Design of an axial blood pump of diffuser with splitter blades and cantilevered main blades / 生物医学工程学杂志

An implantable axial blood pump was designed according to the circulation assist requirement of severe heart failure patients of China. The design point was chosen at 3 L/min flow rate with 100 mm Hg pressure rise when the blood pump can provide flow rates of 2-7 L/min. The blood pump with good hemolytic and anti-thrombogenic property at widely operating range was designed by developing a structure that including the spindly rotor impeller structure and the diffuser with splitter blades and cantilevered main blades. Numerical simulation and particle image velocimetry (PIV) experiment were conducted to analyze the hydraulic, flow fields and hemolytic performance of the blood pump. The results showed that the blood pump could provide flow rates of 2-7 L/min with pressure rise of 60.0-151.3 mm Hg when the blood pump rotating from 7 000 to 11 000 r/min. After adding the splitter blades, the separation flow at the suction surface of the diffuser has been reduced efficiently. The cantilever structure changed the blade gap from shroud to hub that reduced the tangential velocity from 6.2 m/s to 4.3-1.1 m/s in blade gap. Moreover, the maximum scalar shear stress of the blood pump was 897.3 Pa, and the averaged scalar shear stress was 37.7 Pa. The hemolysis index of the blood pump was 0.168% calculated with Heuser's hemolysis model. The PIV and simulated results showed the overall agreement of flow field distribution in diffuser region. The blood damage caused by higher shear stress would be reduced by adopting the spindle rotor impeller and diffuser with splitter blades and cantilevered main blades. The blood could flow smoothly through the axial blood pump with satisfactory hydraulics performance and without separation flow.

Biological characteristics of a human specifically targeted antimicrobial peptide C16LL-37 against Streptococcus mutans / 华西口腔医学杂志

<p><b>OBJECTIVE</b>This study aimed to evaluate the biological characteristics of a human specifically targeted antimi- crobial peptide C16LL-37 against Streptococcus mutans (S. mutans).</p><p><b>METHODS</b>In this study, an antimicrobial peptide LL-37, a peptide derived from CSP(C16) (S. mutans competence stimulating peptide), and recombinant peptide C16LL-37 were synthesized by Fmoc-chemistry-based strategy. The selectivity and antibacterial activity of C16LL-37 were identified by the colony counting method on microbial culture plates. After treatment of C16LL-37 at 32 µmol · L⁻¹, the morphological changes in S. mutans were observed by using scanning electron microscopy (SEM). In addition, enzyme-linked immunosorbent assay was used to evaluate the hemolytic activity and antibacterial activity of C16LL-37 under different conditions.</p><p><b>RESULTS</b>1) The minimum inhibitory concentration of C16LL-37 was 16 µmol · L⁻¹, and the minimum bactericidal concentration was 64 μmol ·L⁻¹. 2) The survival rate of S. mutans was 3.46% after C16LL-37 treatment at 64 µmo-L⁻¹ for 30 min, whereas it was 0% at 64 µmol · L⁻¹ for 60 min. The survival rates of four other kinds of bacteria were more than 60% at any time (P < 0.05). 3) The morphological change in S. mutans was observed after C16LL-37 treatment at 32 µmol · L⁻¹ by using SEM. S. mutans presented an irregular shape, rough surface, and evident splitting. 4) The hemolysis rate of C16LL-37 (≤ 64 µmol · L⁻¹) was less than 0.33%. 5) This study showed no significant in- fluence on the antibacterial activity of C16LL-37 under different conditions, such as temperature, pH, salinity, and trypsin at low concentration (P > 0.05).</p><p><b>CONCLUSION</b>C16LL-37 exhibited obvious specificity for S. mutans, strong antibacterial activity, low toxicity, and high stability. Thus, C16LL-37 has good potential in caries research and clinical application.</p>

Comparison of CM-DIL and DAPI labeled bone marrow-derived mesenchymal stem cells / 中国组织工程研究

BACKGROUND:cellmarker technology has been widely applied in many studies concerning celltransplantation. Chlormethylbenzamido-1,1-dioctadecyl-3,3,3’3’-tetramethylin-docarbocyamine (CM-DIL) and 4’,6-diamidino-2-phenylindole (DAPI) are commonly used for labeling cells. To our knowledge, there are few reports on comparing the two fluorescent dyes. OBJECTIVE:To compare the effects of CM-DIL and DAPI on labeling bone marrow mesenchymal stem cells in vitro and in vivo. METHODS:Isolation and expansion of bone marrow-derived mesenchymal stem cells were performed according to attachment culture. The cells were labeled by CM-DIL and DAPI, respectively. cellviability was assessed via trypan blue exclusion assay. Growth curves of bone marrow-derived mesenchymal stem cells were depicted using MTS assay. The reduction of fluorescent intensity was observed under an inverted fluorescent contrast phase microscope from passage 1 to passage 3 after labeling. Myocardial infarction was induced by left anterior artery ligation in Sprague-Dawley rats. One week later, bone marrow-derived mesenchymal stem cells labeled by CM-DIL or DAPI were injected randomly into the border area of infarct myocardium. After 3 days, transplanted celldistribution was examined under the fluorescent microscope through paraffin sections and frozen sections respectively. RESULTS AND CONCLUSION:In vitro, bone marrow-derived mesenchymal stem cells labeled by both CM-DIL and DAPI showed decreased cellproliferation during the early period;the percentage of fluorescent-positive cells was approximately 100%in the two groups;however, the fluorescent intensity was significantly reduced from passage 1 to passage 3 in bone marrow-derived mesenchymal stem cells labeled by DAPI. In vivo, the transplanted cells were detected in a concentrated way both on the paraffin sections and frozen ones;the background color of frozen sections was lower in the CM-DIL group than in the DAPI group;false positive results of fluorescent expression could be eliminated in the CM-DIL group by using fluorescent mounting medium with the fluorescence of DNA staining. These data indicates that CM-DIL is more appropriate to in vivo tracing cells than DAPI.

Numerical simulation of LVAD inflow cannulas with different tips / 生物医学工程学杂志

The tip structure is one of the key factors to determine the performance of left ventricular assist device (LVAD) inflow cannulas. The tip structure influences the thrombosis, hemolysis in cannula and left ventricle and suction leading to obstruction in ventricle. We designed four kinds of inflow cannulas that had different tips and built the numerical models of the four historical used inflow cannulas inserted into the apex of left ventricle. We computed the hemodynamic characteristics of inflow cannulas insertion by Fluent software. We researched the backflow, turbulent flow and pressure distribution of the four inflow cannulas. The results showed that the trumpet tipped inflow cannula had smooth flow velocity distribution without backflow or low velocity flow. The trumpet tipped inflow cannula had the best blood compatibility characteristics. The trumpet structure could prevent obstruction. The caged tipped cannula had serious turbulent flow which could possibly cause thrombosis and the low pressure near left ventricle wall and easily lead to ventricle collapse. The trumpet tipped inflow cannula has the best blood compatibility and is difficult to be obstructed. The trumpet tipped inflow cannula is fit to long-term use LVAD.

Oral health status and its correlation with oral health knowledge among middle-aged people in Dongxiang, Bonan, and Yugur / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To provide basic data for the prevention of oral diseases in minorities by investigating the oral health status and behavior related to oral health knowledge of individuals aged 35 to 44 years in Dongxiang, Bonan, and Yugur.</p><p><b>METHODS</b>The caries and periodontal health of 445 individuals aged 35 to 44 years were examined according to the method and criterion prescribed by the World Health Organization and the Third National Oral Health Epidemiologic Investigation. A questionnaire survey on related oral health knowledge and behavior was conducted.</p><p><b>RESULTS</b>The crown caries prevalence rate in Dongxiang, Baoan, and Yugur were 48.28%, 79.47%, and 67.11%, respectively; the root caries prevalence rates were 38.62%, 69.54%, and 42.95%, respectively. The rates of gum bleeding in Dongxiang, Bonan, and Yugur were 86.90%, 90.07%, and 65.77%, respectively. The rates of dental calculus in Dongxiang, Bonan, and Yugur were 99.31%, 100.00%, 99.33%, respectively, and the rates of periodontal bags were 68.97%, 67.55%, and 43.62%, respectively. Only 69.84% of the respondents brush their teeth every day; 94.90% of the respondents do not floss. Only 20.19% of the respondents contact a doctor for a toothache, and 42.23% of the respondents have never seen a dentist.</p><p><b>CONCLUSION</b>Caries morbidity is high among the respondents aged 35 to 44 years from Dongxiang, Bonan, and Yugur. The periodontal health status and oral hygiene of the respondents are poor, and behavior related to oral health knowledge is insufficient. Thus, more attention must be provided to the prevention and control of caries and periodontal diseases among middle-aged people in the area.</p>

Experiment study of the acellular bovine pericardium treated by dye-mediated photooxidation used as engineering heart tissue / 中华胸心血管外科杂志

ObjectiveTo evaluate the feasibility of constructing tissue engineering cardiac patch with photooxidationfixed acellular bovine pericardium.MethodsFresh bovine pericardia were treated by dye-mediated photooxidation after decellularization.Some of them were seeded with bone marrow stromal cells(MSCs) isolated from male SD rats to construct cardiac patches.Myocardial infarction(MI) model was made in female SD rats by left anterior descending coronary ligation(LAD).One week later, the confirmed MI rats were divided into three groups randomly, group MI (n = 15)without any treatment; group P (n = 18) with photooxidated pericardia implantation ; group P + C (n = 18) with seeded pericardia implantation.A sham group (n = 10) was also performed with opening and closing chest twice only.The heart were explanted at 2 or 4 weeks after implantation, and examined histologically and immunohistochemically.The heart function was evaluated by echocardiography at 4 weeks before excising the rats.ResultsThere were no cells or cell debris remained in bovine pericardium tissue.The fiber structure became condensed after photooxidation.The seeded cells formed a continuous layer on the surface of the tissue.The pericardial degradation level and newly formed microvessel density were larger in group P + C than in group P after 2 [ (13.7 ±5.2)个/mm2 vs (7.1 ±3.1)个/mm2, P＜0.05]and4 [(22.6 ±4.9)个/mrn2 vs (14.1 ±5.3)个/mm2, P＜0.05]weeks.Four weeks after transplantation, cardiac echocardiography showed left ventricular ejection fraction(LVEF) was lower in group MI (44.8 ± 4.4) ％ and group P (48.4 ± 5.0) ％ compared with group P + C (49.3 ± 4.8) ％, left ventricular fractional shorterning(LVFS) was lower in group MI (18.0 ± 2.2) ％ and group P (19.8 ± 2.5) ％ compared with group P + C (20.4 ±2.5) ％, the difference between P + C and MI was significant.ConclusionTransplantation of the tissue engineered bovine pericardial patches with dye-mediated photooxidation can improve heart function in MI rats.This kind of patches demonstrates a promising prospect in the future.

Short term in vivo thrombosis evaluation of FW-Ⅱ axial blood pump for left ventricular assist / 中华胸心血管外科杂志

ObjectiveTo evaluate in vivo antithrombosis property of optimized FW-Ⅱ axial blood pump and provides evidence for future clinical use.MethodsA left ventricle-pump-descending aorta bypass model was established in five healthy sheep (60-70 kg) and the circulation of these sheep was assisted by FW-Ⅱ axial blood pump for 2 weeks.In preoperative and postoperative day 1,2,3,7,10 and 14,blood was drawn from the jugular vein to examine platelet activation and leukocyte-platelet aggregation respectively quantified with Annexin V,CD41/61 and CD14-PE by flow cytometry assays.Immediately after termination of the experiment,FW-Ⅱ axial blood pumps were explanted and each part was inspected for thrombus formation.Macroscopic and histological examinations were checked on heart,brain,kidney and spleen,respectively for thrombosis.ResultsCompared with preoperative baseline,the number of platelet activation and leukocyte-platelet aggregation reached a peak at postoperative day 2,it retained a high level within 7 days,then gradually decreased,but was still higher than preoperative level at dayl4.According to rotating speed,the number of platelet activation and platelet-leukocyte aggregation were lowest at the speed of 8000 r/min Minus thrombus were found in the front and rear hub of the pump rotor,and there was no thrombus at other components (flow straighter,impeller and pump housing).There were no ischemia and infarction evidences in macroscopic and histological examination of the heart,brain,kidney and spleen.ConclusionFW-II axial blood pump can be used to assist left ventricular circulation for 2 weeks with a satisfactory antithrombosis property.The level of platelet activation and leukocyte-platelet aggregation can be reduced to a lowest level at an optimized pump rotating speed.

In vitro evaluation of biodegradable cardiac tissue engineering polyurethane scaffold / 中国组织工程研究

BACKGROUND: In vitro construction of tissue engineered cardiac muscle becomes a hot spot in recent years, and the selection and design of scaffold is the key link. However, there is lack of ideal cardiac tissue engineering scaffold material. OBJECTIVE: To evaluate the novel biodegradable polyurethane in vitro, and to discuss the feasibility of polyurethane as cardiac tissue engineeru scaffold. METHODS: A new type polyurethane (PV-Lys) was synthesized using diphenylmethane-4,4'-diisocyanate as hard segment and lysine as expand chain. The tensile and suture strength were tested in vitro respectively, hydrolytic degradation was carded out in phosphate buffer saline of pH 7.4 at 37 ℃, and cytotoxicity was evaluated by MTT measurement and morphological observation. RESULTS AND CONCLUSION: The tensile strength of the polyurethane was up to (8.1±0.1) MPa, and the suture strength was (12.2+0.8) N. The average value of the mass loss of PV-Lys was (13.1+0.3)% at 8 weeks of in vitro hydrolytic degradation. MTT assay results showed that the cytotoxic grade of the novel PV-Lys was 0-1. Cell morphology observation showed that the L929 cells were spindle-shaped or tdangular with good stretch. This PV-Lys scaffold is with favorable mechanical property, cytocompatibility, biodegradable property, which meets the requirements of tissue engineering application.

