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A biomechanical model for simulating the deformation of a leukocyte adhered to the surface of a blood vessel under steady shear flow.

Xiaoheng LIU ; Xiong WANG ; Hua HUANG ; Huaiqing CHEN

Journal of Biomedical Engineering.2003;20(1):30-34.

The adhesion of leukocytes to substrate is an important biomedical engineering problem and has drawn extensive research. In this study, we have proposed a compound drop model to simulate a leukocyte with a nucleus adhered to the surface of a blood vessel under steady shear flow. A two-dimensional computational fluid dynamics (CFD) is conducted to determine the local distribution of pressure on the surface of the adherent model cell. By introducing the parameter of deformation index (DI), we have investigated the deformation of the model cell and it's nucleus under controlled conditions. Our numerical results show that: (1) the model cell is capable of deformation with the increase of initial contact angle, capillary number, and Reynolds number, and that the cytoplasm is more deformable while the nucleus is more capable of resisting external imposed shear flow; (2) the model cell is not able to deform infinitely with the increase of external shear flow because the deformation index reaches a maximum; (3) pressure distribution confirms that there exists a region downstream of the cell, which produces high pressure to retard continuous deformation and provide a positive lift force on the cell. Our results of nucleus deformation may help to develop a better understanding of how leukocytes transduce external mechanical signal like shear stress into nucleus.
Biomechanical Phenomena ; Blood Vessels ; cytology ; physiology ; Cell Adhesion ; physiology ; Cell Nucleus ; physiology ; Leukocytes ; physiology ; Models, Cardiovascular ; Numerical Analysis, Computer-Assisted

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Preparation of complex chitosan microcapsule and its application in controlled release of vitamin D2.

Xinyuan SHI ; Tianwei TAN

Journal of Biomedical Engineering.2003;20(1):26-29.

In this work a system which consists of chitosan (CS) microcores entrapped within enteric polymer is presented. Vitamin D2, used as a model drug, was efficiently entrapped within CS microcores using spray-drying and then microencapsulated into ethylic cellulose(EC). The morphology and release properties of microcapsules were tested. The influential factors of preparation conditions included molecular weight of chitosan, concentration of chitosan solution, concentration of acetic acid, loading of vitamin D2 were discussed. The results of in vitro release studies showed that the microcapsules prepared in this article could realize sustained release in intestine.
Capsules ; Cellulose ; analogs & derivatives ; pharmacology ; Chitin ; analogs & derivatives ; pharmacology ; Chitosan ; Delayed-Action Preparations ; Drug Compounding ; Drug Delivery Systems ; Ergocalciferols ; pharmacology ; In Vitro Techniques

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A study of bone-like apatite formation on calcium phosphate ceramics in different kinds of animals in vivo.

Yourong DUAN ; Yao WU ; Chaoyuan WANG ; Jiyong CHEN ; Xingdong ZHANG

Journal of Biomedical Engineering.2003;20(1):22-25.

Bone-like apatite formation on the surface of calcium phosphate ceramics has been believed to be necessary for new bone to grow on the ceramics and to be related to the osteoinductivity of the material. The research of bone-like apatite formation is a great help to understanding the mechanism of osteoinduction. Synthetic porous calcium phosphate ceramics (HA/TCP = 70/30) were implanted intramuscularly in pigs, dogs, rabbits and rats to make a comparative study of the bone-like apatite formation onto the porous HA/TCP ceramics in different animals. Specimens were harvested at 14 days after implantation. Samples were detected for the surface morphology with SEM. The chemical composition of the sample surface after implantation was analyzed with reflection infrared (R-IR). Obvious bone-like apatite formation could be detected in the sections of porous specimens harvested from all animals after 14 days intramuscular implantation. Crystal deposition could be only observed on the surface of the concave regions of the samples collected from dogs, rabbits and rat. On the contrary, evenly distributed flake-shaped crystal could be found on the pore surface and also on the outer surface of the materials implanted in pigs. The morphology of bone-like apatite in pigs was different from that in the others animals. Bone-like apatite was not observed in dense specimen implanted intramuscularly. Bone-like apatite formed faster on specimens implanted in rabbit than that in other animals. This formation sequence is different from the sequence of osteoinductivity of biphasic calcium phosphate ceramics implanted in these animals. The results demonstrated that the formation of bone-like apatite on materials is a prerequisite condition to their osteoinduction but other factors also play important roles in osteoinduction.
Animals ; Apatites ; chemical synthesis ; Body Fluids ; chemistry ; Bone Substitutes ; chemical synthesis ; chemistry ; Calcium Phosphates ; chemistry ; Ceramics ; chemistry ; Dogs ; Male ; Materials Testing ; Prostheses and Implants ; Rabbits ; Rats ; Swine

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Two sorts of problems on drug controlled release from swellable polymer.

Lingbing LI ; Yebang TAN

Journal of Biomedical Engineering.2003;20(1):17-21.

The mechanism of drug release from swellable polymer was studied. The model which can explain the drug release from glassy polymer was developed by coupling drug diffusion equation and solvent diffusion equation. The effect of viscoelastic stress of polymer was also considered. The Deborah number and swelling interface number were used to describe the mechanism of drug release, especially relax controlled mechanism.
Delayed-Action Preparations ; Diffusion ; Drug Delivery Systems ; Models, Chemical ; Polymers ; chemistry ; Tablets

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Study on the cytocompatibility of biodegradable poly(epsilon-caprolactone) microspheres in vitro.

Qizhi LUO ; Jianhai CHEN ; Kaijin DAI

Journal of Biomedical Engineering.2003;20(1):14-16.

Poly(epsilon-caprolactone) microspheres were fabricated with an average particle size of 5.08 +/- 0.23 microns. The effect of poly(epsilon-caprolactone) microspheres on apoptosis and cell cycle of fibroblast was studied with flow cytometry. The data obtained clearly indicated that poly(epsilon-caprolactone) microspheres purified in different ways showed different cytocompatibility. The well purified microspheres have good cytocompatibility.
Animals ; Biocompatible Materials ; chemical synthesis ; pharmacology ; Biodegradation, Environmental ; In Vitro Techniques ; Materials Testing ; Mice ; Microspheres ; Polyesters ; chemical synthesis ; pharmacology

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Elimination of methylene blue in plasma by use of adsorbents.

Yu MA ; Xiaolan YANG ; Xianjue TANG ; Shuhua JING

Journal of Biomedical Engineering.2003;20(1):11-13.

The adsorption of methylene blue (MB) in plasma on cross-linked agarose beads entrapped activated charcoal (CAAC-I), cross-linked agarose coated activated charcoal (CAAC-II) and cross-linked agar beads entrapped attapulgite (CAA) was tested in this study. These adsorbents are intended to be applied to blood purification for eliminating MB from virucidal MB-phototrated plasma units. The experimental results indicated that the adsorption of MB in plasma on CAAC-I and CAA was quick and efficacious, but it was slower on CAAC-II. The relationship between the adsorption time and the adsorption rate was examined with reference to the plasma with a specific concentration of MB flowing over a certain volume of CAA. A flow rate of about 1 ml.min-1 through 10 ml CAA at 25 degrees C could eliminate more than 95% of the MB in 200 ml human plasma (1 mumol.L-1).
Adsorption ; Agar ; chemistry ; Animals ; Charcoal ; chemistry ; Hemofiltration ; instrumentation ; Humans ; In Vitro Techniques ; Methylene Blue ; isolation & purification ; Rabbits

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Influence of different contact ways and extracting conditions on the hemolytic effect of biomaterials.

Jiao SUN ; Guozhen GU ; Yunfang QIAN

Journal of Biomedical Engineering.2003;20(1):8-10.

