Study On Preparation And Properties Of New Sericin Hydrogel

Sericin,one of the main proteins of silk,has good biological activity and no immunogenicity,and sericin has become a popular emerging biomaterial in the field of tissue engineering.In recent years,a variety of sericin hydrogels have been fabricated and used for tissue damage repair.However,the poor mechanical strength of these hydrogels restricted their applications.The mechanical property of sericin hydrogels is closely related to the concentration and molecular weight of the sericin before gelatinization.For the reason,this study explored the method of directly obtaining non-damaging,high-concentration sericin from silkworm bodies,on this base the hydrogel with high mechanical properties was fabricated by covalent cross-linking,and then the physical、chemical properties and cyto-compatibility of the hydrogel were systematically characterized,and the hydrogel with high mechanical properties were obtained,which provides new ideas and technologies for the development and application of new sericin materials.In addition,an interpenetrating double network hydrogel dressing based on sericin and polyacrylamide with high transparency is also reported in this paper.1.Research on high mechanical strength sericin hydrogel(1)Extraction and molecular weight identification of high concentration,non-damage sericin solutionThe silk fibroin-deficient silkworm variety 185 Nd-s was selected and fed to maturity at 5 instars under standard conditions.The central silk gland was dissected to obtain a thick sericin solution with a concentration of up to 16.1%(w/v).The molecular weight of the sericin was detected by polyacrylamide gel electrophoresis.The sericin extracted from the silkworm had five bands and the bands were complete without tailing,indicating that sericin maintains a certain molecular weight without being damaged.the sericin extracted from the silkworm can maintain a high integrity.(2)Fabrication of high mechanical property sericin hydrogel and optimization of cross-linking agentThe appropriate amount of hydrogen peroxide and sericin solution are mixed at room temperature to obtain sericin hydrogel.The results of the optimal ratio study of the amount of fully reacted cross-linking agent showed that the optimal ratio of sericin solution(16.1%,w/v)and hydrogen peroxide(3%w/v)was 100:1.8(v/v).Using optimized conditions mixing reagents and sericin.(3)Characterization of physicochemical properties of sericin hydrogelThe sericin hydrogel has a fast gel forming speed and can form a gel at room temperature for tens of seconds,indicating that the hydrogel can form gel in situ.Scanning electron microscope(SEM)was used to observe the microstructure of sericin hydrogel.The results showed that the sericin hydrogel lyophilized scaffold showed a porous network structure.The pore diameters obtained-80℃ and-196℃ were 62μm and 22μm respectively.the porosity of sericin hydrogel obtained-80℃ and-196℃ were 62%and 65%respectively.Infrared spectroscopy(FTIR)and X-ray diffraction(XRD)were used to evaluate the changes in the secondary structure of sericin.The FTIR detection results showed thatβ-fold,random coil,α-helix andβ-turn,the sericin solution lyophilized powder and sericin hydrogel are 35.62%,46.56%,0,17.82%and 38.30%,0,37.01%and 24.69%respectively.After sericin is gelled,a large number of irregular curls are converted intoα-helix structure,which enhances water Structural stability of the gel.XRD detection results showed that the characteristic peaks of the dihedral angle of sericin before and after gelation did not shift significantly,which proved that the crystal structure of sericin did not change significantly during the process of conversion to hydrogels.The results showed that the sericin hydrogel had good swelling performance,and the value of the maximum swelling rate was different under different pH conditions.Within 24 hours,the sericin hydrogel rapidly expanded and then slowed the expanding velocity.During the continuous expansion of 312 hours,the hydrogel swells up to 322%of its volume in an acidic environment,and swells to 352%and 398%under neutral and alkaline conditions,respectively.Sericin hydrogels are degradable,degrading 50%of the total mass during 45 days of degradation.Sericin hydrogel has excellent drug sustained release ability.It can maintain release for up to 40 days.The drug release is faster within 10 days.The cumulative drug release on the 10th day is 49%.then the release velocity was slowed,sustained release was up to 80%on the 40th day.the mechanical properties were tested with a universal testing machine,the results show that the sericin hydrogel has good mechanical properties,its maximum tensile strength is 80kPa,and its maximum compressive strength exceeds 800 kPa.The tensile strength and compressive strength of the hydrogel are much higher than the reported sericin hydrogel.In addition,the hydrogel has good elasticity.When the compression rate reaches 70%,the length of the hydrogel can be restored to 60%of the original length after unloading the external force.(4)Study on cell compatibility of sericin hydrogelThe hydrogel pieces were added into the cell culture plate containing mouse embryonic fibroblasts(NIH3T3)and cultured,and the cells in the cell culture plate containing no sericin hydrogel samples were used as controls at 24 h and 48 h time points.The method of cck8 detects the activity of cells.The results of the study showed that there was no significant difference in cell activity between the sericin hydrogel group and the control group,and the hydrogel was of no Cytotoxicity.2.Study on polyacrylamide-sericin interpenetrating double-network(IPN)hydrogel wound dressingBased on the previous research on the polyacrylamide-sericin interpenetrating double-network hydrogel,this article further explores the cytological properties of the hydrogel and its potential application in skin damage repair from the perspective of dressing.The research results show that the cell adhesion of sericin-polyacrylamide hydrogels fabricated by different formulations is different,and the cell adhesion of IPN hydrogels increases with the increase of sericin content.S50P50 sample had the best cell adhesion and no significant difference compared with the cells cultured in the conventional cell culture plate(control group).Observation of cell growth through a microscope revealed that the cells planted on the IPN hydrogel continued to proliferate with time.The cell density on the S50P50 sample was similar to that on the cell culture plate of the control group.The cell viability was detected by the cck8 kit.The cell viability of the IPN hydrogel increased with the sericin content.Among them,the cells with best viability were found on the S50P50,of which was no significant difference to the cells cultured on cell culture plate(control group).In addition,the hydrogel has high transparency characteristics,covering it on the wound surface of mouse,you can clearly see the wound surface without having to uncover the hydrogel dressing,indicating that the hydrogel is promising as a highly transparent wound dressing applying to skin damage repair.