摘要:

AbstractThe adsorption of fibrinogen and plasminogen from plasma to silica glass, sulfonated silica glass, and lysinederivatized silica glass has been investigated. The data indicate that the sulfonated material has a high affinity for both fibrinogen and plasminogen, but that the ratio of plasminogen to fibrinogen is greater on the lysinederivatized surface. The adsorption data also suggest plasminogen as a possible contributor to the fibrinogen Vroman effect, whereby initially adsorbed fibrinogen is displaced from the surface. The plasmin activity of plasminogen adsorbed to the lysine‐derivatized silica glass and its sulfonated precursor was assessed by both a chromogenic substrate assay and a radioimmunoassay for the plasmin cleavage product of fibrinogen, the Bβ 1–42 peptide. The data indicate that (1) the adsorbed plasminogen is not inherently plasmin‐like; (2) the enzymatic activity associated with the bound plasminogen is significantly enhanced on both surfaces in the presence of activator; and (3) in the presence of activator, the plasmin activity per mole of bound plasminogen on the lysinized material is approximately a factor of two greater than on the sulfonated material based on the chromogenic substrate assay, and a factor of four greater based on the Bβ 1–42 radioimmunoassay. The lysinized material thus exhibits several properties that are different from its sulfonated precursor. It adsorbs more plasminogen relative to fibrinogen after the Vroman peak, and this adsorbed plasminogen appears to be in a conformation that is more readily activated to plasmin. Once activated, the surface bound plasmin shows enhanced ability to cleave either a low molecular weight chromogenic substrate or a macromolecular substrate. These properties appear to be directly related to lysine residues on the surface and may be the result of specific conformational changes occurring when plasminogen engages its lysine binding sites. © 1994 John Wiley

ISSN:0021-9304    

DOI:10.1002/jbm.820280402

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractPorous‐coated Ti‐6Al‐4V has a fatigue strength approximately one‐third that of the uncoated alloy. The interfacial geometry between the porous coating and the implant substrate is notchlike, leading to stress concentrations that have been shown to be the main cause for the reduction in fatigue strength. In this study, the effect of interfacial geometry on fatigue strength of porouscoated Ti‐6Al‐4V is quantified. The interface between porous coating and implant is modeled using linear elastic, plane strain finite element analysis. Integrated with the numerical analysis is an experimental verification of enhanced fatigue behavior. Changes in interfacial geometry are conceived, and their effectiveness in reducing stress concentrations are determined. A doubling of fatigue strength can be achieved for newly conceived geometries over conventional porous coating geometries. © 1994 John Wil

ISSN:0021-9304    

DOI:10.1002/jbm.820280403

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effects of Ag+1, Au+3, Cd+2, Cu+2, Ga+3, In+3, Ni+2, Pd+2, and Zn+2on DNA synthesis, protein synthesis, succinic dehydrogenase activity, and total cellular protein of mammalian fibroblasts were measured for exposures less than 12 h. The rates at which these cellular functions responded to metal ion exposure were compared and related to the uptake rate of the ions into the cells. These rates of response were significantly different: DNA synthesis decreased the fastest, followed by protein synthesis, succinic dehydrogenase activity, and total protein. This order of response was similar for most metal ions. At 4 h, the rate of uptake of the metal ions correlated most closely with depression of succinic dehydrogenase activity, whereas at 8 h, the uptake correlated most closely with depression of protein synthesis. The similar response of cells to all metal ions may imply that these ions act on cells by similar mechanisms. The rates of uptake of Ag+1, Cu+2, and Zn+2were sufficiently fast thatin vivoexposures of tissues to these metals for periods less than 12 h would be capable of disrupting cellular metabolism. © 1994 John Wiley&Sons, Inc

ISSN:0021-9304    

DOI:10.1002/jbm.820280404

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effect of material composition and shear rate on fluid‐phase platelet activation was investigated using a capillary perfusion model. Citrated whole blood was perfused along the lumens of tubes constructed from silicone, PVC, Pellethane, W124 (an experimental polyetherurethane), and glass. Platelet activation was determined by measuring the increase in α‐granule membrane protein P‐selectin (GMP‐140, CD62) and the lysosomal granule membrane protein GP‐53 (CD63) on fluid‐phase platelets by flow cytometry. All tubes caused an increase over the negative control in the number of P‐selectin and GP‐53 molecules detectable on the surface of these platelets. The activation response of platelets to changes in shear rate was also investigated. It was found that lysosomal release paralleled α‐granule release in glass, but not in Pellethane, over a range of wall shear rates (100–1,000 s−1). © 1

