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Results for “surface modification”

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PubMed1998

Effects of amide and amine plasma-treated ePTFE vascular grafts on endothelial cell lining in an artificial circulatory system.

We sought to examine whether surface modification of expanded polytetrafluoroethylene (ePTFE) vascular grafts might extend graft patency without modifying the graft structure. Amide and amine plasma (butylamine) were applied to graft surfaces using radio frequency glow discharge. Surface analyses by Fourier transform infrared spectroscopy-attenuated total reflectance, X-ray photoelectron spectroscopy, and dynamic contact angle measurements revealed the presence of nitrogen-containing functional groups on the plasma modified graft surfaces, along with an increased surface hydrophilicity. Bovine aortic endothelial cells were seeded on amide and amine plasma coated ePTFE vascular grafts and placed inside an artificial circulatory system under well-defined flow conditions. The seeded endothelial cells were exposed to either constant or pulsatile flow condition for 5 days. Their corresponding maximum wall shear stresses were 1 dyn/cm2 under constant flow and 65, 108, and 259 dyn/cm2 under various pulsatile flows. Plasma modified ePTFE vascular grafts enhanced the endothelial cell lining under constant and pulsatile flow conditions. Fluorescence nuclear staining, scanning electron microscopy, and histological staining indicated the formation of an endothelial cell monolayer on the plasma coated graft surfaces.

Amides↗

PubMed1999

Surface micropatterning to regulate cell functions.

The current technology available for surface microfabrication with macromolecules to regulate cell functions is reviewed. Surface topology, and surface modification with hydrophilic or hydrophobic polymers, electrically charged polymers, stimuli-responsive macromolecules, polysaccharide, and proteins involving adhesion or growth factors are discussed. These surface-microfabricatec biomaterials had the ability to regulate cell functions such as proliferation, differentiation, and apoptosis.

Animals↗

PubMed2000

Use of plasma glow for surface-engineering biomolecules to enhance bloodcompatibility of Dacron and PTFE vascular prosthesis.

The search for a nonthrombogenic material having patency to be used for small diameter vascular graft applications continues to be a field of extensive investigation. The purpose of the present study was to examine whether surface modification of polytetra fluoroethylene (PTFE, Teflon) and polyethylene-terephthalate (Dacron) vascular grafts might extend graft biocompatibility without modifying the graft structure. A series of surface coatings were prepared by modifying the argon plasma-treated PTFE and Dacron grafts with collagen IV and laminin and subsequently immobilizing bioactive molecules like PGE1, heparin or phosphatidyl choline via the carbodiimide functionalities. Surface analysis by Fourier transform infrared spectroscopy-attenuated total reflectance revealed the presence of new functional groups on the modified graft surfaces. In vitro studies showed that fibrinogen adsorption and platelet adhesion on modified grafts were significantly reduced. This study proposes that surface grafting of matrix components (collagen-type IV and laminin) and subsequent immobilization of bioactive molecules (PGE1, heparin or phosphatidyl choline) changed the surface conditioning of vascular grafts and subsequently improved their biocompatibility. However, more detailed in vivo studies are needed to confirm these observations.

Biocompatible Materials↗

PubMedDate not supplied

Immobilization of galactose ligands on acrylic acid graft-copolymerized poly(ethylene terephthalate) film and its application to hepatocyte culture.

Surface modification of argon-plasma-pretreated poly(ethylene terephthalate) (PET) films via UV-induced graft copolymerization with acrylic acid (AAc) was carried out. Galactosylated surfaces were then obtained by coupling a galactose derivative (1-O-(6'-aminohexyl)-D-galactopyranoside) to the AAc graft chains with the aid of a water-soluble carbodiimide (WSC) and N-hydroxysulfosuccinimide (sulfo-NHS). The modified PET films were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and water contact-angle measurements. The galactosylated PET films were used as substrates for hepatocyte culture. The effects of surface carboxyl group concentration on the extent of galactose ligand immobilization, the extent of hepatocyte attachment, and the surface morphology were investigated. The amount of the galactose ligands immobilized on the PET surface increased with the AAc polymer graft concentration. AFM images revealed that the surface roughness of the PET film increased after graft copolymerization with AAc, but did not change appreciably with the subsequent immobilization of the galactose ligands. At the surface carboxyl group concentration of about 0.56 micromol/cm(2) or galactose ligand concentration of about 0.51 micromol/cm(2), the hepatocyte culture on the galactosylated surface exhibited the optimum concentration and physiological functions and formed aggregates or spheroids after just 1 day of culture. The albumin and urea synthesis functions of these hepatocytes were comparable to or higher than those of the hepatocytes cultured on the collagen-modified PET substrates.

Acrylates↗

PubMed2004

Oriented attachment and membrane reconstitution of His-tagged cytochrome c oxidase to a gold electrode: in situ monitoring by surface-enhanced infrared absorption spectroscopy.

A novel concept is introduced for the oriented incorporation of membrane proteins into solid supported lipid bilayers. Recombinant cytochrome c oxidase solubilized in detergent was immobilized on a chemically modified gold surface via the affinity of its histidine-tag to a nickel-chelating nitrilo-triacetic acid (NTA) surface. The oriented protein monolayer was reconstituted into the lipid environment by detergent substitution. The individual steps of the surface modification, including (1) chemical modification of the gold support, (2) adsorption of the protein, and (3) reconstitution of the lipid bilayer, were followed in situ by means of surface-enhanced infrared absorption spectroscopy (SEIRAS) and accompanied by normal-mode analysis. The high surface sensitivity of SEIRAS allows for the identification of each chemical reaction process within the monolayer at the molecular level. Finally, full functionality of the surface-tethered cytochrome c oxidase was demonstrated by cyclic voltammetry after binding of the natural electron donor cytochrome c.

Electrochemistry↗

PubMed2005

Controlled grafting of comb copolymer brushes on poly(tetrafluoroethylene) films by surface-initiated living radical polymerizations.

Surface modification of poly(tetrafluoroethylene) (PTFE) films by well-defined comb copolymer brushes was carried out. Peroxide initiators were generated directly on the PTFE film surface via radio frequency Ar plasma pretreatment, followed by air exposure. Poly(glycidyl methacrylate) (PGMA) brushes were first prepared by surface-initiated reversible addition-fragmentation chain transfer polymerization from the peroxide initiators on the PTFE surface in the presence of a chain transfer agent. Kinetics study revealed a linear increase in the graft concentration of PGMA with the reaction time, indicating that the chain growth from the surface was consistent with a "controlled" or "living" process. alpha-Bromoester moieties were attached to the grafted PGMA by reaction of the epoxide groups with 2-bromo-2-methylpropionic acid. The comb copolymer brushes were subsequently prepared via surface-initiated atom transfer radical polymerization of two hydrophilic vinyl monomers, including poly(ethylene glycol) methyl ether methacrylate and sodium salt of 4-styrenesulfonic acid. The chemical composition of the modified PTFE surfaces was characterized by X-ray photoelectron spectroscopy.

Chromatography, High Pressure Liquid↗

PubMed2004

Easy and efficient bonding of biomolecules to an oxide surface of silicon.

A new method is described to attach biological molecules to the surface of silicon. Semiconductors such as Si modified with surface-bound capture molecules have enormous potential for use in biosensors for which an ideal detection platform should be inexpensive, recognize targets rapidly with high sensitivity and specificity, and possess superior stability. In this process, a self-assembled film of an organophosphonic acid is bonded to the native or synthesized oxide-coated Si surface as a film of the correspondingphosphonate. The phosphonate film is functionalized to enable covalently coupling biological molecules, ranging in size from small peptides to large multi-subunit proteins, to the Si surface. Surface modification and biomolecule coupling procedures are easily accomplished: all reactions can proceed in air, and most take place under ambient conditions. The biomolecule-modified surfaces are stable under physiological conditions, are selective for adhesion of specific cells types, and are reusable.

Animals↗

PubMed2005

Activated surfaces for laser desorption mass spectrometry: application for peptide and protein analysis.

