摘要:

The relationships among surface, bulk properties and lipid sorption behaviors of segmented polyurethanes (SPUs) with various polyol soft segments were investigated. The polyols used in this study were poly(ethylene oxide) (PEO), poly(tetramethylene oxide) (PTMO), and poly(dimethylsiloxane) (PDMS). The hard segment of these segmented polyurethanes was composed of 4,4'-diphenylmethane diisocyanate and 1,4-butanediol, present at 50 wt %. X-ray photoelectron spectroscopic (XPS) and dynamic contact angle measurements were carried out in order to analyze the surface chemical structure in the air- and water-equilibrated states. XPS revealed that in the air-equilibrated state, lower surface free energy components were enriched at the air-solid interface, whereas in the water-equilibrated state, higher surface free energy components were enriched at the water-solid interface. The change in environment from air to water induced the surface reorganization in order to minimize interfacial free energy. Lipid sorption behaviors of SPUs were investigated by means of infrared spectroscopy. Even after extensive rinsing of the surface, the amount of lipid present on the SPU surface was more than that calculated on the assumption that a monolayer covers the SPU surface. Therefore, the lipid was not only adsorbed on the surface of SPU but absorbed into SPU. The SPU with hydrophilic PEO sorbed larger amount of phospholipid compared with that with hydrophobic polyol such as PTMO and PDMS. Also, the competitive sorption behaviors of phospholipid and cholesterol from their mixed liposome solution were studied. The ratio of sorbed cholesterol to phospholipid increased with an increase in surface hydrophobicity owing to the hydrophobic nature of cholesterol.

ISSN:0920-5063    

DOI:10.1163/156856293X00285

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Microencapsulated islets of Langerhans have been proposed as a bioartificial pancreas. However, foreign body reaction with fibrosis has been observed around implanted microcapsules. Since macrophages are present in this reaction and interleukin-1 (IL-1), a cytokine released by activated macrophages, may induce fibrosis, we tested the capacity of alginate-polylysine microcapsules to activate macrophages. Human monocytes were isolated from whole blood of healthy donors by a Ficoll density gradient and adherence to a plastic support. Monocytes were cultured for 24 h with: (1) alginate-polylysine microcapsules; (2) lipopolysaccharide (LPS) (positive control group); and (3) alone (negative control group). Monocyte activation was evaluated by measuring the secretion of IL-1β and the production of intracellular IL-1α and IL-1β. Macrophages characterization was performed by immunocytological subtyping. IL-1β release and intracellular IL-1β and IL-1β production were significantly higher when macrophages were cultured with alginate-polylysine microcapsules than when macrophages were cultured alone. In conclusion, macrophages are activated in vitro by alginate-polylysine microcapsules. This effect may be involved in the fibrosis observed in vivo around implanted microcapsules. In addition, interleukin-1, released during macrophage activation, may cross the microcapsule membrane and impair islet function.

ISSN:0920-5063    

DOI:10.1163/156856293X00294

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A PHEMA grafted polymer film was prepared by plasma induced graft copolymerization onto an elastic material, silicone rubber. The control, Ar plasma-treated, and PHEMA-grafted silicone rubber surfaces were characterized by ESCA, FTIR-ATR, and SEM techniques. ESCA verified the respective chemical shift of control and Ar plasma-treated films. The presence of the grafted PHEMA was also verified by ESCA. The amounts of grafted PHEMA did not monotonously increase with the plasma exposure conditions, but decreased after passing a maximum. The introduction of PHEMA onto a hydrophobic support provided an adequate surface for rabbit corneal epithelium cell attachment and growth. Cell attachment and growth onto these surfaces were examined by light microscopy. Cell attachment onto the control and Ar plasma-treated surface was negligible, while improved attachment and growth of rabbit corneal epithelium cells was demonstrated on the PHEMA-grafted polymer surface. The PHEMA-grafted silicone rubber surface demonstrated a confluent cell layer after 72 h.

ISSN:0920-5063    

DOI:10.1163/156856293X00302

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Undecalcified specimens of cemented arthroplasties obtained during the early and late phases were studied. On the tenth postoperative day, there was excellent interlocking of the cement with the soft and hard tissues of the bone: there was no necrosis of the bed of the implant: a neutrophilic and macrophagic inflammatory response, where present, was mild and focal. Samples of the bone-cement interface of well fixed components obtained (at autopsy or by biopsy) many years after implantation revealed a thin and quiescent fibrous interfacial membrane alternating with bone and osteoid (that is, segmental osseointegration) or a cartilaginous layer abutting on the cement. It is concluded that, firstly, modern cementation techniques are not associated with extensive necrosis of the underlying bone in the immediate postoperative period; secondly, monomeric and polymeric methylmethacrylate as such is not toxic to the tissues; and, thirdly, acrylic cement is osseointegrated when motion at the interface is at its minimum.

ISSN:0920-5063    

DOI:10.1163/156856293X00311

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Poly(etherurethane urea) (PEUU) elastomers when employed as biomedical devices may be susceptible to extraction upon implantation. Four PEUU elastomers containing a single PEUU formulation, but varying in terms of their additives, were subjected to an in vitro extraction procedure. The additives in the PEUUs were Methacrol® 2138 F at 5 wt% and Santowhite® powder at 1 wt % levels. Only 1-2 wt % of the PEUUs was extractable with methanol. Fourier transform infrared spectroscopy (FT-IR) furnished qualitative and quantitative information on the extractables. The extractables consisted of a PEUU component that on the average was richer in soft segment than the bulk PEUU, and the two additives, Methacrol® 2138 F and Santowhite®powder.

ISSN:0920-5063    

DOI:10.1163/156856293X00320

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Cell culture studies have often been used in the determination of the suitability of biomaterials as surfaces for the attachment and growth of cells. For such studies of surfaces for potential use in bone implants, cells derived from bone may be maintained in culture on tissue culture polystyrene (TCPS). We have determined the contribution that serum fibronectin (FN) or vitronectin (VN) make to the attachment and spreading of cells cultured from explanted human bone (bone-derived cells) during the first 90 min following seeding on culture surfaces. The attachment of bone-derived cells to TCPS was simulated two-fold by the addition of 10% (v/v) fetal bovine serum (FBS) to the seeding culture medium. The roles of FN and VN were determined by selective removal of the FN or VN from the FBS prior to addition to the culture medium. FBS from which the VN had been removed did not have this stimulatory activity. In contrast, the attachment of bone-derived cells onto TCPS from medium containing FN-depleted serum (which contained VN) was the same as when intact FBS was used. There was incomplete attachment of bone-derived cells (27% of cells) when seeded in medium containing FBS depleted of both VN and FN. Our results show that for human bone-derived cells, the attachment onto TCPS of cells planted in medium containing FBS during the first 90 min of culture is principally as a result of adsorption onto the surface of serum VN. As unmodified polystyrene (PS) has also been used previously as a model biomaterial surface, PS was compared to TCPS for attachment of the bone-derived cells. Attachment of bone-derived cells to TCPS was twice that onto PS, both when the medium was serum-free and when it contained FBS. Bone-derived cells attached to TCPS or PS onto which purified VN or FN had been precoated, with VN adsorbed onto PS being as effective as was VN adsorbed onto TCPS. With FN, there was an effect of the polystyrene surface chemistry which was evident in that suboptimal concentrations of FN had a slightly higher potency when adsorbed onto TCPS than did the same concentrations of FN coated onto PS. When preadsorbed onto TCPS, the potency of FN for attachment of bone-derived cells was at least equal to that of VN.

ISSN:0920-5063    

DOI:10.1163/156856293X00339

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The effects of sulfated polysaccharides on hepatocyte adhesion on the polystyrene dish and fibronectin-coated dish were investigated. Dextran sulfate and synthetic mannopyranan sulfate slightly inhibited hepatocyte adhesion on fibronectin-coated dish, while heparin showed no effect. On the other hand, hepatocyte adhesion on polystyrene dishes was stimulated in the presence of sulfated polysaccharides in the medium.

ISSN:0920-5063    

DOI:10.1163/156856293X00348

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor