Study Of Gelatin-based Antibacterial And Adhesive Composite Hydrogels

As a highly hydrophilic polymer material with three-dimensional network,hydrogel has a broad application prospect in biomedical fields such as tissue repairing.The internal structure similar to the natural tissues endows it with high biomimetic properties and good biocompatibility.When hydrogel is used as an implantable repair material,bacterial infection is usually easily caused in the wound in surgical operation,which increases the tissue morbidity and prolongs the wound healing process,and finally leads to the failure of implantation.Therefore,it has always been a challenge to develop a hydrogel with rapid gelation properties,excellent tissue adhesion,good mechanical properties and inherent antibacterial properties.The main idea of the work is to prepare gelatin-based hydrogels with natural polymers as matrix materials through simple chemical cross-linking,and to prepare a series of adhesive hydrogels and antibacterial hydrogels with rapid gelation through further structural design and regulation.The specific research contents are as follows:(1)The oxidized konjac glucomannan(OKG)was prepared by the oxidation of konjac glucomannan(KGM)with sodium periodate.The effects of preparation conditions on the aldehyde group content of OKG was studied,with the preparation parameters optimized.Using the OKG prepared under the optimal conditions as a chemical crosslinking agent,gelatin-based composite hydrogels were prepared by the Schiff base reaction between gelatin and OKG.The effects of OKG dosage on the mechanical properties,cross-linking degree and swelling property of gelatin-based hydrogels were studied,and the cytotoxicity of gelatin-based hydrogels was further evaluated.The results showed that with the increase of the OKG from 1.0%(w/v)to5.0%(w/v),the cross-linking degree of hydrogel was increased from 12.13% to 57.72%,and a gradually decreasing was found in the equilibrium swelling rate.At the OKG concentration of 2.0%(w/v),the maximum compression stress reached 0.68 MPa,34 times higher than that of pure gelatin hydrogel.The results of cell experiments showed that both G-OKG2 and G-OKG5 hydrogels could support the proliferation and growth of cells,indicating a good biocompatibility.(2)The effect of the molecular weight of OKG on the structure and properties of gelatin-based hydrogels was studied with infrared spectroscopy,scanning electron microscopy,rheology,mechanical and biocompatibility tests.The results showed that with the increase of molecular weight of OKG,the degree of entangling between gelatin chain and polysaccharide chain increased,and both high mechanical strength and good self-healing ability were achieved for the composite hydrogels.In addition,the prepared hydrogels can support the proliferation of cells,suggesting a good application prospect in biomedical fields.(3)Based on the above works,the catechol derivative dopamine(DA)was further introduced to prepare a mussel-inspired adhesive hydrogel with rapid gelation.The effects of DA on the properties of gelatin-based hydrogels were studied.The gelation mechanism,gelation time,internal morphology,mechanical properties,adhesion,swelling and degradation,and self-healing of hydrogels in different groups were analyzed.The cytotoxicity of hydrogels was evaluated by cell experiments.The results showed that besides the Schiff base reaction,the self-polymerization of DA takes place in G-OKG-DA hydrogel.The introduction of DA makes the hydrogel to be quickly gelatinized,improves the mechanical properties,and tights the internal morphology.The G-OKG-DA hydrogel has good adhesion to porcine skin tissues,with an adhesion strength of 150.07 k Pa,18 times of the commercially available fibrin glue.In addition,cell experiment results showed that compared with G-OKG hydrogels,G-DA and GOKG-DA hydrogels are more conducive to cell adhesion and proliferation,suggesting potential application for biomedical tissue repairing.(4)The modified gelatin with hydrophobic alkyl chain was prepared by grafting lauraldehyde onto the gelatin chain,and the antibacterial adhesion hydrogels based on hydrophobic modified gelatin were synthesized.The effects of hydrophobic modified gelatin and different degrees of hydrophobic modification on the gelation time,internal morphology,mechanical properties,swelling and degradation properties and adhesion properties of hydrogels were studied.The antibacterial activity of hydrogels against E.coli and S.aureus were investigated through antibacterial experiments.The results showed that the hydrophobic modified gelatin could promote the gelation of hydrogels.With the increase of hydrophobic modification degree of gelatin,the compression strength and compression modulus of the composite hydrogels showed an opposite trend.The results of tensile-shear test showed that the adhesion ability of hydrogels to porcine skin decreased with the increase of hydrophobic modification degree.The composite hydrogels prepared by hydrophobic modified gelatin is good in antibacterial activity against S.aureus and E.coli.