Thanks to the development of matrix assisted laser desorption/ionisation (MALDI), laser desorption based mass spectrometry became an essential method for the analysis of biomolecules. This review will discuss the various surface modifications used in combination with laser desorption mass spectrometry and their application for the analysis of peptides and proteins. In the first hand, some modified surfaces are designed to enhance the laser desorption/ionisation process; this includes the use of carbon, porous silicon surfaces and also immobilised matrix. In an other hand chemical and biochemical modified surfaces developed to isolate species with more or less specific interactions can be used for on-slide sample clean-up before MALDI-MS analysis. In addition, different experimental devices as mass spectrometers and microfluidic devices used for such a purpose will be presented.

Animals↗

PubMed2003

[The research of using TiN nanometer film to improve the anticorrosive property of FeCrMo alloy].

OBJECTIVE: The aim of the study is to improve the anticorrosive property of the dental FeCrMo soft magnetic alloy covered with TiN film obtained by ion beam assisted deposition (IBAD) technology in oral environment. METHODS: The magnetic force of the FECrMo soft magnetic alloy after TiN film treated were measured by Instron test machine. An advanced electro-chemical method was used to measure the electric potential of corrosion (Ecorr), passive potential (Ep), passive current density (Ip), current density of corrosion (Icorr), polarization resistance (Rp), of FeCrMo soft magnetic alloy in simulated oral environment before and after surface modification. RESULTS: There were no statistic changes of the magnetic force in 4 groups after alloy with TiN film treated. Comparing with the alloy without surface modified, the Ecorr, Rp of FeCrMo soft magnetic alloy was obviously higher, and the Icorr, Ip and Ep were obviously lower. CONCLUSIONS: The anticorrosive property of the dental FeCrMo soft magnetic alloy with TiN film is better than that without modified.

Chromium Alloys↗

PubMed1994

Effect of plasma treatment on tribological properties of synthetic ligaments.

The objective of this study was to determine the optimal experimental conditions for plasma treatment of polyester ligaments. Two different surface modification techniques were used: tetrafluoroethylene and methane. Gas flow rate, pressure, power, and treatment period giving a thin film with low friction coefficient and low surface energy was determined. Control and plasma treated surfaces were characterized by X-ray photoelectron spectroscopy to investigate the functionalization of the treated surfaces in detail. The surface tension of control and plasma treated surfaces were determined from contact angle measurements to understand the adhesion and reactivity of films with aqueous medium. The results showed a decrease in friction coefficient from 0.45 to 0.28 and from 0.45 to 0.26 for thin films deposited respectively by tetrafluoroethylene (TFE) and methane (CH4) plasma. Contact angles increased from 63 degrees to 120 degrees for TFE plasma and from 63 degrees to 93 degrees for CH4 plasma. Large contact angles mean a weak affinity between molecules in water/material phase, so that the power to attract cells to the surface of the material is too weak. The results showed that optimal film, i.e., low static friction coefficient and large contact angle, can be obtained by a CH4 plasma treatment at high power RF. For TFE plasma treatments, a low power RF is needed to obtain a thin film with a stable chemical structure.

Adhesiveness↗

PubMed1995

[Alterations of heparin coating on intraocular lenses caused by implantation instruments].

BACKGROUND: In the last years heparin surface-modified intraocular lenses (HSM IOLs) were used for special indications like uveitis, synechia, congenital cataract or pseudoexfoliation syndrome. A monolayer of heparin molecules on the surface of PMMA-IOLs causes a reduced postoperative inflammatory reaction and produces a higher long-term biocompatibility than PMMA-IOLs without surface-modification. The study was designed to evaluate the possible damage of this heparin-monolayer on the PMMA-IOL by different metallic implantation forceps and different grasp-pressure. MATERIALS AND METHODS: Different implantation instruments were used to grasp HSM and conventional PMMA-IOLS. We designed a new device to generate and measure the pressure by the implantation forceps on the IOL in online-mode. After staining the heparin-monolayer with toluidin blue the surface alterations on the intraocular lenses were examined for surface alterations, especially of the heparin-monolayer, by light and scanning electron microscopy subsequently. RESULTS: Implant forceps produced defects of the heparin layer and the PMMA-material. Each implantation forceps induced a specific pattern of destructed heparin surface in the grasp area. These defects showed high correlation with the pressure and the morphology of the forceps as shown by light and scanning electron microscopy. CONCLUSIONS: Mechanical irritation during the implantation procedure destroyed the heparin layer on PMMA-IOLs in the grasp-area. Clinical consequences are not yet known, but possible. An instrument with rounded, soft and smooth grasp-surface is required for implantation of HSM IOLs to avoid surface alterations, so that the patients get maximum profit by the heparin-modification.