Effect of proteins pre-coating on bone marrow mesenchymal cells retention and proliferation on decellular bovine pericardium / 生物医学工程学杂志

To observe the growth of rat bone marrow mesenchymal cells (BMMCs) on decellular bovine pericardia in vitro and to investigate the effect of proteins pre-coating on cells retention and proliferation, bovine pericardia were decellularized using trypsin, DNase and Triton X-100 respectively. Then three proteins (fibronetin (FN), gelatin, collagen I) were coated on the surfaces of the bovine pericardia separately. BMMCs were harvested from rat thighbone marrow , then expanded and seeded onto decellular bovine pericardia with the proteins pre-coated . Decelluar bovine pericardia without coating were used as controls. The retention and growth of BMMSCs were observed by Hochest staining and analyzed by MTT method. It was shown that the retention and proliferation of BMMCs on FN group and gelatin group were significantly enhanced comparing with those on collagen I group and control group (P < 0.001). There was no significant difference between FN group and gelatin group (P > 0.05), nor between collagen I group and control group (P > 0.05). We conclude that the retention and proliferation of seeding cells on FN and gelatin could be significantly improved on decellular bovine pericardia (DBP) but not on collagen I.

Biostability and calcification resistance of valved bovine jugular veins stabilized by dye-mediated photooxidation / 生物医学工程学杂志

This study was conducted to make an in vitro evaluation of the biological characteristic of valved bovine jugular veins stabilized by dye-mediated photooxidation. The fresh valved bovine jugular veins were stabilized by dye-mediated photooxidation. The glutaraldehyde-treated veins and fresh veins served as controls. The samples were subjected to protein extraction assay and pepsin digestion assay, and were analyzed by polyacrylamide gel electrophoresis. The rat subcutaneous model for assessment of tissue calcification and immunologic properties was used. Calcium levels were determined by elemental analysis on dried samples and von Kossa staining. Both photooxidized and glutaraldehyde-treated tissues were resistant to protein extraction and pepsin digestion, compared to fresh tissue. Calcification levels were much lower for photooxidized tissues when compared with those for both glutaraldehyde-treated and fresh tissues. The perigraft infiltrate was lower in the photooxidized tissues than in the fresh and glutaraldehyde-treated tissues. Valved bovine jugular veins stabilized by dye-mediated photooxidation were biostable and resistant to calcification, and the immunologic property was well.

Reconstruction of right ventricular outflow tract with bovine jugular vein valved conduit: a preliminary clinical report / 中华胸心血管外科杂志

Objective To summarize the experience in application of the bovine jugular vein valved conduct in right ventricular outflow tract (ROVT) reconstruction. Methods Totally 14 patients [6 male, (6.3?5.4) years old] underwent ROVT reconstruction from February 2004 to March 2005 was recorded, and the function of the implanted bovine jugular vein valved conduit was evaluated by Doppler echocardiography one month later after operation. Results There was no perioperative morbidity related to the bovine jugular vein valved conduit. 14 patients were discharged well. One month after operation, echocardiography showed that reconstructed ROVT was patent, and only four implanted conduits had mild regurgition. Conclusion The bovine jugular vein valved conduit provides the favorable hemodynamic performance and thus could be an excellent substitute for the homograft in the reconstruction of ROVT. The mid- and long-term outcomes required further study.

Study on tissue engineered patch replacing segment of the canine abdominal aorta / 中华胸心血管外科杂志

Ovbective To evaluate the feasibility of a tissue engineered patch constructed by a new copolymer of p(3HB-co-3HH) and polyurethane(PU) as in partial aortic replacement. Methods The autologous cell-polymer scaffold were used to replace 2.0～ 2.5cm abdominal aortic segments in dogs (group TE,n=6). The patches were seeded with 1?10 7 myofibroblasts each day for 4 days,and then 1?10 7 endothelial cells were seeded onto the scaffold. After 48 hours' incubation,the cell-polymer scaffolds were implanted to replace a segment of canine abdominal. In the control group (n=4),aortic segments were replaced with acellular polymer patches. No anticoagulation agent was used. At 2nd,4th,8th,12th,24th,and 48th weeks after operation,the seeded group animals were killed. The control group animals were killed at 4th,12th,24th,and 48th weeks. Explanted patches were examined histologically with scanning electron microscopy,and biochemically. Results In the group of TE patches,the tissue-engineered patches were covered with endothelium-like tissue macroscopically,and there was no thrombus formation on any of the specimens. Histological staining showed uniform layered tissue with endothelium and laminated fibrous tissue with collagen as predominant extracellular matrix. A confluent smooth surface was observed by scanning electron microscopy. An increase in the content of collagen and elastin was observed,and at 48th weeks after operation and their contents equaled to the level of native aorta. There was no endothelium formation in the acellular control,the collagen and elastin content were also smaller than that of the TE groups. Conclusion The autologous aortic grafts with biological characteristics resembling the native aorta can be created by using TE approach.