| Cardiac valvular disease is very common in human being. The most popular therapeutic procedure for the cardiac valvular disease is valve replacement. Although remarkable advances toward an optimal valve replacement have been made over the past many years, the ideal prosthesis has not been achieved. Mechanical prosthesises are accompanied by a higher incidence of thromboembolism, bleeding, myocardial infarction and cerebrovascular accident. Biological valvular prosthesises, constructed from porcine aortic valves or bovine pericardium, can provide central blood flow, and freedom from life-long anticoagulation. However the durability of bioprosthesis remains unsatisfactory. Structural valve deterioration primary due to dystrophic calcification and stress-related tears or perforations is the most serious valve-related complication of bioprosthesis. Homograft valves also have a limited resources and durability. Biochemical fixation or cross-linked treatment has significant impacts on valvular calcification. Calcification of bioprosthesis is related to commissural bending strains.Stentless design could reduce such tissue stress, and also improve hemodynamic performance. So anticalcification treatment and stentless design are two main methods for improvement of bioprosthesis.Based on our proceed studies of bioprosthetic valve anticalcification, we used epoxy chloropropane and Triton X-100 treat porcine aortic valve pretreated by glutaraldehyde, and also adopted a new type stentless valve design. Early studies had confirmed that this bioprosthesis had very good performance in anticalcification. So in this experiment we placed emphasis on researching cytotoxicity, hemolysis and other physical and chemical properties of the bioprosthesis before clinical use. Method:1. Material and group(1). The valvular materials came from porcine aortic valve, which is treated by 3mL L"' glutaraldehyde 48 hours, 20 mL L"1 epoxy chloropropane 48 hours and 12mL L"1 Triton X-100 8 days in order, and persevered by 3mL L"1 glutaraldehyde.(2). Group GA group: Material only treated by glutaraldehydeEC group: Material treated by glutaraldehyde and epoxy chloropropane EC+Tr group: Material treated by glutaraldehyde, epoxy chloropropaneand Triton X-100Positive control: 4.5 mL L" hydroxyberzene or lacteprene Negative control: Saline or Polyethylene2. According to the methods of American ((ASTM standards for medical devices)) and the international standards,we made experiments of practices for evaluation toxicity of the valves by assessment of hemolytic properties,systemic injection in the mouse, and primary skin irritation in rabbits through evaluating material extracts.3. According to the methods of the ASTM standards, we made experiments of direct contact cell culture and MTT tests with material extracts to evaluate the cytotoxicity of the valve material.4. Biocompatibility research. We measured the valvular shrinkage temperature with our self-made shrinkage temperature meter, and measured degree of tissue wetness by comparing weight of valves of before and after 105'C, 2 hours treatment.5. Mechanical property research. We mearsured the maximum of tensile strength of the valve material with instronl!22 tensile force meter to evaluate their mechanical characteristics.Result:1. Biocompatibility studies. Hemolytic indexes of GA group, EC group, and EC+Tr group are 2.77%, 1.98% and 1.78%, respectively, lower than ASTM standard or our government standard. In the tests of systemic injection in the mouse, there is no mouse dead and no significant abnormal reaction. Primary skin irritation tests in rabbits also indicated that the valve material fit the ASTM standards.2. Direct contact cell culture test. In positive control group, there are many fragments and a decrease in the number of the L-929 cells, which indicates severe cell necrosis. In negative control, the growth of the cell is normal. In EC group and EC+Tr group, there are no apparent change... |
PDF Full Text Request