This assay was aimed to evaluate the influence of different contact ways and extracting conditions on the hemolytic effect of biomaterials. Using direct contact method and extract contact method, we assessed the hemolytic effect of PDLLA and PVC. The extracting conditions included: 37 degrees C 24 h, 37 degrees C 72 h, 37 degrees C 120 h, 50 degrees C 72 h, and 70 degrees C 24 h. After the material or extract had been in contact with the diluted blood of rabbit for certain times, the hemolysis rate was calculated. The results for PDLLA showed there were some differences between direct contact and extract contact at 37 degrees C for different extraction time (P < 0.05), but the hemolysis rates, lower than 5%, were in accord with the requirements of medical devices. However, under the condition of 50 degrees C and 70 degrees C, there were significant differences when extract contact method was compared with direct method (P < 0.01). For PVC, there was no statistically significant difference under all conditions (P > 0.05). Our conclusions: (1) Under the extracting condition of 37 degrees C from 24 h to 120 h, the soluble part of PDLLA and PVC that might influence erythrocyte did not dissolve considerably. (2) Under the extracting condition of 50 degrees C and 70 degrees C, the hemolysis rate may remarkably vary with the chemical characteristics of tested materials; (3) As to an unknown material, it is advisable to adopt two methods at the same time, one for direct contact and the other for extracontact. Thus the hemolytic effect of biomaterials can be evaluated from physical and chemical angles. (4) In case that the chemical property of the sample can endure the test, the extracting condition at 50 degrees C and 70 degrees C may be of benefit to assessing the hemolytic effect of biomaterials. (5) The extract contact method as a supplemental test of direct contact method is of realistic significance.
Animals ; Biocompatible Materials ; toxicity ; Hydrolysis ; drug effects ; In Vitro Techniques ; Materials Testing ; methods ; Rabbits ; Temperature ; Time Factors

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An investigation of HAP/organic polymer composite coatings prepared by electrochemical co-deposition technique.

Haobing HU ; Changjian LIN ; Yang LENG

Journal of Biomedical Engineering.2003;20(1):4-7.

An electrochemical co-deposition technique has been developed to prepare a hydroxyapatite (HAP)/organic polymer composite coatings on Ti surface as new biomaterial of hard tissue. The composite coating of organic polymer and calcium phosphate is formed by adding a water soluble polymer of the ethylene series to NH4H2PO4-Ca (NO3)2 solution when conducting an appropriate electrochemical co-deposition experiment. The XRD, SEM, XPS, SIMS and nano indent measurements were performed to characterize the morphology, composition, structure and surface stiffness of the composite coating. It was found that the morphology and surface hardness of the coatings showed a remarkable modification when introducing a minor polymer to HAP coating, and the bonding force between the coating and metal substrate was distinctly increased. The incorporation of minor organic polymer into the HAP compound at molecular level will improve the mechanical properties and morphology of the composite coatings, and this may be helpful to raising its bio-activity.
Coated Materials, Biocompatible ; chemical synthesis ; Durapatite ; chemical synthesis ; Electrochemistry ; Materials Testing ; Titanium ; X-Ray Diffraction

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Time-resolved fluorescence anisotropy measurement and its application in the research of biomacromolecule.

Daocheng WU ; Mingxi WAN

Journal of Biomedical Engineering.2002;19(4):712-714.

In this symposium, we reviewed the principle and development of time-resolved fluorescence anisotropy measurement. Its method of measurement, characteristics and applications in the research of biomacromolecule, configuration and molecular structure have been discussed. Its potential applications are also illustrated.
Fluorescence Polarization ; methods ; Macromolecular Substances ; Mathematics ; Models, Molecular ; Time Factors

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Radioprotective effects on head and neck tumors of amifostine--a broad-spectrum cytoprotection.

Rui HUANG ; Haifang YU ; Anren KUANG

Journal of Biomedical Engineering.2002;19(4):708-711.

Differentiated thyroid cancer can be effectively treated with high-dose 131I and the other head and neck cancer can also be effectively treated with extra-radiotherapy, but these treatments often result in a reduction in salivary gland function, causing xerostomia. Collectively, these effects can lead to severe secondary complications, including difficulty in speaking and swallowing, decreasing appetite even affecting nutrition and sleep. Amifostine, an analog of cysteamine, is a phosphorlyated aminothiol prodrug and its active metabolite, WR-1065 etc, can selectively protect normal tissues from the cytotoxic effects of drugs and/or radiation while preserve antitumor effects. Many studies have demonstrated that amifostine protects normal tissues from both acute and late extra-radiation damage without protecting the tumor. It has been approved by FDA to be used for protecting the salivary gland from xerostomia caused by radiotherapy. It has also show protecting effects on intra-radiotherapy, but there are many problems waiting for study.
Amifostine ; adverse effects ; therapeutic use ; Animals ; Clinical Trials as Topic ; Clinical Trials, Phase II as Topic ; Clinical Trials, Phase III as Topic ; Cytoprotection ; Head and Neck Neoplasms ; drug therapy ; radiotherapy ; Humans ; Rabbits ; Radiation Injuries ; prevention & control ; Radiation-Protective Agents ; pharmacology

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