摘要:

AbstractThese studies evaluate the effect of biomedical polymers: Biomer, polydimethylsiloxane (PDMS), polyethylene, expanded polytetraf luoroethylene (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 bi

ISSN:0021-9304    

DOI:10.1002/jbm.820260702

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe biocompatibility of surgically implanted materials may be compromised as a consequence of inflammatory reactions associated with phagocyte activation. Two important mediators of the inflammatory response are Interleukin‐1 (IL‐1) and tumor necrosis factor (TNF), both of which exert a wide range of biologic effects on many cells. This study was designed to evaluate the release of these cytokines by human monocytes (HM) brought into contact with four biomaterials utilized in clinical practice: polyurethane, expanded polytetrafluorethylene (ePTFE), Dacron velour, and woven Dacron. In vifro cultures for the generation of IL‐1 and TNF by HM in the presence of the above biomaterials were established by exposing cells to each bio material in the presence and absence of lipopolysaccharide (LPS) with harvest of supernatants after 6 or 18 h. These studies showed that in the absence of LPS, IL‐1 was released only by Dacron velour and woven Dacron associated monocytes while TNF was secreted in response to all of the materials. When LPS was present, however, monocytes associated with all of the materials released IL‐1; and TNF release was greatly augmented. Further, the quantity of released cytokine was directly related to the duration of the association time. This study demonstrated that HM in association with various biomaterials were ctivated to produce both TNF and IL‐1 and that the addition of nanogram quantities of LPS, such as would be produced if infection were present, greatly increased the amount of cytokin

ISSN:0021-9304    

DOI:10.1002/jbm.820260703

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe suitability of polymeric biomaterials as surfaces for the attachment and growth of cells has often been investigated in tissue culture. In this study the contribution that adsorption of serum fibronectin (Fn) or vitronectin (Vn) make to the attachment and spreading of fibroblast cells during the first 90 min following seeding was determined for two modified tissue culture polystyrenes, as model biomaterial surfaces. The amount of serum Vn and Fn which adsorbed onto tissue culture grade polystyrene (TCP) from different serum concentrations over the range of 0.1‐30% (v/v) were determined and compared to attachment of cells of the BHK‐21 and HT1080 fibroblast lines. There was no simple correlation between the amount of Fn or the amount of Vn adsorbed and cell attachment and spreading. The requirement for Fn or Vn for attachment and spreading of BHK‐21 or HT1080 cells onto modified polystyrene (either TCP or to Primaria) during the first 90 min of cell culture was directly tested by selective removal of Fn or Vn from the serum prior to addition to the culture medium. Attachment and spreading of BHK‐21 or HT1080 cells onto TCP or Primaria surfaces were reduced in a concentration dependent manner when the cells were seeded in medium containing 2% (v/v) or higher concentrations of Vn‐depleted serum. BHK‐21 cells or HT1080 cells seeded in medium containing Fn‐depleted serum (which contained Vn) attached and spread onto TCP or Primaria. Both BHK‐21 cells and HT1080 cells failed to attach to TCP or Primaria when seeded in medium containing serum depleted of both Vn and Fn. The requirement for serum Vn or Fn for fibroblast attachment to TCP was also tested using cells of a human dermal fibroblast strain. The attachment of the dermal fibroblasts to TCP during the first 90 min of culture was not decreased by depletion of Vn from the 15% (v/v) serum, but there was a reduction in the proportion of the attached cells which had spread. Selective depletion of serum Fn did not have any effect on either cell attachment or spreading. Our results show that for fibroblast cells, particularly with cell lines such as BHK‐ 21 or HT1080 but also with cell strains, the first binding of cells onto tissue culture polystyrene when plated in medium containing serum is a result of adsorption onto the surface of serum Vn. The adsorption of serum Vn onto the surface overcomes the effect of serum components which tend to decreas

ISSN:0021-9304    

DOI:10.1002/jbm.820260704

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThis study determined the bone formation in porous calcium carbonate (CC) and porous hydroxyapatite (HA) in ectopic sites. The bone formation stimulus was derived from bone marrow cells. CC and HA in the shape of disks were implanted with or without rat marrow cells into subcutaneous sites of syngeneic rats. The CC and HA had identical microstructure: pore size was 190–;230 μm, porosity was 50–60% and they were fully interconnected. Bone did not form in any implants without marrow cells (disks themselves), whereas bone consistently formed in the pores of all implants with marrow cells after 4 weeks. The bone formation of both CC and HA occurred initially on surface of the pore regions and progressed toward the center of the pore. Scanning electron microscopy and electronprobe microanalysis revealed a continuum of calcium at the interfaces of both bone/CC and bone/HA implants. These results indicate that the bone formation in calcium carbonate derived from marine corals is comparable to the bioactive hydroxyapa

ISSN:0021-9304    

DOI:10.1002/jbm.820260705

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractAllogeneic demineralized bone (DB) powder was applied to subcutaneous pockets and cranial defects of rats and histological, histomorphometrical, and radiological evaluation was performed one to 52 weeks after implantation. In both type of implants cartilage formation was observed after 1 week between DB particles and in former vascular channels and crevices within the particles. Foci of bone formation were observed after 2 weeks in the center of the implant. Remineralization of DB particles only occurred in close contact with the new bone tissue by which they became incorporated, indicating that remineralization of DB is a continuation of a process which has started in live bone. At all times, the interface between implant and connective tissue of the host consisted of a layer of nonremineralized DB particles embedded in fibrous connective tissue. This rim was thinner at the dura‐mater‐side in the cranial implants, compared with the skin‐side of the same implants as well as all sides of the subcutaneous implants. The rim became thinner with time but never disappeared completely. The outer contour of the mineralized implant sometimes ran right through a DB particle. A critical concentration of bone‐inducing agent leaking from DB particles seems to be necessary for bone induction. We suggest that at the interface of the implant and loose connective tissue this concentration is never reached, which results in maintenance of

ISSN:0021-9304    

DOI:10.1002/jbm.820260706

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe biocompatibility of radiofrequency plasma polymerized films (<100 nm thick) deposited on biomedical polymer supports has been characterized byin vitroandin vivomethods. The polymer interface materials covered a wide range of elemental composition and surface properties, and were prepared fromN‐vinyl‐2‐ pyrrolidone, γ‐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 bi

ISSN:0021-9304    

DOI:10.1002/jbm.820260707

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractAcrylic bone cement containing hydroxyapatite (HA) as a filler was developed using 4‐methacryloyloxyethyl trimellitate anhydride (4‐META) to promote adhesion both to bone and HA. The mechanical strengths of the cement did not decrease significantly with increasing HA in the cement by 4‐META. However, strengths decreased with increasing HA content in the absence of 4‐META. Scanning electron micrographic examination of fractured surfaces of the cement clearly showed that the HA particles adhered to the matrix resin when 4‐META was added. Thus, it was important to maintain the original mechanical strengths for 4‐META. The HA particles along the surface increased with increased HA content in the cement. The cement adhered to bone with a tensile bond strength was higher

ISSN:0021-9304    

DOI:10.1002/jbm.820260708

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractMore radiolabeled thrombin was adsorbed to heparin‐polyvinyl alcohol (PVA) than to PVA, consistent with a specific interaction with the immobilized heparin. The maximum surface concentration on heparin‐PVA was estimated to be ∼450 nmol/m2with an apparent affinity constant (Ka,) of 2.5μM−1; on PVA, the plateau concentration was 10 nmol/m2with a Ka<1 nM−1. There was little difference in bovine serum albumin (BSA) adsorption between PVA and heparin PVA. Interestingly, thrombin adsorption to polyethylene was indistinguishable from that to PVA despite the large difference in surface chemistry. BSA adsorbed to polyethylene with higher affinity than to the hydrogels, although the plateau concentrations were comparable. The adsorbed thrombin was biologically inactive at least towards chromogenic substrate, with the residual activity on PVA unaffected by subsequent incubations with antithrombin 111. PVA and heparin‐PVA presented a heterogeneous and complex substrate for interaction with proteins. The adsorbed protein was likely present in multiple states depending on the groups with which i

ISSN:0021-9304    

DOI:10.1002/jbm.820260709

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThere is a strong relationship between mechanical stress and calcification in biological prosthetic heart valves. A dynamicin vitrocalcification test has been used to study the relationship between stress distributions in the leaflets of bovine pericardial valves and the deposition of calcium over the leaflet surfaces. Intuitive stress regions have been defined over the leaflet surfaces. Calcium uptake by the leaflets has been assayed directly by ashing of leaflet material and analysis of the ash by atomic absorption spectrophotometry. Calcium and phosphorus distribution over the leaflet surface has been analyzed using energy‐dispersive x‐ray analysis by scanning electron microscope and data points assigned to the appropriate stress region. The uptake of calcium is assessed by comparing stress regions, surfaces, and the degree of calcification of the valve. Differences between stress regions and surfaces are significant. Uptake of calcium in these valves appears to be strongly related to the degree and type of stress present in the valve leafl

ISSN:0021-9304    

DOI:10.1002/jbm.820260710

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractIslets were encapsulated into 5% concentration agarose microbeads. The effect of microencapsulation on islet allograft survivals was determined using a streptozotocininduced diabetic (STZ) mouse and a nonobese diabetic (NOD) mouse as recipients. All five STZ BALB/c mice receiving microencapsulated islets (C57BL/6) maintained normoglycemia indefinitely. When NOD mice were used as recipients of the bioartificial pancreas, four of five grafts (islets from C3H/He) functioned for more than 80 d. Two of five NOD mice maintained normoglycemia until animals were sacrificed at 102 and 192 postoperative d. Microbeads made of commercially available agarose can effectively prolong alloislets functioning in the STZ‐diabetic mouse and even in the NOD mouse (animal model of human type I diabetes) without the use of any immunosuppressive dru

ISSN:0021-9304    

DOI:10.1002/jbm.820260711

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY