SEARCH · PubMed Health

Results for “surface modification”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources

PubMed2000

Novel beta-emitting poly(ethylene terephthalate) surface modification.

Restenosis after percutaneous interventions in coronary and peripheral arteries leads to repeat procedures and surgery in a significant number of patients. We have previously demonstrated that irradiation of an arterial site using an endovascular source (brachytherapy) is highly effective in preventing the restenotic process. To this end, a novel beta radiation delivery system was developed, based on the adsorption of (32)P (o-phosphoric acid) by pH-sensitive chitosan hydrogel on a poly(ethylene terephthalate) (PET) balloon surface. The PET balloon surface was treated with oxygen plasma and coated with chitosan hydrogel. Covalent bonds, ionic bonds, and hydrogen bonds all contribute to the adhesion between chitosan hydrogel and PET. In the aqueous phosphoric acid (PA) solution, the -NH(2) groups of chitosan were protonated by PA and the adsorption of PA occurred at the same time. The effect of PA concentration and temperature on adsorption efficiency and kinetics were studied. More than 70% PA was adsorbed on the sample surface in 0.2 mM PA solution. The surface of samples was also investigated by attenuated total reflection-Fourier transform infrared spectroscopy and scanning electron microscopy. PET surface may be modified to carry high activity beta emitters; such materials may be useful in a therapeutic setting

Adsorption↗

PubMed2005

Inorganic materials and living organisms: surface modifications and fungal responses to various asbestos forms.

In a previous study several strains of soil fungi were reported to remove iron in vitro from crocidolite asbestos, a process that was envisaged as a possible bioremediation route for asbestos-polluted soils. Here, we get some new insight into the chemical basis of the fiber/fungi interaction by comparing the action of the most active fungal strain Fusarium oxysporum on three kind of asbestos fibers--chrysotile, amosite, and crocidolite--and on a surface-modified crocidolite. None of the fibers examined significantly inhibited biomass production. Even the smallest fibrils were visibly removed from the supernatant following adhesion to fungal hyphae. F. oxysporum, through release of chelators, extracted iron from all fibers; the higher the amount of iron at the exposed surface, the larger the amount removed, that is, crocidolite > amosite >> chrysotile. When considering the fraction of total iron extracted, however, the ranking was chrysotile > crocidolite > amosite > heated crocidolite, because of the different accessibility of the chelators to the metal ions in the crystal structure. Chrysotile was the easiest to deplete of its metal content. Iron removal fully blunted HO* radical release from crocidolite and chrysotile but only partially from amosite. The removal, in a long-term experiment, of more iron than is expected to be at the surface suggests a diffusion of ions from the bulk solid towards the surface depleted of iron by fungal activity. Thus, if the fibers could be treated with a continuous source of chelators, iron extraction would proceed up to a full inactivation of free radical release. The fungal metabolic response of F. oxysporum grown in the presence of chrysotile, amosite and crocidolite revealed that new extracellular proteins are induced--including manganese-superoxide dismutase, the typical antioxidant defense--and others are repressed, upon direct contact with the fibers. The protein profile induced by heated crocidolite was different, a result suggesting a key role for the state of the fiber/hyphae interface in protein induction.

Asbestos↗

PubMed2005

Electrode surface modification by a spirobifluorene derivative. An XPS and electrochemical investigation.

Ordered thin layers of a spirobifluorene derivative containing an amino group were formed by grafting them onto a self-assembled monolayer (SAM) of 11-mercaptoundecanoic acid (11-MUA) on gold. Either physical (H-bonding) or chemical bonding (activated by EDCl) was investigated. X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy confirmed that both methods can be used to effectively graft 2-amino-9,9'-spirobifluorene molecules onto the SAM surface, giving high surface coverages, with a significantly higher packing in the case of chemisorbed films. EIS measurements also showed that the covalently bonded spirobifluorene SAMs act as an effective barrier to both ion penetration and heterogeneous electron transfer.

Journal Article↗

PubMed2001

Titanium-porcelain system. Part III: effects of surface modification on bond strengths.