ISSN:0021-9304    

DOI:10.1002/jbm.820280405

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to derive new mathematic formulae that could be used reliably to predict water permeability of surgical fabrics before they are made and tested for water permeability. Such a theoretical prediction of water permeability, Qprd, of surgical fabrics is needed for not only timely characterization but also for assisting in more efficient future design and development of better surgical fabrics. Two mathematic formulae, Qwand Qk, were derived from the Buckingham Pi Theorem, in which relevant fiber and fabric parameters were placed into dimensionless π groups and computed for 25 commercial and experimental vascular fabrics. Linear regression analysis of the relationship between these π groups with water permeability on the woven and knitted grafts yielded coefficients for the corresponding π groups that were required for constructing appropriate mathematic formulae to predict water permeability of vascular fabrics. When proper sources of the experimentally determined water permeability, Qexp, were chosen for comparison, we found that 86% of woven fabrics (6 of 7) and 77% of knitted fabrics (14 of 18) had their Qprdwithin 10% of their Qexp. This high percentage of close matching (within 10%) between Qprdand Qexpshould be considered satisfactory because the experimental error for obtaining Qexpis generally higher than 10%. The difference between Qprdand Qexpranged from as small as 0.27% to as high as 74.2%, depending on the type of fabrics and source of Qexp. It appeared that the formulae worked well with fabrics of simpler structure such as those experimental woven vascular fabrics that showed 100% close match between Qprdand Qexp. Nonlinear relationship among the parameters and additional new parameters are required to fine‐tune for existing mathematic formulae to improve their accuracy of predicting water permeability for more complex fabric structures such as knitted fabrics. A computer program had been written that uses these theoretical formulae for predicting water permeability of vascular fabrics. Users could simply input five major fabric and fiber parameters of a surgical fabric and the computer would calculate its water permeability instantaneously. © 1994 John Wiley&Sons

ISSN:0021-9304    

DOI:10.1002/jbm.820280406

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractParamagnetic alginate beads with a 10–100 μm size range have been developed. These beads, when activated with chloroacetic anhydride and covalently coupled to avidin (30 μg/mg beads), were able to bind biotinylated goat anti‐mouse (B‐GAM) antibody (Ab). The beads with immobilized antibody were then used as a model system for the capture and non‐enzymatic release of CD34+ (KG1a) cells. A maximum of 82% KG1a (average = 65 ± 16.1%) cell capture, and 57% (average = 51 ± 5.9%) cell release has been attained using this model system. Optimization of the system in terms of further bead size reduction, and in terms of developing a system to recover released cells with high purity, will make an excellent system for cell capture and nonenzymatic release. © 1994 John Wil

ISSN:0021-9304    

DOI:10.1002/jbm.820280407

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractA cationic, high‐water‐content hydrogel membrane composed of poly(vinyl alcohol) (PVA) and poly(allylbiguanido‐co‐allylamine) hydrochloride (PAB) with positively charged biguanido groups that resemble arginine residues was developed. The PAB was prepared by reacting poly(allylamine) hydrochloride (PAA) with guanyl‐O‐methyl isourea. PAB/PVA hydrogel membranes were prepared by repeated freezing and thawing. For comparison, hydrogel membranes composed of PAA and PVA were also prepared. The interaction between these hydrogel membranes and mouse fibroblast (L929) was studied by a cell culture method. The PAB hydrogel blend had a relatively low percentage of initial cell attachment. The cell growth on the PAB hydrogel membranes showed a maximum at 5 mol % PAB content that was as high as commercially available plastic films. However, cells on hydrogel membranes with 50 mol % PAB content and 0 mol % PAB content (only PVA) did not seem to grow; neither did the 5/95 PAA/PVA membranes. Water contact angles of hydrogel membranes did not vary with the PAB content. Morphology of the cell attachment was observed by SEM. On the PAB blend hydrogel surfaces, cells were not spindle‐shaped and monolayers, but rather cells aggregated in spherical clusters. © 1994 John W

