Analysis of stent expansion, blood flow and fatigue life based on finite element method / 医用生物力学

Objective To study the expansion behavior of stent in stenotic vascular, in stent blood flow and fatigue life of stent by finite element method. Methods ANSYS was used to simulate the expansion of stent in stenotic vascular. The blood flow model was created by constructing the entities based on deformation of the related nodes from the result of dilation process. A sample model was also built to simulate the in stent blood flow. Stent fatigue life was evaluated based on Goodman’s method and accumulated damage method, respectively. Results (1) Plastic deformation appeared on most parts of struts. The major stresses were localized in the corner of the slots. (2) Turbulent flow occured near the stent. Stresses of stent in cross section of bridge struts along the direction of blood flow were highest. (3) Goodman’s method showed that the stent was safe, and cumulative damage indicated that the largest cumulative damage occured in the second cross section of bridge struts. Conclusions Finite element method can be effectively used to simulate the stent expansion, in stent blood flow and stent fatigue life.

Fatigue life optimization for coronary stent under the effect of blood flow / 医用生物力学

Objective To evaluate the fatigue life of coronary stent under the effect of blood flow and thus optimize the stent design.MethodsA simplified model of the stent, blood, plaque and artery was established using Pro/Engineering, and the periodic blood flow impact on the vascular stent was simulated by finite element method via ANSYS. The result on hemodynamics from such stent was then used to evaluate its fatigue life. The geometric parameters of the stent were chosen as design variables for optimization. By using Latin Hypercubic sampling and ANSYS program, responses of the sample points could be obtained and the Kriging surrogate model was then constructed to optimize the fatigue life of the coronary stent.Results Goodman’s method showed that the optimized stent was safe. The cumulative damage method indicated that the largest damage occurred at the second cross-section of the bridge struts. The fatigue life of the optimized stent could be enhanced by 30.55%. Conclusions The finite element method can be used to evaluate the fatigue life of the coronary stent, and the optimization of stent by establishing Kriging model can effectively enhance the fatigue life of the stent.

Expression and purification of varicella-zoster virus glycoprotein I gene in insect cells / 中华预防医学杂志

<p><b>OBJECTIVE</b>To express the cloned gene glycoprotein I (gpI) of varicella-zoster virus (VZV), Beijing VZV 84-7 strain in insect cells and to purify its expression product.</p><p><b>METHODS</b>The gene coding for gpI of VZV was amplified from viral DNA by PCR and cloned into baculovirus transfer vector (pBacPAK9), and recombinant transfer vector plasmid pBacVZVgpI was obtained. The inserted gpI gene in the pBacVZVgpI was sequenced. Insect cells Sf 9 were co-transfected with the recombinant transfer vector plasmid pBacVZVgpI and wild type linear baculovirus BacPAK6 (digested with Bsu36I) DNA. The recombinant baculoviruses containing the VZV 84-7 gpI gene was isolated through several rounds of limited dilution. Recombinant protein gpI was expressed in insect cells Sf 9, postinfected with recombinant baculoviruses. The expressed recombinant gpI was purified by lectin affinity chromatography and its antigenicity and immunogenicity were investigated.</p><p><b>RESULTS</b>The gene coding for gpI of VZV was obtained by PCR and the gpI gene of pBacPAK9 was confirmed by DNA sequencing. The recombinant gpI was expressed in insect cells Sf 9, post-infected with recombinant baculovirus and identified by SDS-PAGE and western blotting, with its product in cell culture reaching the peak in 72 hours and with a molecular mass of 58 kd and 70 kd, the same as theoretical values. Results of immunoassay with cell lysates infected by recombinant baculoviruses indicated that recombinant protein expressed in insect cells had ability of eliciting specific antibodies against native VZV in mice and complement-dependent neutralizing antibodies. The purified recombinant gpI gave a product with a purity of more than 80%. ELISA and Western-blot analysis demonstrated that purified protein had specific VZV antibody-binding activity. This suggested that the recombinant gpI expressed in insect cells had the same biological characteristics as its native counterpart.</p><p><b>CONCLUSION</b>Baculovirus-insect cells could be used to express the gene of VZV gpI, which could provide a basis for quantitative analysis of VZV antigen, and preparation of its subunit vaccine.</p>