Construction Of QCS/MBG Shape Memory Cryogels And Its Anti-bacteria,Hemostasis And Promotion Of Wound Regeneration

Hemorrhage control remains a major challenge,especially for deep noncompressible wounds caused by gunshot and sharp objects.Hemorrhage is responsible for 30 to 40%of trauma mortality,and of these death,33 to 56%occur during the prehospital period.In the prehospital phase,hemostatic materials can potentially reduce morbidity and mortality through the early control of hemorrhage.However,traditional hemostatic methods such as gauze,tourniquets and direct pressure are not powerful enough for these extreme bleeding.Besides,porous zeolite,kaolin,gelatin sponge and hydrogel hemostatic agents are not suitable for these kinds of wound,and these materials have a single function and cannot further inhibit wound infection and promote wound healing after hemostasis.In this study,we proposed a novel multifunctional hemostatic agent,which can be used for non-compressed wound hemorrhage control,has excellent bactericidal properties and promotes wound healing.The cryogels are composed of quaternary ammonium chitosan（QCS）and mesoporous bioactive glass（MBG）.Glutaraldehyde crosslinked the amino groups on the QCS at low temperature to form a gel,and then freeze-dried to obtain a shape memory cryogel.Among them,MBG had the function of activating the intrinsic coagulation pathway and promoting wound healing.QCS aggregated blood cells through charge interaction to promote blood clotting and kill bacteria to avoid wound infection.The research on the physical and chemical properties,mechanical properties,antibacterial activity,biocompatibility,in vitro and in vivo hemostasis,and wound healing ability of cryogels has drawn the following conclusions:Firstly,MBG was prepared by the sol-gel method;Glycidyltrimethylammonium chloride was grafted with chitosan through the addition reaction to obtain QCS.The results of FTIR,XRD,SEM,TEM showed that we had successfully prepared quaternary ammonium chitosan,and the synthesized monodisperse amorphous mesoporous bioactive glass nanoparticles.The QCS/MBG cryogels were prepared by the freezing gel method,and the results of SEM and liquid absorption ratio showed that they had a connected macroporous structure with a pore size of 100-200 microns,and showed a large water absorption ratio of 53.45.Secondly,the mechanical test results showed that the degree of substitution of quaternary ammonium salt groups affects the cyclic compression performance of QCS cryogels.QCS_33%cryogels with a low degree of substitution exhibited brittleness and the material structure collapses after compression.The QCS_46%cryogel with a higher degree of substitution could maintain a stable structure after 10 cycles of compression,and it had a shape memory function.This is because QCS_33%has more amino groups to react with the cross-linking agent,resulting in high hardness of pore walls.The results of compressive stress and strain also showed that when the compression deformation was 60%,the stress of QCS_33%was 13.14 k Pa,which was much higher than QCS_46%of 5.49 k Pa.The QCS/MBG cryogels loaded with MBG using QCS_46%also maintains strong mechanical properties and cyclic compressibility.The results of the dynamic swelling ratio and the degradation experiment showed that it can maintain a stable structure in the PBS solution without collapsing,and at the same time had good degradability.Subsequently,whole blood clotting index（BCI）verified the effect of cryogels on promoting thrombosis.The results showed that QCS/MBG-0.8%had the best coagulation,and the coagulation index BCI was 10.34±3.24%.Hemostasis experiments in vivo further verified its coagulation effect.The bleeding time of liver prick injury was 71.58±9.11s,and the bleeding time of liver noncompressible wound hemorrhage was 46.94±0.92s,both of which were better than commercially gauze and gelatin sponge.The blood cell adhesion test,zeta potential and APTT test were further used to explore the hemostatic mechanism.The good hemostatic effect of QCS/MBG can be attributed to the synergistic effect of QCS adsorbing blood cells through charge interaction,MBG activation of the coagulation pathway,and QCS/MBG compression at the bleeding site to restore shape and form a physical barrier to block hemorrhage site.All these factors synchronized action to accelerate clotting process.Finally,the results of antibacterial tests showed that the bactericidal ratio of QCS/MBG cryogels was over 95%,indicating the excellent antibacterial property.Hemolysis and L929cell proliferation experiments showed that QCS/MBG cryogels had excellent blood compatibility,and their extract solutions can promote the proliferation of L929 cells,manifesting that it has the potential to promote the regeneration of defective tissues in vivo.Animal experiments further confirmed this effect.In summary,QCS/MBG cryogel had good hemostasis,antibacterial property and tissue regeneration ability,which had great potential for clinical application as a novel multifunctional hemostatic.