibility were used for combiningwith C-G base pairs.The introduction of C-G base pairs significantly increased the number of the crosslinks and increased the crosslink density,resulting in stronger mechanical properties of the hydrogels.On the above premise,intelligent supramolecular hydrogels was prepared by the introductionof stimulating functional groups.This thesis mainly includes the following two parts:1.For the preparation of temperature sensitive supramolecular hydrogels,cytosine(C)/ guanine(G)base pairs were introduced into the construction of PEG/?-CD hydrogels.The results show that the introduction of base pairs improves the crosslink density and the mechanical properties of hydrogels.Further,we discussed the feasibility of supramolecular hydrogels as drug carriers,the in vitro drug release experiment showed that the base pairs containing supramolecular hydrogels(SHG)havegood DOX sustained-release behavior.In vitro cytotoxicity tests also proved the excellent biocompatibility and biomedical application prospect of SHG hydrogels.2.On the basis of the first part of this thesis,we used guanine modified reactive oxygen species(ROS)sensitive thioketal linker(G-TK-G)for connectingthe cytosine modified PEG(C-PEG-C),prepared ROS sensitive hydrogels(TKHG).The ROS sensitivity of intelligent TKHG hydrogels was evaluated,and the DOX loading and release of TKHG hydrogels were investigated.The results show that the prepared TKHG has enhanced mechanical properties and good ROS responsive DOX release behavior.