Preparation And Application Of A Hydrogel Containing Hydrazide Groups

Chitosan is a kind of natural polymer material with rich yield,excellent biocompatibility and cheap prise.In recent years,chitosan is being used more and more in hydrogels.In this paper,methyl acrylate was grafted on chitosan by Michael addition reaction.After hydrazine hydrolysis,acylhydrazine grafted chitosan?CS-N?was obtained,and then oxidized dextran was prepared by potassium iodate oxidation as macromolecular crosslinking agent to prepare CS-N/DEX-CHO crosslinking hydrogel.The effect of methyl acrylate dosage and reaction time on the substitution degree of methyl acrylate was discussed.According to the results,when the dosage of methyl acrylate is ten times equivalent of chitosan and the reaction time is 72 h,the ester-based chitosan with substitution degree of 0.867 can be obtained most efficiently.The C=O peak at 1726 cm^-1 after hydrazine hydrolysis was confirmed by infrared characterization,and the content of nitrogen in the product was characterized by Kjeldahl nitrogen determination method,which could prove that the ester group was hydrolyzed into hydrazide group by all hydrazine.Besides,the oxidation degree of dextran?DEX-CHO?under different dosage of potassium periodate was investigated.It was found that the oxidation degree of dextran increased with the increase of potassium periodate.The acylhydrazide group grafted on the molecular chain of modified chitosan?CS-N?and the amino group not involved in the reaction can cross-link with the aldehyde group on the oxidized dextran?DEX-CHO?to form the imine bond C=N..The chemical structure of hydrogel was characterized by infrared spectroscopy.It was found that the absorption peak at 1647 cm^-1 was added to the infrared spectrum of hydrogel,which was the characteristic peak of imine C=N,which indicated the successful crosslinking of CS-N/DEX-CHO hydrogel.The rheological properties,self-healing properties,swelling properties and drug release properties of the new hydrogel were investigated by rheological test,swelling test,scanning electron microscope and absorbance test.Then through the rheology test,swelling test,SEM,the rheological properties of the new hydrogel,self healing,swelling properties and drug release properties were explored.First,through rheological properties,The swelling ability and gel time explored the optimum crosslinking agent dosage and solid content of hydrogel.It turns out,when DEX-CHO/CS-N=1.5,hydrogels with a solid content of 15%can gell within 12 h,and its swelling rate was 545.439%,storage modulus?G'?=10040 pa.The complete and dense porous structure of hydrogel can be observed by scanning electron microscope.The hydrogel was then observed to be self-healing by a digital camera.In neutral conditions,the healing efficiency of aniline can reach 71%under the catalysis of aniline.Further investigate the effect of hydrazide substitution and p H value on self-healing properties of hydrogel using rheometer,It is found that hydrogels with different hydrazide substituents can be used in neutral conditions,healing under the catalysis of aniline,the healing efficiency was more than 70%.And in acidic conditions,the higher the degree of hydrazide substitution,the better the self-healing performance of hydrogel.Finally,the release ability of hydrogel was explored with BSA as model drug.The results showed that the hydrogel had a good sustained release effect and could release the embedded drug slowly through diffusion and Schiff bond degradation in acidic environment.Because the hydrazide bond is more stable than Schiff bond,the hydrogel with high hydrazide substitution degree has better stability and acid resistance under acidic conditions.In conclusion,it is found that this new CS-N/DEX-CHO hydrogel not only has good self-healing function,but also has drug slow release ability.Furthermore,the range of p H values and the ability to release drugs can be changed by changing the substitution degree of hydrazide to adapt to different needs and various complex environments.Based on the above characteristics,this new hydrogel has shown a good application prospect in the field of biomedicine and tissue engineering.