Study On Modification Of Bovine Pericardium Material With Tannic Acid

The functional components of horticultural products not only have nutritional and health functions,but also have important application value in the medical industry.Artificial heart valves mainly include bioprosthetic valves and mechanical valves.Bioprosthetic valves are obtained by chemical treatment of heterogenous pericardial tissues.They have good hemodynamic properties and low thrombosis rate,but their mechanical properties are poor.They are prone to calcification(calcium phosphate deposition),which is not conducive to long-term use.At present,the durability and anti-calcification properties of bioprosthetic valves have been greatly improved by glutaraldehyde and other cross-linking agents.However,glutaraldehyde-crosslinked pericardium has certain cytotoxicity and is prone to calcification decay,so the long-term effect is not ideal.Based on glutaraldehyde cross-linking,tannic acid(TN),a natural biological cross-linking agent rich in horticultural products,was used to modify bovine pericardium.It is expected to construct heterogeneous bioprosthetic valves with good cell compatibility and durability to prolong the service life of the valves.The main results are as follows:(1)The standardized procedure of membrane removal was established,and the warm ischemia time was controlled within 2 hours to prevent the tissue from further metabolizing and destroying the tissue structure after isolation,to effectively remove the adipose tissue on the surface of pericardium without destroying the tissue structure of pericardial fibrous layer,and to carry out bacteriostasis treatment to maintain the best performance of pericardial materials.(2)In order to reduce the immunogenicity of xenogeneic tissues,the fresh bovine pericardium was acellular treated with nuclease detergent.The acellular effect was observed by appearance,HE staining,DAPI staining,mechanical properties,SEM and TEM.It was found that after acellular treatment,the cell structure decreased,the mechanical properties increased,and the fiber structure was exposed.The mechanicalproperties of the acellular group(CE)were improved compared with that of the uncellular group(UCE).(3)The acellular pericardium was immobilized with glutaraldehyde(GA)and then modified with tannic acid(TN).Because tannic acid is astringent,it binds to collagen in the pericardium and coagulates proteins.The appearance,HE staining,mechanical properties,SEM and TEM observation were compared with those of glutaraldehyde group.After TN treatment,the toughness increased and the mechanical properties improved.SEM and TEM observation showed that the collagen fibers arranged compactly,regularly and uniformly after TN treatment,which were better than those of other groups.(4)Bovine pericardium specimens were implanted subcutaneously on the back of SD rats for 30 and 90 days.The calcification degree of the patients was simulated by subcutaneous implantation of SD rats.After removal,the pericardial specimens of each group were intact without obvious damage.Cytotoxicity of pericardial specimens of each group was detected in vitro.Calcification after embedding was observed by pathological section staining such as Von Kossa staining,HE staining and PSR staining.The results showed that TN treatment had high cytotoxicity and serious calcification,and the cytotoxicity was grade 2.It indicated that the cell compatibility of the materials treated with TN was poor,and the phenomenon of calcification was easy to occur,which might be related to the large exposure of collagen fibers.