During its development, titanium was found to be incompatible with conventional dental porcelains due to weak bond strength brought about by titanium's high yet oxidative nature. In spite of the development of new low-fusing porcelains designed for titanium application, previous studies have shown that sandblasting pre-treatment prior to porcelain application led to weakening of the metal-ceramic bonding. The aim of this study is to search for an effective alternative to sandblasting for the surface treatment of the titanium substrate in the titanium-porcelain system. The research evaluated the bond strength of 165 samples of titanium-porcelain systems divided into 11 groups. A three-point flexural bend test was conducted to measure the force required to fracture the porcelain on the titanium substrate. A correlation between the type of surface treatment and the bond strengths of each group was evaluated if it resulted to significant differences. The study found significantly differences in the energy-to-break of titanium-porcelain systems treated with hydrochloric acid and sandblasting compared with the control group. The bonds strength achieved by the titanium-porcelain system when treated with hydrochloric acid is comparable to that of conventional metal-ceramic alloy system. Hydrochloric acid treatment of the titanium substrate is a promising alternative to sandblasting for the surface treatment of the titanium substrate in the titanium-porcelain system.

Aluminum Oxide↗

PubMed1991

Complement activation and bioincompatibility. The terminal complement complex for evaluation and surface modification with heparin for improvement of biomaterials.

The degree of biocompatibility of biomaterials can be evaluated using various assay systems detecting activation of the blood cascade systems, leukocytes or platelets. Activation of complement is one mechanism associated with adverse effects observed when bioincompatible materials are used. We present data showing that the terminal complement complex, an indicator of terminal pathway activation, is suitable for evaluation of biocompatibility of biomaterials such as cardiopulmonary bypass devices. Furthermore, our results suggest that bioincompatibility is improved when artificial surfaces are modified with end point attached functionally active heparin.

Complement Activation↗

PubMed1990

Surface modification of biomaterials through noble metal ion implantation.

Studies are described involving effects of noble-metal ion implantation on corrosion inhibition and charge-injection capabilities of surgical Ti-6A1-4V alloy. A major factor linked to excellent long-term biological performance is resistance to metal-ion release to tissues. The elements most resistant to corrosion in aqueous solutions are the noble metals. Disadvantages include expense and general inadequacy of mechanical properties. However, if small quantities can be used to surface-modify a surgical device in the last stage of manufacture, that device could possess an optimum combination of environmental integrity, biological response, mechanical properties, and charge-injection capability at minimum expense. Results for ion-implanted Ir are presented. Iridium has been described as the most corrosion-resistant element known, and its activated oxide as having the highest charge-injection capability of any material known. Ti-6A1-4V samples, ion implanted with 2.5 and 5.0 atomic % peak-maximum concentrations of Ir, were subjected to corrosion treatments to enrich the surface with Ir. Corrosion potential and cyclic voltammetry measurements indicated enrichment in H2SO4, and continued enrichment in isotonic saline, with corrosion potentials approaching that of pure Ir, and charge densities in isotonic saline exceeding that of pure Ir for the 5.0% peak-max Ir implanted material. X-ray photoelectron spectroscopy confirmed the high levels of Ir surface enrichment.

Alloys↗

PubMed1993

Surface modification of nanoparticles by PEO/PPO block copolymers to minimize interactions with blood components and prolong blood circulation in rats.

The biological fate of injected foreign particles is believed to be closely related to their interactions with blood plasma proteins and cells. In order to verify this correlation, we have quantitatively measured protein adsorption and blood retention profiles in rats by using model polystyrene latex nanoparticles. The in vitro interactions of these non-biodegradable particles with plasma proteins and whole blood can be altered by modifying their surfaces with a family of amphiphilic polymeric surfactants, PEO/PPO Pluronic or Tetronic block copolymers. Protein adsorption was measured by several techniques, including photon correlation spectroscopy, centrifugation, high performance liquid chromatography and field-flow fractionation. Pluronic F108 and Tetronic 908 and 1508 copolymers (with PEO terminal block MWPEO > 5000, PPO middle block MWPPO > 3000, and HLB values > 24) were shown to be the most effective surface modifiers in reducing adsorption of plasma proteins on the particles. Minimum interaction of coated particles with whole blood was also observed by optical microscopy. The blood circulation half-life of the particles injected in rats was increased from 20 min to 13 h when the latex particles (75 nm) were precoated with these block copolymers. These results suggest that nanoparticles designed for use as injectable drugs or drug carriers should display similar surface characteristics provided by such amphiphilic surface modifiers.

Adsorption↗

PubMed2003

Surface modification of hydroxyapatite. Part II. Silica.

Nanophase hydroxyapatite (HAP) particles were coated with varying amounts of silica (5-75wt%) via the hydrolysis of tetraethyl orthosilicate. The nanocomposite particles were characterized by transmission electron spectroscopy, X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), BET N(2) gas adsorption, sedimentation time studies, acid dissolution, and zeta potential (zeta). A sequential decrease in infrared spectral features characteristic of HAP was accompanied by an increase in features characteristic of silica as revealed by DRIFTS. The specific surface area of the silica-coated HAP particles showed a non-systematic increase. In comparison to the uncoated HAP (50m(2)/g), silica coatings of 5, 25, 50 and 75wt% yielded specific surface areas of 55, 93, 70, and 138m(2)/g, respectively. This behavior can be explained based on a heterocoagulation coating mechanism in which silica clusters of approximately 14nm in diameter adsorb onto the HAP particle surface. The decrease in specific surface area at 50wt% silica corresponded to the attainment of a complete surface coating. This conclusion was substantiated by the observed resistance of these particles to dissolution in 1M HCl. However, the acid treatment transformed the silica-coated HAP core particles to CaCl(2).Ca(H(2)PO(4))(2).2H(2)O (calcium chloride phosphate hydrate) based on XRD analysis.

Biocompatible Materials↗

PubMed1997

Heparin and heparin-surface-modification reduce Staphylococcus epidermidis adhesion to intraocular lenses.

Bacterial adherence to intraocular lenses (IOLs) could be the cause of endophthalmitis following cataract surgery and lens implantation. The majority of cases of postoperative endophthalmitis are caused by microflora that reside on or near the eye of the patient. Staphylococcus epidermidis commonly colonizes the eyelid margin and conjunctiva and is the most common organism causing postoperative endophthalmitis. In this study, the in vitro adherence of S. epidermidis to regular poly-methyl methacrylate (PMMA) IOLs and to heparin-surface-modified (HSM) PMMA IOLs was investigated. The effects of heparin and antibiotics in solution on the adherence of bacteria to regular PMMA IOLs were evaluated. Adhesion of bacterial cells to IOLs was determined by counting the viable cells attached to the lenses. Significantly, fewer S. epidermidis attached to HSM-PMMA IOLs and to regular PMMA IOLs treated with heparin than to PMMA IOLs (p < 0.001). Furthermore, bacteria attached in significantly lower numbers to regular PMMA IOLs treated with heparin than to HSM-PMMA IOLs (p = 0.0031). Antibiotics in solution had no significant effect on bacterial adherence to PMMA IOLs. These data indicate that the use of HSM-PMMA IOLs and treatment of PMMA IOLs with heparin could diminish the incidence of postoperative endophthalmitis and intraocular inflammation associated with IOL implantation.

Anti-Bacterial Agents↗

PubMed2005

Surface modification of crosslinked poly(styrene-divinyl benzene) micrometer-sized particles of narrow size distribution by ozonolysis.

Micrometer-sized polystyrene template particles of narrow size distribution were prepared by dispersion polymerization of styrene in 2-methoxyethanol. Uniform micrometer-sized polystyrene/crosslinked poly(styrene-divinyl benzene) composite particles were formed by a single-step swelling process of the template particles with styrene, divinyl benzene and benzoyl peroxide, followed by polymerization at 70 degrees C. Uniform micrometer-sized crosslinked poly(styrene-divinyl benzene) particles of higher surface area were produced by dissolution of the template polystyrene part of the former composite particles with N,N-dimethylformamide. Hydroperoxide conjugated crosslinked poly(styrene-divinyl benzene) particles were produced by ozonolysis of these particles. The effect of ozonolysis conditions, such as exposure time and flow rate of the ozone, on the hydroperoxide conjugation to the crosslinked particles was also studied. Functionalization of the crosslinked poly(styrene-divinyl benzene) particles was performed by graft polymerization of vinylic monomers such as acrylonitrile and chloromethylstyrene on the hydroperoxide conjugated crosslinked particles. This was accomplished by raising the temperature (e.g., 70 degrees C) of deairated acetonitrile dispersions containing the hydroperoxide conjugated particles and the vinylic monomers. The influence of various polymerization parameters on the grafting yield, e.g., monomer concentration, conjugated hydroperoxide concentration, and temperature, was also elucidated.

Journal Article↗

PubMed2003

Surface modification of TiO2 by a ruthenium(II) polypyridyl complex via silyl-linkage for the sensitized photocatalytic degradation of carbon tetrachloride by visible irradiation.

A new ruthenium(II) photosensitizer, [Ru(II)(py-pzH)(3)](2+) (where py-pzH=3-(2'-pyridyl)pyrazole), has been synthesized. The complex displayed outstanding excited state redox properties (estimated Ru(III)/Ru(II)* approximately -1.24 V vs. NHE) and was expected to sensitize the injection of electrons into the conduction band of anatase TiO(2) upon visible irradiation. The photosensitizer was anchored onto the surface of anatase TiO(2) particles via in situ silylation. The silyl-linkage displayed excellent stability in both aqueous media, over a wide pH range, and in common organic solvents. The resultant material, TiO(2)-[Ru(II)(py-pz-Si identical with )(3)], was found to be able to mediate degradation of CCl(4) in neutral aqueous medium under broad band visible irradiation (lambda>450 nm). The relation between the rate of degradation and concentration of substrate was explored and the mechanism of the photodegradation of the perhalogenated organic was discussed.

Carbon Tetrachloride↗

PubMed2006

Oxygen plasma surface modification enhances immobilization of simvastatin acid.

Simvastatin acid (SVA) has been reported to stimulate bone formation with increased expression of BMP-2. Therefore, immobilization of SVA onto dental implants is expected to promote osteogenesis at the bone tissue/implant interface. The aim of this study was to evaluate the immobilization behavior of SVA onto titanium (Ti), O(2)-plasma treated titanium (Ti + O(2)), thin-film coatings of hexamethyldisiloxane (HMDSO), and O(2)-plasma treated HMDSO (HMDSO + O(2)) by using the quartz crystal microbalance-dissipation (QCM-D) technique. HMDSO surfaces were activated by the introduction of an OH group and/or O(2)-functional groups by O(2)-plasma treatment. In contrast, titanium surfaces showed no appreciable compositional changes by O(2)-plasma treatment. The QCM-D technique enabled evaluation even at the adsorption behavior of a substance with a low molecular weight such as simvastatin. The largest amount of SVA was adsorbed on O(2)-plasma treated HMDSO surfaces compared to untreated titanium, HMDSO-coated titanium, and O(2)-plasma treated titanium. These findings suggested that the adsorption of SVA was enhanced on more hydrophilic surfaces concomitant with the presence of an OH group and/or O(2)-functional group resulting from the O(2)-plasma treatment, and that an organic film of HMDSO followed by O(2)-plasma treatment is a promising method for the adsorption of SVA in dental implant systems.

Adsorption↗

PubMed1986

Platelet-aggregating activities of metastasizing tumor cells. IV. Effects of cell surface modification on thrombin generation, platelet aggregation and subsequent lung colonization.

Platelet-aggregating and thrombin-generating activities of B16 and 3LL cells were inhibited by trypsin, phospholipase A2 and by heating, but not by neuraminidase. It was confirmed that the platelet aggregation effect of these cells is due to thrombin generation. The lung-colonizing ability of treated cells injected intravenously was directly proportional to the ability to generate thrombin and to aggregate platelets. These results suggest that B16 and 3LL cells aggregate platelets through thrombin generation probably via their heat-labile surface lipoprotein, and that emboli composed of platelets, fibrin, and tumor cells may aid further the metastatic process.

Animals↗

PubMed2005

Polysulfone-graft-poly(ethylene glycol) graft copolymers for surface modification of polysulfone membranes.

Amphiphilic graft copolymers having polysulfone (PSf) backbones and poly(ethylene glycol) (PEG) side chains were synthesized via reaction of an alkoxide formed from PEG and a base (sodium hydride) with chloromethylated polysulfone. The resulting polysulfone-graft-poly(ethylene glycol), PSf-g-PEG, materials were hydrophilic but water insoluble, rendering them potentially useful as biomaterial coatings. PSf-g-PEG films exhibited high resistance to protein adsorption and cell attachment. When used as an additive in PSf membranes prepared by immersion precipitation, the graft copolymer preferentially segregates to the membrane surface, delivering enhanced wettability, porosity and protein resistance compared to unmodified PSf membranes. The surface properties of PSf-g-PEG modified membranes render them desirable candidates for hemodialysis.

Animals↗

PubMed2000

Surface modification of poly(lactic acid) nanospheres using hydrophobically modified dextrans as stabilizers in an o/w emulsion/evaporation technique.

Sterically stabilized biocompatible poly(lactic acid) (PLA) nanospheres were prepared by an o/w emulsion/evaporation technique, using hydrophobically modified dextrans (DexP) as the emulsion stabilizer. Photon correlation spectroscopy, zetametry, and differential scanning calorimetry studies corroborated that interfacial adhesion between immiscible dextran and PLA chains was achieved by compatibilization of polymer segments via hydrophobic groups grafted onto dextran and thus leading to the formation of entanglements between the hydrophobic dextran parts and the PLA matrix. The presence of dextran exposed at the particle surface was confirmed by X-ray photoelectron spectroscopy and by the fact that the suspensions showed an increased stability in concentrated NaCl solutions and a reduction of bovine serum albumin adsorption compared to uncoated PLA nanoparticles. A comparison of the characteristics of PLA nanospheres DexP-coated via the emulsion procedure (NS(em)) with those of PLA particles coated by DexP adsorption (NS(ad)) suggests that the conformation of the polymer in the superficial layers may be different. However, both DexP layers behave similarly in terms of stability and protein adsorption.

Adsorption↗

PubMed1991

Impact of surface modifications of Acanthocheilonema viteae microfilariae on cell adhesion.

Exposure of A. viteae microfilariae to various lectins reduced their capacity to react with the peritoneal exudate cells of the host, Mastomys natalensis. Sugars corresponding to these lectins with the exception of N-acetyl glucosamine, did not affect the adhesion per se. They however, protected the parasite against the adverse effect of lectins. Neuraminidase and chitinase also suppressed adhesion capacity of the microfilariae. Except sodium dodecylsulphate which enhanced cell attachment, other surfactants inhibited this reaction considerably. The results indicate that antibody dependent adhesion of the microfilariae with the macrophages involves surface moieties of the parasite, where N-acetylglucosamine acts as the principal sugar residue. Participation of -SH groups also is inferred from the observations that p-chloromercuribenzoate and dithiobis-(2-nitrobenzoic acid) inhibited cell attachment and dithiothreitol provided protection against these agents.

Acetylgalactosamine↗

PubMed2004

Surface modifications of alumina-silica glass fiber.

A commercial glass fiber with Al(2)O(3) (68.4%) and SiO(2) (27.6%) as major components and CaO, TiO(2), Fe(2)O(3), and CuO as minor components was used as substrate in a silica sol-gel coating process. After cleaning, fiber samples were immersed into tetraethoxysilane (TEOS) at room temperature for 1 h, and then individual fiber samples were soaked into a simulated body fluid (SBF) solution,1 and removed after 5, 10, 15, and 20 days. Zeta potential and Energy Dispersive Spectroscopy (EDS) analyses showed that the fiber surfaces were effectively coated with a silica layer, which improved the formation of an HA layer upon immersion into SBF solution for 5 days. The coating became even more continuous after 10-day immersion. Fourier Transform Infrared Spectroscopic (FTIR) analyses confirmed that the coating layer has P--O vibration bands characteristic of hydroxyapatite (HA) near 1060 and 600 cm(-1).

Aluminum Oxide↗

PubMed2005

The role of implant surface modifications, shape and material on the success of osseointegrated dental implants. A Cochrane systematic review.

We tested the hypothesis of no difference in implant failures between various dental implant types. We searched for all randomised clinical trials comparing different implant types/systems with a follow up of at least one year on four databases. Screening of eligible trials, quality assessment and data extraction were conducted in duplicate. Thirty-one trials were identified. Twelve trials, reporting results of 512 patients, were included. No significant differences were observed for implant failures. There were minor statistically significant differences for peri-implant bone level changes. Turned surfaces had a 20% reduction in risk of being affected by perimplantitis over a 3-year period.

Dental Implantation, Endosseous↗