| Hydrogels are a kind of three-dimensional polymer network,which can expand in water without dissolving.With certain mechanical properties,hydrogels also have deformation and softness,and good biocompatibility.Therefore,they have a wide range of applications in wound dressing,drug carrier,hydrogel soft robot,tissue engineering,and other fields.Polyethylene glycol（PEG）hydrogels are one of the synthetic hydrogels.They have a wide molecular weight range,no cytotoxicity,and low immunogenicity,so they have a good application prospect in the field of biomaterials.Chemical reaction crosslinking method is one of the commonly used methods to prepare PEG hydrogels.The PEG hydrogels prepared by this method have the advantages of good structural stability,simple operation,and easy regulation of the physical and chemical properties.In this thesis,PEG hydrogels with adjustable mechanical properties are prepared by the reaction of N,N’-thiocarbonyl diimidazole（TCDI）with amino group to form polythiourea.The PEG hydrogels have mild crosslinking conditions,good homogeneity,good biocompatibility,and can easily introduce various functionalized molecules containing amino functional groups.By introducing different functionalized molecules with amino groups and forming a double network structure with other physical cross-linked hydrogels,we also have regulated the mechanical properties,self-healing,stimuli-responsiveness properties of hydrogels,and studied the applications in shape memory hydrogels,hydrogels actuators,and three-dimensional cell culture.The thesis mainly includes the following three aspects:1.Polyethylene glycol（PEG）hydrogels are prepared by using 4-arm-polyethylene glycol-amine（4arm-PEG-NH2）as raw material and N,N’-thiocarbonyl diimidazole（TCDI）as crosslinking agent under the condition of 37℃.To discuss the effects of the gelling property or water absorption property of PEG hydrogel with different PEG content and proportion of crosslinking agent.The results show that the PEG hydrogels prepared with20%PEG content and 2:1 molar ratio of cross-linking agent to PEG have better stability and water absorption.2.Investigation of the stability and cytotoxicity of the PEG hydrogels cross-linked by glutaraldehyde（GA）or TCDI,and cell growth and proliferation with cell culture on the surface of PEG hydrogels.The results show that:（1）With the same PEG content,the PEG hydrogels cross-linked by TCDI have better stability and almost no cytotoxicity,while the PEG hydrogels cross-linked by GA have certain cytotoxicity.（2）Multicellular sphere can be obtain with cell culture on the surface of PEG hydrogels.3.Functionalized modification of PEG hydrogels.A method is to introduce functional molecules with amino,such as alkylamine with different carbon chain lengths,cystamine with redox responsive disulfide bond,and mesenchymal stem cells（MSCs）specific aptamer.To study the mechanical response of PEG hydrogels modified after modification and promote the differentiation of bone marrow mesenchymal stem cells（BMSCs）.To explore the mechanical properties,stimuli-responsiveness,and promotion of differentiation of bone marrow mesenchymal stem cells（BMSCs）of modified PEG hydrogels.Another method is to introduce physical cross-linked hydrogels network structures,such as gelatin and sodium alginate,to construct double network（DN）hydrogels with self-healing,stimuli-responsiveness,and shape memory function.The results show that:（1）With the increase of the content and the length of carbon chain of hydrophobic alkylamine,the mechanical properties of PEG hydrogels increase firstly and then decrease.（2）PEG hydrogels show redox responsiveness and degradability after introducing cysteamine.（3）Specific aptamer promotes BMSCs to differentiate into osteoblasts.（4）The PEG-Gelatin double network hydrogels have self-healing and temperature-responsive shape memory function,and the PEG-Sodium alginate double network hydrogels have ion-responsive shape memory function. |