Cataract Extraction↗

PubMed2001

Cell adhesion peptide modification of gold-coated polyurethanes for vascular endothelial cell adhesion.

Gold-coated polyurethanes were chemisorbed with three cell-adhesion peptides having an N-terminal cysteine: cys-arg-gly-asp (CRGD), cys-arg-glu-asp-val (CREDV), and the cyclic peptide cys-cys-arg-arg-gly-asp-try-leu-cys (CCRRGDWLC). The peptides were selected based on their presumed preferential interactions with the cell-surface integrins on vascular endothelial cells. The ability of the surfaces to support the preferential adhesion of human vascular endothelial cells was studied by comparing in vitro adhesion results for these cells with those from mouse 3T3 fibroblasts. Surface modification with the peptides was confirmed by water-contact angles and XPS. Surface morphology was determined by AFM and SEM. In vitro cell-culture studies in conjunction with plasma-protein adsorption and immunoblotting were performed on the various modified surfaces. The data suggest that peptide-modified surfaces have significant potential for supporting cell adhesion. Little or no cell adhesion was noted on gold- or cysteine-modified control surfaces. Human vascular endothelial cells showed the greatest adhesion to the CCRRGDWLC-modified surfaces, and the 3T3 fibroblasts adhered best to the CREDV-modified surfaces. Protein adsorption studies suggest that the preferential adsorption of the cell-adhesive proteins fibronectin and vitronectin is not likely mediating the differences noted. It is concluded that the cell-adhesive peptide-modified gold-coated polymers have significant potential for further development both as model substrates for fundamental studies and for use in biomaterials applications.

3T3 Cells↗

PubMed2000

Microfabricated elastomeric stencils for micropatterning cell cultures.

Here we present an inexpensive method to fabricate microscopic cellular cultures, which does not require any surface modification of the substrate prior to cell seeding. The method utilizes a reusable elastomeric stencil (i.e., a membrane containing thru holes) which seals spontaneously against the surface. The stencil is applied to the cell-culture substrate before seeding. During seeding, the stencil prevents the substrate from being exposed to the cell suspension except on the hole areas. After cells are allowed to attach and the stencil is peeled off, cellular islands with a shape similar to the holes remain on the cell-culture substrate. This solvent-free method can be combined with a wide range of substrates (including biocompatible polymers, homogeneous or nonplanar surfaces, microelectronic chips, and gels), biomolecules, and virtually any adherent cell type.

Animals↗

PubMed2002

Osteoblast culture on polished titanium disks modified with phosphonic acids.

Titanium is widely used in dental implants due to its suitable physical properties and its good biocompatibility. However, it is integrated into bone only passively, and the resulting fixation in the bone, which is necessary for the function, is mainly mechanical in nature. With the objective of increasing the chemical interaction between the implant and the bone tissue, several phosphonic acids were synthesized and grafted onto titanium disks. Here we report on the proliferation, differentiation, and protein production of rat osteoblastic cells (CRP10/30) on phosphonic-acid-modified titanium surfaces studied in vitro. No statistical differences were found in osteoblast proliferation among the phosphonic-acid-modified titanium, unmodified titanium, and tissue culture plastic (used as a positive control), indicating that the phosphonic acids used were not cytotoxic to the osteoblasts used. For all surfaces (modified or not), the alkaline phosphatase activity was at least as good as it was on tissue culture plastic. However, the total amount of protein, and especially the collagen type I synthesis, was sensitive to surface modification. On titanium modified with ethane-1,1,2-triphosphonic acid, the total amount of synthesized protein was significantly higher than it was on unmodified titanium surfaces. A significant increase (up to 16%) of collagen type I production was observed on titanium surfaces modified with this acid or with methylenediphosphonic acid compared to unmodified titanium surfaces.

Alkaline Phosphatase↗

PubMed1990

Spectroscopic characterization of polyethyleneglycol modified superoxide dismutase: 1H NMR studies on its Cu2Co2 derivative.

Spectroscopic methods have been employed in order to understand the molecular basis of the decrease in enzymatic activity of the antiinflammatory enzyme copper-zinc superoxide dismutase (SOD) following the covalent binding of polyethyleneglycol (PEG) chains to the protein amino-groups. The PEG modification is a general method recently proposed to improve the therapeutic index of enzymes. 1H NMR spectra on the cobalt substituted PEG-modified SOD, Cu2Co2-PEG-SOD, have been recorded. The signals are quite broad with respect to the unmodified enzyme. This has been interpreted on the basis of the effect of molecular weight on the linewidth. The analysis has shown that the histidine hydrogens involved in metal binding at the enzyme active site are the same in both native and PEG-modified SOD. Similarly, circular dichroism and absorption spectra indicate that the overall conformation of the metal clusters is not perturbed upon modification. On the other hand, azide titration shows that the affinity constant of N-3 for SOD is largely reduced upon PEG modification (K = 154 M-1 and 75 M-1 for the native and modified SOD, respectively). These results indicate that the decrease in enzymatic activity upon surface modification with PEG is not caused by a perturbation of the active site geometry, but to a decrease in the channeling of the O2- ion towards the enzyme active site.

Circular Dichroism↗

PubMed2005

Micropatterning of polystyrene nanoparticles and its bioapplications.

Micropatterning of biomolecules forms the basis of cell culture, biosensor and microarray technology. Currently, the most widely used techniques are photoresist lithography, soft lithography or using robots which all involve multi-step surface modification directly on a planar substrate. Here we report a method to pattern biomolecules through self-assembling polystyrene nanoparticles in arrayed microwells on a solid surface to form well-ordered patterning, followed by attaching biomolecules to the assembled nanoparticles. The formation of colloidal patterns depends on capillary force, surface wettability and physical confinement. This method can be used for micropatterning a variety of biomolecules such as protein and antibody.

Colloids↗

PubMed2003

Development of an "electroptode" immunosensor: indium tin oxide-coated optical fiber tips conjugated with an electropolymerized thin film with conjugated cholera toxin B subunit.

We demonstrate that it is possible to create surface-conductive fiber optics, upon which may be electropolymerized a biotinylated polypyrrole thin film, which may then be used to affinity coat the fiber with molecular recognition probes. This fiber-optic electroconductive surface modification is done by the deposition of a thin layer of indium tin oxide. Thereafter, biotin-pyrrole monomers are electropolymerized onto the conductive metal oxide surface and then exposed to avidin. Avidin-biotin interactions were used to modify the fiber optics with biotin-conjugated cholera toxin B subunit molecules, for the construction of an immunosensor to detect cholera antitoxin antibodies. The biosensor was tested for sensitivity, nonspecificity, and overall practicality.

Antibodies↗

PubMed2000

Ongoing innovations in biomechanics and materials for the new millennium.

Material innovations are reviewed within the context of ongoing biomechanical developments that relate the critical contact angle of second-order angulation (theta c) to the overall resistance to sliding (RS). As a science in its embryonic stage of development, RS is partitioned into classical friction (FR), elastic binding (BI), and physical notching (NO). Both FR and BI are defined in terms of normal forces (N) and kinetic coefficients (mu k). The angulation at which NO occurs (theta z) is introduced as a second boundary condition to theta c. Given this scientific backdrop, material modifications are sought that reduce RS. Approaches include minimizing mu k or N within the context of FR and theta < theta c, as, for example, by surface modifications of arch wires and brackets or by engineering novel ligation materials. Stabilizing theta at theta approximately equal theta c should provide more efficient and effective sliding mechanics by developing innovative materials (eg, composites) in which stiffness (EI) varies without changing wire or bracket dimensions. Between the boundaries of theta c and theta z (ie, theta c < theta < theta z), BI may be reduced by decreasing EI or increasing interbracket distance (IBD), independent of whether a conventional or composite material is used.

Biomechanical Phenomena↗