Preparation Of Dextran-based Hydrogel

Dextran is widely used in the field of hydrogels as a commonly used biological macromolecular material.However,the main chain of dextran is hydroxyl,so its reactivity is not high,and modification is difficult.Therefore,in order to improve its practicality in application,it is given certain intelligent responsiveness.In this paper,we tried to introduce carboxyl groups into dextran,which not only retained the biocompatibility of dextran but also improved its solubility,which provided the possibility for the subsequent reaction.In this experiment,dichloroacetic acid was used as a carboxylating agent to introduce carboxyl groups into dextran,and carboxymethyl dextran was successfully prepared.In the preparation process of carboxymethyl dextran,the factors affecting the degree of substitution of carboxymethyl dextran were explored by changing the concentration of NaOH,the amount of carboxylating agent,the temperature of the reaction and the reaction time.The results showed that when the concentration of NaOH was 50%,the amount of dichloroacetic acid was 15ml,the reaction temperature was 60?,and the reaction time was 5h,the carboxymethyl dextran with a high degree of substitution was prepared.By oxidizing thioglycerol to form a disulfide bond and using it as a cross-linking agent,carboxymethyl dextran and pectin were cross-linked together to form a macromolecular hydrogel.The physical and chemical properties of hydrogels containing disulfide bonds were characterized by Fourier infrared spectroscopy,Raman spectroscopy,scanning electron microscopy,rheological testing,swelling performance testing,drug release behavior and the degradation performance.Comprehensive infrared and Raman analysis results found that the sulfhydryl infrared absorption peak of the oxidized thioglycerol disappeared,and the characteristic peak of the disulfide bond can be detected at about 500 cm^-11 in the Raman spectrum,indicated that the disulfide bond was successfully prepared.The infrared spectrum of the hydrogel showed a peak of ester groups at 1723.69 cm^-1,indicated that the hydrogel was successfully prepared.In addition,the influence of the content of the cross-linking agent on the swelling and rheological properties of the hydrogel was also explored.The results showed that when the content of the cross-linking agent was 30%,the swelling of the hydrogel reached 233.1135%.And through scanning electron microscopy,we can observed that the hydrogel has a very good network structure.In order to explore the drug-carrying capacity of hydrogels,BSA was used as a drug model to carry out drug-carrying tests on hydrogels.The test results were calculated to show that the drug loading of hydrogels was 5.73%and the encapsulation rate of hydrogels was 32.63%.Since the disulfide bond is a covalent bond with reversible properties,the disulfide bond can be formed by oxidation of the sulfhydryl group,and conversely,the disulfide bond can be broken to generate two sulfhydryl groups in a certain reducing environment.Based on this theory,we conducted a reduction responsiveness test on the hydrogel with DTT as the reducing agent,so that the hydrogel undergoes a reduction reaction in the solution containing DTT and breaks to generate two thiol groups,at which time the hydrogel degrades.The degradation behavior of the hydrogel further showed that the disulfide bonds were well cross-linked in the hydrogel.In summary,the hydrogels containing disulfide bonds not only have a certain drug loading and drug release capacity,but also can control the degree of drug release of hydrogels by regulating the reductive cleavage of disulfide bonds,thus giving dextran hydrogel has certain intelligent responsive drug-loading and drug-releasing capabilities,which makes it have certain application value in the field of biomedicine.