Preparation And Study Of Polyglutamic Acid Based Multifunctional Biological Adhesive

In clinic,suture is still one of the main means of postoperative wound closure.Generally,the implementation of suture takes a long time,and the suture will cause secondary damage,which may cause further tissue damage and wound infection.More importantly,the suture generally cannot provide seal immediately to prevent fluid flow and air leakage.Compared with the application of seam and thread,biological adhesive has many advantages,such as easy operation,fast sealing,no pain and no need to remove the thread.In recent decades,biological adhesive has been proved to be an effective wound closure method.At present,all kinds of biological adhesives on the market have some disadvantages,such as long degradation time,poor biocompatibility,weak bonding strength,the risk of virus pollution caused by the source of raw materials,and the difficulty in offering the functions of hemostasis,sealing and tissue adhesion repair,which limit their clinical application.For that,this study would design a biological adhesive using natural polymer as raw material to fill the gap and deficiency of the existing commercial adhesive,and endow it with multi-functional characteristics of adhesion,hemostasis and repair.Our research strategies are as follows:firstly,the hydrogel bio-glue would be prepared by introducing TYR and tannic acid(TA)into the natural polyglutamic acid(PGA)chain through the use of the condensation agent 4-(4,6-dimethoxytriazine-2-yl)-4-methylmorpholine hydrochloride(DMTMM).As a natural polymer,PGA is easy to degrade and has good biocompatibility.Its inherent polar group can also improve the adhesion performance.The carboxyl group in the structure can provide the bio-glue with good hemostatic ability.TYR and TA can be grafted and crosslinked with PGA through amide reaction and esterification reaction.Both reactions can be carried out under the action of DMTMM,which can not only ensure that the bio-glue can be cured in situ at the bonding place,but also make the binder have possible crosslinking with the tissue;At the same time,polyphenol structure can endow bio-glue with strong adhesion on tissue surface and various materials;The combination of TA and TYR will enhance the adhesion.Because the single molecule of TA is large,it can increase the contact surface with the substrate,leaving a small vacancy,which can be filled by smaller molecule TYR,forming a more complete coverage on the substrate and more dense action sites,so as to enhance the bonding strength of the interface,and to achieve strong sealing effect and tissue bonding strength;TYR and TA will provide antioxidant properties of bio-glue and promote wound repair.The contents and results of this study are as follows:1.Firstly,we used the condensation agent DMTMM to catalyze amidation and esterification reactions to graft TYR and TA onto the long chain of PGA and prepared the bio-glue hydrogel.The results from IR,~1H NMR,thermodynamic analysis and SEM showed that TYR and TA grafted and crosslinked with polyglutamic acid through amidation reaction and esterification reaction,respectively,while the carboxyl,amino and phenolic hydroxyl groups of PGA,TYR and TA could form hydrogen bonds with each other,and the benzene ring structure could form dynamic physical crosslinks throughπ-πstacking.Bio-glue hydrogel had the shortest gelling time of about 1 minute and 50 seconds.Adhesion tests showed that the maximum adhesion strength of bio-glue hydrogel to pigskin,glass,rubber,stainless steel,PTFE,rabbit skin and sheep skin were 83.07±8.07 k Pa,229.11±4.73 k Pa,208.07±15.77k Pa,199.61±9.24 k Pa,54.68±2.27 k Pa,55.76±4.89 k Pa,49.95±13.11 k Pa,respectively,indicating that the hydrogel had strong adhesion properties to different materials.The lowest equilibrium swelling was about 8 g/g,and 84%degradation was completed in 15 days.2.The biocompatibility,blood compatibility and antioxidant properties of the bio-glue were further evaluated.After 1,4 and 7 days of coculture of bio-glue and L929 fibroblasts,the cell proliferation activity was higher than 90%,and the cell morphology was complete and the cells were evenly distributed,indicating that the bio-glue had good biocompatibility.In vitro hemolysis test showed that the hemolysis rate of biological binder was less than 5%.When the amount of bio-glue was 0.1 g/m L,the clearance rate of DPPH reached 77%,indicating good antioxidant performance.3.Finally,the liver bleeding model,liver injury model,full thickness skin incision model and xiphoid cartilage defect model of SD rats were established to verify the ability of bio-glue in liver hemostasis,liver repair,skin closure repair and cartilage repair.When used as a hemostatic agent,the amount of bleeding was reduced from 0.503±0.030 g to 0.086±0.015 g,showing a decrease of 82.9%.In the experiment of repairing the liver,the new liver tissue could be detected in the tissue filled in the defect of the bio-glue group 14 days after operation:the hepatic lobule of central vein was seen,also,the interlobular bile duct,interlobular vein and hepatic sinuses between hepatic cords in the portal duct area were observed;Neither obvious inflammatory cell infiltration nor cell swelling and necrosis was seen.In the wound closure experiment,the biological adhesive showed the ability to quickly close and repair the wound,and could replace the traditional surgical suture in function.In the experiment of cartilage repair,the area of new cartilage in the biological adhesive group was more than twice that in the blank group at each time point,and the distance between the broken ends was much smaller than that in the blank group,demonstrating its ability to fix cartilage and promote cartilage repair.