RESUMO
BACKGROUND: Axial-flow blood pump is a main pump for ventricle assistance. Previous researches demonstrate that poor hemocompatibility of blood pump is an important factor for hemolysis and thrombus.OBJ ECTTVE: To design an axial-flow blood pump based on previous kinds of blood pumps through changing whole appearance and impeller shape of the pump by using Computer-Aided Design CAD) and Computational Fluid Dynamics (CFD), and manufacture it successfully.DESIGN: Rationality of theoretical design was verified by practical tests.SETTTNG: Beijing Anzhen Hospital of Capital University of Medical Sciences Department of Biomedical Engineering,Beijing Institute of Heart, lung and Blood Vessel Diseases; the Faurteenth Institute of China-Aerospace Science and Industry Corporation.MATERIALS: Body of blood pump and impeller were titanium alligation, and shaft bearing was ceramic. Test in vitro was accorded to artificial ventricular assist device which was provided by Department of Biomedical Engineering, Beijing Anzhen Hospital of Capital University of Medical Sciences. Experimental goats were provided by Experimental Animal Center, Beijing Anzhen Hospital of Capital University of Medical Sciences.METHODS: Since the beginning of 2005, a model of axial flow blood pump was designed in the 14th Institute of China-Aerospace Science and Industry Corporation base on decreasing shearing force and circulating dead bands. In the process, CAD and CFD were used to generate the geometrical data document of pump's structure, which included the figures of pump's body, shape and number of impeller's vanes, the structure and position of the guide vanes, and the size of impeller's screw-pitch. And then, NC machine tool was used for shaping. Finally, axial-flow blood pump was fixed on artificial ventricular assist device which was provided by Department of Biomedical Engineering, Beijing Anzhen Hospital of Capital University of Medical Sciences. The pump's hemodynamic output was 5 L/min and the average pressure was 13.3 kPa under the mixture of glycerin and water and fresh anticoagulation goat blood. The samples were collected at every one half hour during pumps being pumping for 4 hours. According to testing pressure output of blood pump, normalized index of hemolysis (NIH) was used to reflect content of free hemoglobin in plasma, observe thrombogenesis in pump and verify pump's hemodynamic output and vascular damaging degree.RESULTS: Shaped axial-flow blood pump included body, impeller, guide vanes, ceramic shaft bearing, export and import. The volume was 63 mL. Experimental results in vitro indicated that when the rotation speed of blood pump was 10 000 r/min, its pressure and flow output were 21.01 kPa and 6.0 L/min. The hemodynamic output might satisfy for left ventricular assistance. Surface temperature did not change obviously during successive rotation. The calculation indicated that most parts in blood pump showed a streaming flow. The mean NIH was (0.047±0.017) g/100 L, which was less than that of previous pumps; while, thrombogenesis was not observed in blood pump.CONCLUSTON: Axial-flow blood pump designed by using CAD and CFD can not only satisfy for the hemodynamics of a left ventricular assistant devices, but also the blood damage is milder than previous pumps. Therefore, axial-flow blood pump improves blood compatibility.
RESUMO
<p><b>BACKGROUND</b>To explore the possibility of using retrovirus vector to carry HBV vector, and to prove that replication defective HBV could be normally packaged.</p><p><b>METHODS</b>Two kinds of full length of mutant HBV gene, which express dominant negative mutants, were inserted into retrovirus vector. After recombinant retroviruses were harvested, they were used to infect Hep G2 and 2.2.15 cell line. Then the expression of HBV core antigen in the Hep G2 cell was examined by immune fluorescence, and the existence of recombinant HB virion in the culture medium was examined by PCR.</p><p><b>RESULTS</b>High titer of recombinant retroviruses were obtained in the culture medium of transfected PA317 cell line. Core antigen was detectable in the recombinant retrovirus infected Hep G2 cell. Recombinant HB virion was detectable in the culture medium of recombinant retrovirus infected 2.2.15 cell.</p><p><b>CONCLUSIONS</b>The results suggested that recombinant retrovirus could carry HBV vector and express HBV products. When structural protein is offered by wt-HBV, the recombinant retrovirus may function as HBV vector, therefore it could be used in anti?HBV gene therapy.</p>