Electrospinning Of P(LLA-CL) And Surface Treatment Of P(LLA-CL) Nanofibrous Scaffolds By Heparinization

The anticoagulant properties of materials are essential to the implanted human biomaterials and medical equipment, which depends on the surface properties of the materials. Therefore, surface modification of materials is important to improve the blood compatibility of materials.This thesis mainly focused on the surface treatment of heparinization triggered by low temperature plasma for electrospun P(LLA-CL) nanofibers to improve blood compatibility.Surface modification of P(LLA-CL) using oxygen plasma was investigated in detail in this thesis. Besides, the mechanism of surface modification was analyzed through calculation of the weight loss rate of P(LLA-CL) before and after the treatment with oxygen plasma and the contact angle experiments. The experiment indicateed that the hydrophilicity of the P(LLA-CL) film increaseed after the plasma treatment, evidenced by the lowering of water contact angle from about 105°to 0°. The longer processing time, the higher rate of weight loss, but processing time increased to 60 seconds and longer, the rate had no longer increased, and the largest rate was 0.045(mg/cm²); The greater power of plasma processing, the higher the rate of weight loss, when increased to 60W power, the rate was the largest:0.025 mg/cm², and high-power, weight loss rate no longer increased.The thesis focused on study by plasma treatment, amination and heparinization respectively, as well as systematical study of preparation, blood compatibility and mechanical properties of the substate P(LLA-CL) material. In the work, the idiographic process of heparinnization: first,the oxygen plasma surface treatment was conducted, and then the straight chain diamine was selected as the space arm. Then,the hydrochloric acid ethyl-3-(dimethyl amino-propyl) carbon diimine (EDC) and N-hydroxy succinimide were employed as catalyzer to realize dehydration-condensation reaction, aiming to fix diamine on the P(LLA-CL) materials. The dehydration condensation reaction recurred when the amido on the other end of the diamine reacted with the the sulfonic and carboxyl in heparin molecular in acid deficient conditions. Heparin was thus immobilized on the surface of P(LLA-CL) materials and heparinized P(LLA-CL) materials were obtained.ATR-FTIR and EDS analysis proved that heparin had been grafted on the surface of P(LLA-CL). In the IR 3385cm^-1 a strong and broad characteristics of the infrared absorption peak formed, namely heparin molecule containing -COOH,-OH and -NH₂ groups characteristics of the role of the absorption peaks, but pure P (LLA-CL) in the infrared spectra of the 3385 cm^-1 did not appear similar characteristic absorption peaks. Besides, 1620 cm^-1 in the vicinity of pure spectra of heparin (1609 cm^-1) and heparininazation P(LLA-CL) spectra(1636cm^-1) had both aroylamino characteristic absorption peaks, and this indicated that heparin through aroylamino key was immobilized on the surface of the material. EDS analysis showed that the surface of electrospun P(LLA-CL) was composed of C (46.36%) and 0 (53.64%) atoms only. But after heparinization, the surface of electrospun P(LLA-CL) added Na (6.48%), Cl (6.88%) and S (0.80%) elemental composition. Obviously, all this elemental were from heparin.In vitro blood compatibility studies showed that simply plasma treatment cannot significantly improved blood compatibility of materials, but heparinization materials improved greatly. Calcium time experiment results showed that heparin after grafting P(LLA-CL) materials, the calcium time of heparinization materials had 8s longer than the time of the P(LLA-CL) without treatment; Experiment of the whole blood test time, after grafting heparin, the whole blood time of P(LLA-CL) longer than P(LLA-CL) and materials by plasma treatment alone.