Preparation And Properties Of Mesoporous Silica/Tannin Composite Hydrogel Hemostatic Materials

In daily life,pre-hospital blood loss and infection are two major challenges to human life safety.Timely hemostasis is one of the main measures to reduce mortality.Therefore,it is particularly important to develop multifunctional biomaterials with hemostatic and antibacterial properties.Mesoporous silica material can activate FXII coagulation factor and carry out endogenous coagulation because of its negative charge on its surface;With mesoporous structure and capillary effect,it can absorb water in blood and make blood cells aggregate.Therefore,it is widely used as a hemostatic agent in clinic.However,the poor adhesion between mesoporous silica and other inorganic hemostatic agents limits its application in massive hemorrhage.Tannin is a natural plant polyphenol.As a dopamine derivative,tannin is rich in catechol and pyrogallol structures.Because the rich-OH groups on benzene ring can form strong hydrogen bonds with hydrophilic surfaces,they can adhere to body tissues and quickly seal wounds,thus stopping bleeding quickly;Catechol and pyrogallol groups can be adsorbed on the surface of bacterial cell wall,which physically kills bacteria and makes the material have certain antibacterial effect.Organic materials based on polyacrylamide hydrogel have a three-dimensional network structure,which can absorb exudate,keep the wound moist,protect the wound,resist the invasion of external bacteria and reduce the chance of wound infection;However,its poor mechanical properties,hemostatic effect and antibacterial performance limit its application.Therefore,mesoporous silica and tannin can be combined with hydrogel,which can improve the mechanical properties,hemostatic properties,antibacterial properties and antioxidant properties of hydrogel,and at the same time reduce the wound residue of mesoporous silica in the hemostatic process.In this study,mesoporous silica with different morphology and pore structure,tannin and acrylamide were used as raw materials to prepare multifunctional hydrogel hemostatic materials with good hemostatic,antibacterial,mechanical properties,tissue adhesion and antioxidant properties.The specific research contents are as follows:（1）Mesoporous silica with different morphology,pore structure,particle size,and pore size were prepared by the sol-gel method.The morphology and physical properties of the prepared mesoporous silica materials were characterized by scanning electron microscopy,transmission electron microscopy,and specific surface area tester.The results showed that spherical mesoporous silica with disordered pore structure（SMS）,cashew-shaped mesoporous silica with two-dimensional hexagonal ordered pore structure（SBA-15）,and spherical silica nanoparticles（SNP）were successfully synthesized.Their mesoporous silica materials have high specific surface area（SMS:505 m²/g,SBA-15:666 m²/g）and large pore volume（SMS:0.39 cm³/g,SBA-15:0.82 cm³/g）.Spherical silica has homogeneous particle size（SMS:300 nm,SNP:300 nm）.（2）The effects of silica doping content（0.6 wt%,1.4 wt%,2.2 wt%）on swelling rate,mechanical properties and hemostatic properties of hydrogel were investigated by controlling the type of silica and the doping content of tannin（6.4 wt%）.The experimental results show that the swelling ratio and compressive strength of the hydrogel increase at first and then decrease with the increase of mesoporous silica content.The compressive strength of the hydrogel increases by 33%-167%and reaches 1.55 MPa.SMS doped with 1.4 wt%had better hemostatic performance.Compared with gauze,the bleeding volume was reduced from 2318 mg to 37 mg,and the bleeding time was reduced from 662 s to 200 s.The experimental results show that the addition of tannin makes the material have better antioxidant and antibacterial properties.With the increase of tannin content,the antibacterial properties of the composites increased,and the antibacterial rate increased from 21.6%to 81.6%.（3）In order to further improve the antibacterial and hemostatic effect of hydrogel,PAAM-TA-SMS with the best hemostatic effect was selected and modified,SMS was loaded with Ag⁺,and Ca²⁺was crosslinked with hydrogel to prepare Ag/Ca/SMS/tannin composite hydrogel.The experimental results show that Ag⁺loading has little effect on the specific surface area,pore volume and pore size of SMS.The introduction of Ag⁺and Ca²⁺had no effect on the chemical structure of the hydrogel,and the mechanical properties and swelling rate of the hydrogel decreased,but the antibacterial and hemostatic effects were enhanced,and the antibacterial rate increased from 21.6%to 83.5%.Compared with SMS doping,the hemostatic time was shortened from 200 s to 169 s,and the bleeding volume was reduced from 37 mg to 30 mg.To sum up,Ag/Ca/SMS/tannin composite hydrogel has the best hemostatic and antibacterial properties.In summary,the prepared mesoporous silica/tannin composite hydrogel hemostatic material has excellent hemostatic,antibacterial and antioxidant properties.This work improves the hemostatic properties of the material and promotes blood coagulation from various aspects.It provides theoretical basis and practical application significance for the research and development of multifunctional hemostatic materials in the future.