Study On Preparation And Properties Of Sericin Hydrogel

Sericin is a kind of natural protein secreted by Bombyx mori.It not only has the characteristics of moisturizing,anti-inflammatory,antioxidant,high biocompatibility,and no immunity but also has abundant active groups that are easy to modify.It is an excellent material for preparing biomedical hydrogels.In recent years,a variety of sericin hydrogels have been prepared.They have been used as delivery carriers for drugs or growth factors,cell scaffolds,and the repair of various tissue injuries.However,there are still some problems in the existing sericin hydrogels,such as poor mechanical strength,non-sterility,and low transparency.In this study,two new pure sericin hydrogels were prepared by sericin extracted from cocoons or silkworm bodies of the fibroin-deficient silkworms.The physicochemical properties and cytocompatibility were systematically characterized.The aim of this study is to solve the deficiency of sericin hydrogels and expand the application of sericin hydrogels in tissue engineering.1.Preparation and performance study of sterile and injectable sericin hydrogel with high mechanical propertiesIn this part,silk fibroin-deficient mutant silkworm(180 Nd-s)cocoons were selected,washed,and ground into powder.The sterile sericin solution with high concentration and free amino content could be obtained after high temperature and high pressure(121℃,0.1MPa)treatment.Then sericin solution was crosslinked with genipine to prepare sterile and injectable sericin hydrogel with high mechanical properties.The gelation time can be controlled by adjusting the concentration of sericin solution,which ranges from ten minutes to several hours.In terms of microstructure,the pore sizes of sericin hydrogel scaffolds with different concentrations ranged from 4.9-7.1 μm,and the porosity ranged from 66%-79%.The adjustable pore sizes could be used for different cell cultures and tissue repair.The sericin hydrogel also has excellent swelling and degradability.Both swelling and degradation are pH responsive.It had a maximum swelling rate of 800% under alkaline conditions(pH 11.0).In terms of degradability,the degradation rate of sericin hydrogel was the fastest under alkaline conditions(pH 11.0),followed by neutral conditions(pH 7.4),and the slowest under acidic conditions(pH 3.0).The cumulative degradation rates within 35 days were 85%,64%,and 25%,respectively.In addition,the hydrogel remained in the mice for more than 5 weeks.The sericin hydrogel prepared by this hydrogel system has excellent mechanical properties.The compression modulus of 12% sericin hydrogel is 434 k Pa,and the maximum tensile length can reach 740%.In this case,the tensile strength is 375 k Pa.The sericin hydrogel is injectable.In addition,the sustained release time of the sericin hydrogel on horseradish peroxidase(HRP)was more than 192 h.In terms of cytocompatibility,it can support the adhesion and proliferation of mouse embryonic fibroblast cells(NIH 3T3).The above characterization results indicate that the sterile,injectable sericin hydrogels with high mechanical properties have the potential to be used as carriers for drugs,growth factors,or preparation for tissue repair materials.2.Preparation and application of transparent sericin hydrogels with high ductilityIn this part,the high concentration sericin solution was directly collected from the silk glands of the fibroin-deficient silkworm(140 Nd-s).Then high stretchable and transparent sericin hydrogel was prepared under the action of formic acid.The sericin hydrogel has good transparency and a porous three-dimensional structure.Its pore size ranges from 15-33μm,and its porosity ranges from 69%-80%.It indicates that sericin hydrogel has good breathability and is suitable for the growth of fibroblasts.The swelling rate of the sericin hydrogel is between 200%-260%.The degradation rate of hydrogel in aqueous solution is much slower than that reported in the past.Even under alkaline conditions(pH 11.0),the degradation rate at 5 weeks was only about 25%.This may be related to its high β-sheet structure and good stability.In terms of mechanical properties,the maximum elongation of the sericin hydrogel can reach 853% and the elastic modulus is 388 k Pa.In addition,the results of cell experiments showed that the sericin hydrogel was not cytotoxic and had good cytocompatibility.The results showed that the sericin hydrogel could be used as a visual wound dressing in the field of skin tissue repair.