摘要:

This paper describes and evaluates a method for quantifying the amounts of specific plasma proteins adsorbed to biomaterial surfaces. In particular, it demonstrates that macroscopic images (`stains'), that assess the spatial distribution of albumin, IgG, fibrinogen, and HMK (high molecular weight kininogen), can be obtained over areas of at least 12 cm2using immunospecific adhesion of dyed polystyrene beads. Stain intensities, measured with a scanner and an image analysis system, were found to quantify the amount of specific protein in the solution used to coat the surfaces. Results obtained with the proposed method produced single protein isotherms for albumin, immunoglobulin G (IgG) and fibrinogen that followed Langmuir-like adsorption behavior and were similar to previously published isotherms. The HMK isotherm also exhibited Langmuir-like adsorption behavior. The proposed method also detected the presence of an expected maximum in the adsorption of fibrinogen onto glass as a function of plasma dilution. Adsorption of fibrinogen out of 6.4% plasma onto glass from a separated flow produced results indicating the quantity as well as the location of fibrinogen at the boundary of the separated region. This result confirmed the utility of the proposed method for detecting spatial distributions of specific proteins adsorbed from plasma in practical devices.

ISSN:0920-5063    

DOI:10.1163/156856297X00542

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Control over the adsorption of proteins and over the adsorption and spatial orientation of mammalian cells onto surfaces has been achieved by modification of glass and other silicon oxide substrates with poly(N-isopropylacrylamide) (PNIPAM). The functionalization of the substrates was achieved either by a polymer-analogous reaction of aminosilanes with reactive N-(isopropylacrylamide) (NIPAM)-copolymers and by copolymerization of NIPAM with surface-bound methacrylsilane. The obtained coatings were characterized by FT-IR, ellipsometry, and surface plasmon resonance measurements. The adsorption of two proteins-fibrinogen and ribonuclease A-on these surfaces was studied in situ by real time surface plasmon resonance measurements. The PNlPAM-grafted surfaces prepared by either chemical procedure inhibited the adsorption of both proteins. More importantly they prevented the adhesion of neuroblastomaXglioma hybrid cells cultured either in serum-free medium or in a medium containing serum proteins. Deep-UV irradiation was used to perform ablation processes and to create patterns permitting the examination of spatially controlled adhesion and growth of cells. This study showed that patterned ultrathin polymer films on glass are suitable substrates for controlling the interactions of cells with surfaces and are capable of directing the attachment and spreading of cells.

ISSN:0920-5063    

DOI:10.1163/156856297X00551

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Protein adsorption and complement activation were studied on thin evaporated films of titanium (Ti). The surfaces were cleaned in either a radio frequency (RF) plasma unit, or washed sequentially in trichloroethylene, acetone, ethanol, and water. Both methods resulted in hydrophilic surfaces with low carbon contamination on the outermost oxide ( ~ 11-13 at%). In situ ellipsometry suggested that Ti is an intrinsic coagulation activator in vitro, since significant amounts of factor XII (F XII) and high molecular weight kininogen (HMWK) were found on the surfaces after 1 min incubation in heparin plasma. Ellipsometry, performed after serum incubations ranging from 15 s to 30 min showed that the total amount of serum proteins and the deposition of antibodies to complement factor 3c (C3c) increased with serum incubation time. ELISA methods showed increased levels of free iC3b in serum after 10 min incubation of the surfaces, but no detectable amounts of C3 convertase fractions C4d or Bb. Ellipsometric results indicated, however, an increased deposition of antibodies to C I q and IgG on Ti after short serum incubation times. The combined results indicate that Ti-surfaces initially activate complement through the classical pathway. The activation then continues via a positive amplification loop where increased amounts of C3 are deposited on the surfaces via the alternative pathway.

ISSN:0920-5063    

DOI:10.1163/156856297X00560

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Protein adsorption, contact activation, and complement activation were studied on thin evaporated films of chromium (Cr) in vitro. The surfaces were, prior to the experiments, cleaned in either ethanol and water, or in a basic peroxide solution (RCA standard clean 1,SC-1 Surface spectroscopic studies of the outermost oxides showed a significant reduction of carbon contaminants after washing in SC-1 but also suggested an increase in the oxidation state as compared with the ethanol-washed surfaces. In situ ellipsometry combined with antibody techniques was used to determine protein deposition and antibody binding onto surfaces after incubations in heparin plasma or in normal serum. Incubation times from I to 10 min in serum showed increased depositions of serum and antibodies to complement factor 3c (C3c) and was larger on ethanol-washed surfaces than on surfaces washed in SC-1. ELISA methods indicated increased amounts of iC3b in serum for both surfaces, but no presence of C3 convertases (C4d or Bb fractions). A low or transient complement activation via the classical pathway was indicated on ethanol washed Cr, since deposition of secondary antibodies to complement factor Iq (Clq) was observed only after short incubation times in serum. No procoagulant activity of Cr was indicated, since only low amounts of antibodies to factor XII (F XII), prekallikrein (PKK), and high molecular weight kiniogen (HMWK) bound to the surfaces after incubations in heparin plasma. These results were confirmed using a colorimetric assay where the relative amounts of free plasma kallikrein was assessed using a chromogenic substrate, H-D-Pro-Phe-Arg-pNA (S-2302).

ISSN:0920-5063    

DOI:10.1163/156856297X00579

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Polylactic acid (PLA) is a bioresorbable polymer that is used in a number of clinical situations. Complex shapes of PLA are commonly machined for bone fixation and reconstruction. Solid free form fabrication methods, such as 3D printing, can produce complex-shaped articles directly from a CAD model. This study reports on the mechanical properties of 3D-printed PLLA parts. 3D printing is a solid free-form fabrication process which produces components by ink-jet printing a binder into sequential powder layers. Test bars were fabricated from low and high molecular weight PLA powders with chloroform used as a binder. The binder printed per unit line length of the powder was varied to analyze the effects of printing conditions on mechanical and physical properties of the PLA bars. Furthermore, cold isostatic pressing was performed after printing to improve the mechanical properties of the printed bars. The maximum measured tensile strength for the low molecular weight PLLA (53 000) is 17.40 ± 0.71 MPa and for high molecular weight PLLA (312 000) is 15.94 ± 1.50 MPa.

ISSN:0920-5063    

DOI:10.1163/156856297X00588

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor