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Biomedical subjects

R E Marchant

Publications and source records attributed to R E Marchant.

At least 19 recordsLinked to original sources
PubMed1995

Adhesion of Staphylococcus epidermidis to biomedical polymers: contributions of surface thermodynamics and hemodynamic shear conditions.

Adhesion studies of Staphylococcus epidermidis RP62A were conducted using a rotating disk system to determine the roles of surface physicochemistry and topographies under physiologic shear conditions. Six materials were investigated: biomedical reference polyethylene and polydimethylsiloxane; argon plasma-treated reference polyethylene (Ar-PE); Silastic; expanded polytetrafluoroethylene; and woven Dacron. All of the polymers except Dacron demonstrated reduced bacterial adhesion with increasing shear stress. Argon plasma treatment of polyethylene reduced the level of staphylococcal adhesion. Adsorption of human plasma proteins effected significantly lower numbers of adherent bacteria. The lowest adhesion was observed for Ar-PE in 1% human plasma protein solution, whereas Dacron had the highest number of adherent bacteria. The high adhesion on Dacron was attributed to increased bacterial flux caused by topography-induced turbulent flow and physical entrapment of the bacteria in the fiber interstices. The results indicate that the driving force for S. epidermidis adhesion is strongly influenced by substrate physicochemistry, but this may be dominated by physical forces such as shear and turbulence.

Bacterial Adhesion↗
PubMed1995

Cell-surface receptors and proteins on platelet membranes imaged by scanning force microscopy using immunogold contrast enhancement.

High resolution scanning force microscope (SFM) images of fibrinogen-exposed platelet membranes are presented. Using ultrasharp carbon tips, we are able to obtain submolecular scale resolution of membrane surface features. Corroboration of SFM results is achieved using low voltage, high resolution scanning electron microscopy (LVHRSEM) to image the same protein molecule that is seen in the SFM. We obtain accurate height dimensions by SFM complemented by accurate lateral dimensions obtained by LVHRSEM. The use of 14- and 5-nm gold labels to identify specific membrane-bound biomolecules and to provide contrast enhancement with the SFM is explored as a useful adjunct to observation of unlabeled material. It is shown that the labels are useful for locating specific protein molecules on platelet membrane surfaces and for assessing the distribution of these molecules using the SFM. Fourteen nm labels are shown to be visible over the membrane corrugation, whereas 5-nm labels appear difficult to resolve using the present SFM instrumental configuration. When using the 5-nm labels, collateral use of LVHRSEM allows one to examine SFM images at submolecular resolution and associate function with the structures imaged after the SFM experiment is completed.

Blood Platelets↗
PubMed1994

Interactions of human von Willebrand factor with a hydrophobic self-assembled monolayer studied by atomic force microscopy.

Human von Willebrand Factor (vWF) was studied by atomic force microscopy under physiologic buffer on a hydrophobic octadecyltrichlorosilane self-assembled monolayer. The self-assembled monolayer deposited on glass was sufficiently smooth (root mean square roughness = 0.25 +/- 0.12 nm) to permit identification of adsorbed vWF. Adhesion of the protein to the hydrophobic substrate was sufficient to allow repeated scanning by the atomic force microscope probe, and images of vWF on a submolecular scale were obtained. The frictional force between the surface and the protein was sufficient to withstand an applied lateral force of 19 nN. This result shows that vWF experiences strong interaction with a hydrophobic surface in aqueous media. Statistical analysis of adsorbed vWF shows that the protein is composed of large globular domains with elliptical cross sections of average dimensions 56 +/- 24 nm (major axis) 26 +/- 19 nm (minor axis), and 2.8 +/- 1.0 nm (height). Further analysis of the major axis dimension shows that the molecular chain of vWF contains two statistically different populations of domain size. However, no sequence order of the different domains within the individual molecule was found. On the basis of our analysis of the globular domains, we present a model describing the three-dimensional structure of vWF protomer adsorbed on a hydrophobic surface in a physiologic solution.

Adsorption↗
PubMed1994

Interactions of plasma proteins with a novel polysaccharide surfactant physisorbed to polyethylene.

A polysaccharide surfactant, dextran-[1,6 bis(2-hydroxypropyl-1-amine)hexane]-dextran, (D-H-D) was prepared by reacting dextran (Mw = 8200) with epichlorohydrin followed by reaction with 1,6-hexanediamine. The D-H-D polymer product was characterized by gel permeation chromatography (GPC), and 13C-nuclear magnetic resonance spectroscopy (13C-NMR). D-H-D was physisorbed on polyethylene (PE) from aqueous solution, and the adhesion stability and resistance to protein adsorption was examined under static and dynamic flow conditions, using a modified rotating disk system. Modified surfaces were characterized by attenuated total reflectance Fourier transformed infrared spectroscopy (ATR-FTIR), electron spectroscopy for chemical analysis (ESCA) and by water contact angles. Under applied shear stresses of up to 73 dyn cm-2, the adhesion of D-H-D on PE was sufficient to inhibit desorption by water (> 90% D-H-D on PE was retained) and 5% SDS surfactant solution (approximately 83% D-H-D retained), as determined by ATR-FTIR. Under similar shear stress conditions, albumin adsorption on D-H-D modified PE was reduced by over 90%, and protein adsorption from fresh human plasma was reduced by approximately 70% compared with unmodified PE. The results are discussed in terms of interfacial forces, and the suitability of this approach for studying protein-surface interactions and for developing a novel class of protein-resistant biomaterials.

Adsorption↗
PubMed1992

Cytokine and growth factor production by monocytes/macrophages on protein preadsorbed polymers.

These studies evaluate the effect of biomedical polymers: Biomer, polydimethyl-siloxane (PDMS), polyethylene, expanded polytetrafluoroethylene (ePTFE), Dacron, and the control polystyrene with or without adsorbed proteins IgG, fibrinogen, and fibronectin on the ability of activated human monocytes/macrophages to produce Interleukin 1 Beta (IL-1-B), Interleukin 6 (IL-6), and Tumor Necrosis Factor Alpha (TNF-A). Monocytes/macrophages incubated on biomedical polymers with or without protein preadsorption produce variable levels of IL-1-B, IL-6, and TNF-A dependent on the polymer and adsorbed protein. IL-6 was produced in the greatest quantity and was the most influenced by protein adsorption. ePTFE and PDMS polymers were least stimulating while polystyrene was the most stimulating of monocyte activity. Adsorbed IgG consistently altered the ability of the polymers to activate monocytes/macrophages to produce cytokines. These studies provide important insight into conditions which modulate monocyte/macrophage activity in response to protein preadsorbed biomedical polymers.

Adsorption↗
PubMed1992

Biocompatibility studies on plasma polymerized interface materials encompassing both hydrophobic and hydrophilic surfaces.

The biocompatibility of radiofrequency plasma polymerized films (less than 100 nm thick) deposited on biomedical polymer supports has been characterized by in vitro and in vivo methods. The polymer interface materials covered a wide range of elemental composition and surface properties, and were prepared from N-vinyl-2-pyrrolidone, gamma-butyrolactone, n-hexane, and hexamethyldisilazane (PPHMDSZ). The biocompatibility studies showed that the interface materials were noncytotoxic to mouse and human fibroblasts, as shown by morphologic evaluation, and by determination of extracellular LDH; and they did not stimulate interleukin-1-like production from human monocytes, as indicated by a thymocyte proliferation assay. The human fibroblast proliferation assay showed that three of the polymers supported cell growth at levels comparable to, or greater than, polymer controls, while the hydrophobic PPHMDSZ inhibited both cell attachment and proliferation. The response to subcutaneous implantation for all test materials was indicative of biocompatibility, with rapid resolution of the acute phase response and normal wound healing. The wide range of composition and surface properties for the plasma polymerized films evaluated in this study suggest that this general class of materials is likely to exhibit excellent biocompatibility.

Animals↗
PubMed1992

The immobilization of glucose oxidase onto radio-frequency plasma-modified poly(etherurethaneurea).

Glucose oxidase was covalently immobilized onto a radio-frequency plasma-modified poly(etherurethaneurea). Thin (90-100 nm) plasma-polymerized N-vinyl-2-pyrrolidone films were deposited onto poly(etherurethaneurea) films. Active sites for the immobilization were obtained via reduction with aqueous sodium borohydride and activation with 1-cyano-4-dimethylaminopyridinium tetrafluoroborate. Modified poly(etherurethaneurea) films were assayed for binding and activity of the immobilized glucose oxidase layer. The results of a modified radioimmunoassay and an 'immunochemical stain' indicated that washing in 900 ml of continuously stirred 2% sodium dodecyl sulfate, 2% Triton X-100, and 20 mM sodium phosphate, pH 7.0, for 24 h each at 4 degrees C was necessary to remove physically adsorbed glucose oxidase from the solid supports. An amperometric activity determination in 9 ml of well-stirred 20 mM sodium phosphate-0.1 M sodium chloride, pH 7.4, gave a qualitative demonstration of the activity of the immobilized enzyme on 18.75 cm2 of modified poly(etherurethaneurea) film. A colorometric activity determination using the coupled reaction with o-dianisidine and peroxidase indicated that glucose oxidase covalently immobilized on approximately 2.4 cm2 of modified poly(etherurethaneurea) film had an activity approximately equal to that of 13.4 nM glucose oxidase in 50 mM sodium acetate, pH 5.1, with a specific activity of approximately 32.0 U/mg at pH 5.1 and room temperature.

Biocompatible Materials↗
PubMed1990

A hydrophilic plasma polymerized film composite with potential application as an interface for biomaterials.

A hydrophilic polymer composite film (approx. 420 nm thick), with potential application as an interface for biomaterials has been prepared on nonorganic substrates, which include glass, silicon, and aluminum foil, using a glow discharge plasma polymerization technique. A thin film (110 nm thick) polymerized from hexane provided an adherent protective coating for the substrate material, and covalent bonding sites for the outer layer polymerized from N-vinyl-2-pyrrolidone. This outer layer provided the hydrophilic surface or interface. The two layers were copolymerized for a short period during transition between monomers to provide an intimate covalently bonded diffuse interphase. Preliminary in vitro and in vivo biocompatibility studies indicate that the hydrophilic film is non-cytotoxic, and does not increase the inflammatory response when compared with negative controls.

Animals↗
PubMed1990

In vivo leucocyte interactions on Pellethane surfaces.

In vivo leucocyte interactions of three Pellethane materials of varying hardness were qualitatively and quantitatively characterized using a cage implant system over a 21 d implantation period. Scanning electron microscopy (SEM) and cytochemical staining were utilized to observe the cellular events occurring at the leucocyte-biomaterial interface. Many of the quantitative assays performed, the intracellular alkaline phosphatase activity of exudate leucocytes, the intracellular acid phosphatase activity of adherent leucocytes, the density of adherent leucocytes and the foreign body giant cell network formation tendencies of adherent leucocytes, suggest increased cellular activation with increased Pellethane hardness. Qualitative SEM evaluation of Pellethane surfaces revealed a variety of cellular activities. These included macrophage adherence, cytoplasmic spreading and macrophage-macrophage membrane fusions to form foreign body giant cells. The foreign body giant cells exhibited nuclear reorganization and, when compared with adherent macrophages, they displayed an enhanced ability to fuse to neighbouring leucocytes, increased spreading of membrane processes over the polymer surface, the presence of large cytoplasmic vacuoles, and a lengthened duration of enzymatic activity. Contact angle analysis showed the Pellethane surfaces to be hydrophobic and of low hysteresis. The critical surface tension and the dispersive component of the total surface tension were found to increase with Pellethane hardness.

Alkaline Phosphatase↗
PubMed1989

Effect of albumin coating on the in vitro blood compatibility of Dacron arterial prostheses.