ISSN:0021-9304    

DOI:10.1002/jbm.820280408

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractAspergillus oryzae, Mucor mucedo, andPhycomyces blakesleeanuscultures were examined as sources of chitin/chitosan. The nitrogen content of the alkali‐treated mycelia/sporangiophores ofA. oryzae,M. mucedo, andP. blakesleeanuswas 2.52, 3.61, and 6.27% w/w, which relates to an estimated chitin content of 37, 52, and 91%, respectively. The effect of these fungal materials on the rate of proliferation of human F1000 fibroblasts in culture was examined. At 0.01% w/v, all three materials exhibited significant (P<.05) proproliferant activity over a period of 13 days. However, at 0.05% w/v,P. blakesleeanusfurther enhanced cell proliferation, whereasA. oryzaeandM. mucedoproduced a significant (P<.05) antiproliferant effect. Higher concentrations ofP. blakesleeanus(0.1 and 0.5%) caused marked inhibition of F1000 cell proliferation when measured on days 3 and 6. Only the proproliferant effect of these fungal materials appears to correlate to their chitin content. Furthermore, the cytomorphology of the fibroblasts indicated thatP. blakesleeanus, and to a lesser extentM. mucedo, possessed cell attractant properties, again correlating with chitin content. If developed for use as wound management materials, the sporangiophores ofP. blakesleeanusand the mycelium ofM. mucedocould possibly promote the growth of fibroblasts and provide a matrix for their anchorage, thus contributing to the granulation phase of the healing cascade. © 1994 John Wiley&Sons, I

ISSN:0021-9304    

DOI:10.1002/jbm.820280409

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractThe objective of this work was to investigate the interactions of poly(D,L‐lactic acid) nanoparticles prepared by a recently developed salting‐out process, with lymphocytes and monocytes isolated from healthy human donors. Nanoparticles were labeled with a hydrophobic fluorescent dye and incubated with lymphocytes and monocytes, and their uptake was followed by flow cytometry in the presence and absence of plasma. Plasma protein adsorption increased nanoparticle uptake by monocytes, whereas a decrease of cellular binding of the nanoparticles to lymphocytes was noted. The cellular uptake for both cell types consisted in a passive adsorption and in an energy requiring process, because the cells became 2–3 times more fluorescent when the incubation temperature was increased from 4 to 37°C. When nanoparticles were coated with polyethylene glycol 20,000, uptake by monocytes decreased by 43 and 78% in phosphatebuffered saline and plasma, respectively; a similar decrease in nanoparticle uptake was observed for lymphocytes. Two‐dimensional gel electrophoresis was performed to identify the plasma opsonins adsorbed onto the nanoparticle surface. Protein mappings for uncoated and polyethylene glycol‐coated nanoparticles differed for two spot series. These spots, not yet clearly identified, may represent specific apolipoproteins involved in the metabolism of human lipoproteins, indicating the possible involvement of specific receptors in the uptake of the nanoparticles. © 1994 John Wile

ISSN:0021-9304    

DOI:10.1002/jbm.820280410

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY

摘要:

AbstractTwo kinds of polyetherurethane (PEU), U‐3 and U‐8, were coated in thin layers on an ethylene‐vinylalcohol copolymer (EVAL) film 0.1 mm thick. U‐3 is a nonsegmented PEU prepared from 4,4′‐diisocyanatodiphenylmethane (MDI) and poly(tetramethylene oxide) of Mn = 1,000 (PTMO 1000), and U‐8 is a segmented PEU prepared from MDI, PTMO 1000, and 1,4‐butanediol. The coating thicknesses were 0.0068 and 0.022 mm for U‐3 and U‐8, respectively. These coated films were implanted subcutaneously into rats and retrieved after various weeks. The coatings on the retrieved samples were dissolved in tetrahydrofuran (THF), and the average molecular weight (MW) was determined by injecting the THF solution into a gel permeation chromatograph. In the case of U‐3, MW increased after 2 weeks, then decreased over the implantation period. After 10 weeks, U‐3 almost disappeared from the base film. In the case of U‐8, MW reached the maximum at 4 weeks postimplantation then decreased gradually over the implantation period. The rate and degree of MW change were greater in U‐3 than in U‐8. Here, we argue that, in the early stage, low molecular weight PTMO/MDI oligomers leached out from the PEUs to the inflammatory exudate to increase MW, and in the later stage macrophage attachment/activation had a role in the degradation of PEUs. The surface morphologic changes observed by scanning electron microscopy are also discussed

ISSN:0021-9304    

DOI:10.1002/jbm.820280411

出版商:John Wiley&Sons, Inc.    

年代:1994

数据来源: WILEY