Preparation Of Temperature Sensitive Adhesive Injectable Hydrogel Via Enzyme-mediated Cross-linking

In recent years,mussel-inspired adhesive hydrogel materials have become research hotspots in the research of polymer materials.Biomimetic mussel adhesive hydrogel has been extensively studied for the application in skin repair,tissue adhesion,wound healing and hemostasis due to its good biocompatibility,tissue adhesiveness,safety and non-toxicity.However,in most cases,the biomimetic mussel adhesive hydrogels were generally cross-linked by oxidizing agents such as sodium periodate?NaIO₄?,silver nitrate?AgNO₃?,etc.,or prepared by catechol-Fe³⁺coordination.There are some inherent shortcomings using oxidizing agents to form the biomimetic mussel adhesive hydrogels.On the one hand,insufficient oxidizing agent will reduce the gel strength,and on the other hand,excess oxidizing agent will reduce the biocompatibility of the material.Hydrogels prepared by catechol-Fe³⁺coordinated cross-linking method are generally not stable and weak gel strength.Horseradish peroxidase?HRP?can catalyze the oxidative cross-linking of the monohydric phenolic polymers in the presence of hydrogen peroxide?H₂O₂?,which is non-toxic,controllable,and highly efficient.However,this cross-linking method is rarely reported in the preparation of mussel-inspired adhesive hydrogels.In this thesis,HRP/H₂O₂ enzyme-catalyzed reaction was used to prepare a temperature-responsive mussel-inspired adhesive hydrogel.Then,the synthetic thermo-sensitive dopamine polymer and thiol-modified hyaluronic acid mixed solution was crosslinked in the presence of HRP/H₂O₂ to prepare injectable thermo-sensitive hyaluronic acid hydrogel.In the first part of the thesis,two kinds of temperature sensitive monomer2-?2-methoxy ethoxy?ethyl methacrylate?MEO₂MA?and oligo?ethylene glycol?methacrylate?OEGMA?and dopamine methacrylamide?DMA?were used to synthesis of temperature-sensitive dopamine-containing polymers through free radical polymerization.A series of temperature-sensitive adhesive hydrogels were prepared via enzymatic cross-linking.The experimental results showed that the hydrogel could quickly formed by enzymatically crosslinking method,and the gelation time could be tunable by adjusting the concentration of the polymer,HRP and H₂O₂.The swelling experiments and rheological tests showed that the hydrogel had an obvious temperature response.On the one hand,the equilibrium swelling rate of the hydrogel decreased significantly with increasing of temperature;on the other hand,mechanical strength of the hydrogel was enhanced over LCST.From the rheological tests,we can also draw a conclusion that the high content of catechol in the hydrogel does not contribute to the improvement of the mechanical strength.The results of self-healing,injectable and adhesion experiments showed that the thermo-sensitive adhesive hydrogel had the advantages of rapid self-healing,injectable and strong adhesion on different material surfaces.Adhesion performance of the hydrogel enhanced with increasing of temperature.In the second part of this thesis,HRP/H₂O₂ was added to the mixed solution of temperature-sensitive dopamine polymer and thiol-modified hyaluronic acid.The injectable temperature-responsive hyaluronic acid hydrogel was prepared by enzyme-catalyzed cross-linking.The temperature-response test showed that the temperature-responsive behavior of the hydrogel could be regulated by changing the HRP/H₂O₂ concentration.Rheological tests showed that the concentration ratio of HRP/H₂O₂ increased from 2.5 U·mL^-1/1.25 mM,5 U·m L^-1/2.5 mM to 10 U·mL^-1/5mM,and the storage modulus of the hydrogels increased from 365 Pa,407 Pa,to1084 Pa.Finally,swelling tests and drug release experiments showed that the gel had obvious temperature-responsive behavior.