A recirculating in vitro perfusion system was used to assess the effect of albumin precoating on the thrombogenicity of Dacron vascular grafts. A complete analysis of platelet activation was carried out, involving platelet count, release, adhesion and aggregation. Fibrin formation was assessed by measuring fibrinogen levels and fibrinopeptide A production; leucocyte interaction was analysed by measuring total leucocyte count as well as an analysis of cell adhesion to the surface by scanning electron microscopy. The platelet count decreased progressively with perfusion time for Dacron until by 30 min, it had declined to 69% +/- 2% of baseline. The platelet count did not, however, change significantly from baseline when albumin-coated Dacron was tested. Release of platelet factor 4 and beta-thromboglobulin at 180 min for Dacron was 37.8 +/- 29.8 times and 66.9 +/- 18.2 times baseline, respectively, while albumin coating caused significantly less (P less than 0.03) platelet release. Albumin coating diminished coagulation activation and fibrinopeptide A formation. The total leucocyte concentration decreased significantly for Dacron by 180 min, while that for albumin-coated Dacron did not change significantly from baseline levels. Albumin coating produced a film-like covering over the Dacron. For Dacron, there were numerous leucocytes and platelets adherent to the surface, whilst cellular deposition was minimal upon the albumin-coated surface. Thus, albumin coating improved the short-term blood compatibility of Dacron by all of the methods employed in this study.

Albumins↗
PubMed1989

The cage implant system for determining in vivo biocompatibility of medical device materials.

Biocompatibility of an implanted material, drug delivery system, or prosthetic is a dynamic two-way process that involves the time-dependent effects of the host on the material and the material on the host. Implantation of any synthetic material initiates a wound-healing mechanism that is characterized by the inflammatory response. We have developed a novel implant system that enables quantitative as well as qualitative evaluation of the inflammatory response to implanted materials. The cage implant system can be used to quantify the cellular and enzymatic components of inflammation and permits access to study cellular adhesion and interactions with candidate biomaterials. The basic methodology of the implant system is described. The effectiveness of the system is illustrated by comparing the results for three contrasting materials: polyethylene, poly(vinyl-chloride) containing a stabilizer that is cytotoxic, and poly(DL-lactide) containing hydrocortisone acetate.

Animals↗
PubMed1987

Vascular graft-associated complement activation and leukocyte adhesion in an artificial circulation.

Complement-associated leukocyte adhesion appears to be a consistent in vitro and in vivo finding for many types of polymers; however, very little work has been done on the interaction of leukocytes with vascular graft materials. An in vitro perfusion system was used to study complement and leukocyte activation associated with the following vascular graft materials when tested with human blood: expanded polytetrafluoroethylene (ePTFE), crimped Dacron Bionit (DB) and preclotted Dacron Bionit. A decrease in the total leukocyte concentration with perfusion time was seen for all materials tested, and paralleled leukocyte adhesion to the graft surface as observed by scanning electron microscopy. The most dramatic decrease in leukocyte concentration was observed for the interaction of heparinized whole blood with Dacron. This was due to a selective decrease in neutrophils and monocytes, and was correlated with an increase in both leukocyte adhesiveness and complement activation, as measured by C5a elevation. Inhibiting complement activation by use of the anticoagulant, sodium citrate, curtailed Dacron-induced leukocyte adhesion. Little leukocyte or complement activation was observed for ePTFE or the silicone rubber control regardless of the anticoagulant used.

Adult↗
PubMed1987

In vivo leucocyte interactions with the NHLBI-DTB primary reference materials: polyethylene and silica-free polydimethylsiloxane.

In vivo leucocyte interactions with the NHLBI-DTB primary reference materials, low density polyethylene (LDPE) and silica-free polydimethylsiloxane (PDMS), were qualitatively and quantitatively characterized using a cage implant system over a 21 d implantation period. Scanning electron microscopy (SEM) and cytochemical staining procedures were utilized to observe the cellular events occurring at the leucocyte/biomaterial interface. The results showed that more cells adhered to the PDMS surface than the LDPE surface at days 4 and 7. The differential analysis revealed that mononuclear cells, presumably macrophages, preferentially adhered to both polymer surfaces. By day 21, there were more very large (greater than 20 nuclei per cell) foreign body giant cells (FBGCs) present on the PDMS surface than the LDPE surface. The phagocytic capabilities of the adhered cells, including the FBGCs, decreased to a greater extent on the PDMS surface, corresponding to the earlier and more extensive spreading of these cells observed in the morphological analysis.

Alkaline Phosphatase↗
PubMed1986

In vivo biocompatibility studies. VII. Inflammatory response to polyethylene and to a cytotoxic polyvinylchloride.

The cellular biocompatibility of low-density polyethylene and a cytotoxic polyvinylchloride were investigated using an in vivo cage implant system. Components of the inflammatory response (white cells, extra-cellular alkaline and acid phosphatase, the complement component C3, and total protein content) were monitored over a 21-day implantation period. Scanning electron microscopy was used to evaluate the morphologic condition of leukocytes adherent to the implanted polymers. Prior to implantation, each polymer was evaluated using an established primary acute toxicity screen. The results showed that the cytotoxic polyvinylchloride stimulated an intense acute phase inflammatory response, and at later observation periods, an intense and increasing chronic inflammatory response. In contrast, the polyethylene promoted relatively small increases in the acute and chronic phases of inflammation; the overall cellular response being essentially resolved by the third week after implantation. The initial toxicity screen of each polymer suggested that the observed differences in inflammation were primarily caused by the release from the polyvinylchloride of the added cytotoxic agent (dioctyltinbisoctylmercaptoacetate).

Acid Phosphatase↗
PubMed1986

The effects of an enhanced inflammatory reaction on the surface properties of cast Biomer.

The ability of a biomaterial to withstand the rigors of the harsh biologic environment is an important consideration when considering a material for long-term biomedical applications. Using a cage implant system, the effects of an intense inflammatory reaction on cast Biomer have been investigated. The inflammatory response to cast Biomer was greatly increased by coimplanting Biomer films with a cytotoxic poly(vinyl chloride) (PVC) in rats for a period of 21 days. Cast Biomer films were characterized by weight, advancing contact angle with water in air, attenuated total reflectance infrared spectroscopy and scanning electron microscopy (SEM). The analyses were performed before any treatment, after autoclaving and sonication, and after 21 days implantation with the cytotoxic (PVC) in rats. The results of the study indicated that cast Biomer does not undergo significant chemical degradation when subjected to the effects of an intense inflammatory reaction for 21 days. Implantation does, however, lead to rearrangement that results in a more polar and hydrophilic surface, suggesting that the polymer adapts to the hydrophilic environment of the inflammatory exudate.

Animals↗
PubMed1983

Type V collagen during granulation tissue development.

The collagen content, as determined by hydroxyproline assay, of experimental granulation tissue in rats was observed to increase rapidly 21 days, and less rapidly to 90 days of tissue development. Resistance of the collagen to pepsin digestion reached a maximum at 21 days, suggesting more extensive or more stable crosslinking at that time. Type V collagen and the expected collagen types I and III were present in pepsin extracts of the granulation tissue as determined by SDS-polyacrylamide gel electrophoresis. Over 3 months of tissue development the relative quantity of type V collagen, as evidenced by changes in the alpha B chain, varied in parallel with the changing vascularity of the tissue, suggesting an association with capillary endothelial cells and angiogenesis.

Animals↗
PubMedDate not supplied

In vivo biocompatibility studies. V. In vivo leukocyte interactions with Biomer.

A cage implant system was utilized to quantitatively and qualitatively characterize in vivo leukocyte interactions with cast Biomer. Scanning electron microscopy (SEM) in conjunction with cytochemical staining procedures were used to investigate the cellular events at the leukocyte/Biomer interface as well as in the inflammatory exudate over a 21-day implantation period. SEM was used to characterize leukocyte morphology on the Biomer surface and the cytochemical stains were used to differentially count leukocytes and to demonstrate intracellular alkaline and acid phosphatase activity. The results showed that the population density of leukocytes on the Biomer surface diminished with implantation time. The population density of multinucleated foreign body giant cells remained constant with time, while the numbers of nuclei per giant cell increased. The differential analysis revealed that macrophages preferentially adhered to the Biomer surface compared to other leukocytes in the exudate. The phagocytic capability of all adherent leukocytes, including giant cells, decreased with time and this corresponded to changes in leukocyte morphology observed with SEM.

Acid Phosphatase↗