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 1,369 records · Page 76Linked to original sources

PubMed2003

Corrosion and wear-corrosion behavior of NiTi modified by plasma source ion implantation.

The understanding of corrosion behavior in NiTi is critical for the devices using this shape-memory alloy. In order to improve the surface properties of NiTi such as corrosion resistance, plasma source ion implantation (PSII) technique was employed with oxygen as incident ions at three levels of implantation dose (5x10(16), 1x10(17) and 3x10(17) ions/cm(-2)). Pitting corrosion and wear-corrosion behavior of control and PSII-modified Ti-50.7at% Ni alloy were evaluated by cyclic potentiodynamic polarization and wear-corrosion measurements. Surface characterization was used to interpret the different corrosion behavior observed between control and oxygen-implanted samples. Results showed that corrosion behavior was influenced by both heat treatment and surface modification. The best pitting corrosion resistance was observed for samples with Af=21 degrees C modified by oxygen implantation at a dose of 1x10(17) ions/cm(-2). Better wear-corrosion resistance was observed for oxygen-implanted samples.

Biocompatible Materials↗

PubMed2006

Electrochemical template synthesis of multisegment nanowires: fabrication and protein functionalization.

Multisegment nanowires represent a unique platform for engineering multifunctional nanoparticles for a wide range of applications. For example, the optical and magnetic properties of nanowires can be tailored by modifying the size, shape, and composition of each segment. Similarly, surface modification can be used to tailor chemical and biological properties. In this article, we report on recent work on electrochemical template synthesis of nanogap electrodes, the fabrication of multisegment nanowires with embedded catalysts, and the selective functionalization of multisegment nanowires with proteins.

Catalysis↗

PubMed1975

[Surface changes at the stage of fusion of the palatal ridges: light and scanning electron microscope study].

Surface modifications appear prior to the joining stage of the palatal shelves. They take the same appearance in vivo and in vitro: cell agglutination, nuclear hypertrophy, exfoliation and release of cellular material, formation of uniting bridges across the gap between the shelves.

Animals↗

PubMed2000

Glutardialdehyde induced fluorescence technique (GIFT): a new method for the imaging of platelet adhesion on biomaterials.

One of the major limitations of biomaterials used in medicine is the adhesion and subsequent activation of platelets upon contact with blood. The development of new or modified materials necessitates adequate methods for the detection and quantification of platelet/material interactions. These interactions are commonly investigated by means of scanning electron microscopy (SEM), radioisotope and immunological techniques, or by quantification of released platelet contents. Given the lack of a simple, rapid, and inexpensive assay, we developed a novel method for the accurate assessment of platelet adhesion after contact with foreign surfaces, which enables quantitative measurements as well as imaging of the platelet shape change, and which omits conventional or immunological staining and time-consuming preparative steps. The glutardialdehyde induced fluorescence technique (GIFT) uses the epifluorescence of glutardialdehyde-fixed platelets detected by fluorescence microscopy and is suitable for opaque and transparent materials. Combined with computer-aided image analysis, numbers of adherent platelets, platelet-covered surface, and average platelet spread area can be determined as markers of surface thrombogenicity. To validate the technique, four materials of different thrombogenicity [polypropylene (PP), poly(D,L-lactide) (PDLLA), 2-hydroxyethyl-methacrylate-grafted PDLLA (PDLLA-HEMA), and heparin-coupled PDLLA-HEMA] were investigated by GIFT and SEM. We found concordant results with SEM and GIFT with the following ranking of thrombogenicity: PP > PDLLA > PDLLA-HEMA > or = PDLLA-HEMA-heparin. GIFT significantly discriminated between the investigated materials. The surface modifications led to improved thromboresistance with reduced platelet adhesion and shape change. The main advantages of GIFT as compared with SEM are: no vacuum-drying or dehydration, less time-consuming procedure, fixation and fluorescence "staining" in one step, and suitability for computer-aided image analysis allowing quantitative assessment of platelet adhesion as well as imaging of the platelet shape change with high-contrast images. In conclusion, GIFT is a valid, rapid, and simple method for the quantitative determination of platelet/material interactions intended for the evaluation of thrombogenicity of biomaterials surfaces.

Biocompatible Materials↗

PubMedDate not supplied

Neoendothelial healing of modified EPTFE grafts.

Expanded polytetrafluoroethylene (EPTFE) grafts have poor neoendothelial healing characteristics and low patency rates after long-term implantation. The authors have shown that this is due to the low porosity of currently used EPTFE grafts (20-30 microns fibril length). The inner surface coated grafts made of long antithrombogenic material fibrils (40-60 microns) are desirable, especially for small diameter grafts. The authors have implanted these surface modified grafts (coated grafts) and noncoated grafts into abdominal arteries of rats and observed good patency rates, and the effects of surface modification of the grafts on stable endothelial tissue growth. The authors used four different kinds of grafts (fibril length, 20, 40, 60, and 90 microns, respectively) to investigate the effect of porosity. High porosity (long fibril length) grafts induce good neoendothelial healing and collagen production.

Animals↗

PubMed2006

Synthesis of biocompatible hydrophobic silica-gelatin nano-hybrid by sol-gel process.

Silica-biopolymer hybrid has been synthesised using colloidal silica as the precursor for silica and gelatin as the biopolymer counterpart. The surface modification of the hybrid material has been done with methyltrimethoxysilane leading to the formation of biocompatible hydrophobic silica-gelatin hybrid. Here we are reporting hydrophobic silica-gelatin hybrid and coating precursor for the first time. The hybrid gel has been evaluated for chemical modification, thermal degradation, hydrophobicity, particle size, transparency under the UV-visible region and morphology. FTIR spectroscopy has been used to verify the presence of CH(3) groups which introduce hydrophobicity to the SiO2-MTMS-gelatin hybrids. The hydrophobic property has also been tailored by varying the concentration of methyltrimethoxysilane. Contact angle by Wilhelmy plate method of transparent hydrophobic silica-gelatin coatings has been found to be as high as approximately 95 degrees . Oxidation of the organic group which induces the hydrophobic character occurs at 530 degrees C which indicates that the surface hydrophobicity is retained up to that temperature. Optical transmittance of SiO2-MTMS-gelatin hybrid coatings on glass substrates has been found to be close to 100% which will enable the hybrid for possible optical applications and also for preparation of transparent biocompatible hydrophobic coatings on biological substrates such as leather.

Coated Materials, Biocompatible↗

PubMed2006

Active oxygen processing for acrylic intraocular lenses to prevent posterior capsule opacification.

PURPOSE: To evaluate active oxygen processing on the surface of acrylic intraocular lenses (IOLs) to prevent secondary posterior capsule opacification (PCO). SETTING: Department of Ophthalmology, Dokkyo Medical University School of Medicine, Mibu City, Tochigi, Japan. METHODS: Acrylic IOLs were prepared, and ultraviolet (UV)/ozone (UV/O3) or argon plasma was irradiated to the surface of the IOLs. Elemental analysis (electron spectroscopy for chemical analysis [ESCA]) of the IOL surfaces was performed to confirm surface modification. Changes produced by UV/O3 or argon plasma treatment were examined for fibronectin and lens epithelial cell (LEC) adhesion. To evaluate the PCO prevention by treated IOLs, 8-week-old albino rabbits were used. The rabbit eyes randomly had phacoemulcification and implantation of 3 different IOLs: the UV/O3-treated IOLs, argon plasma-treated IOLs, and the control IOLs. After 2 weeks, the rabbits were killed and their globes were dissected and fixed using formaldehyde 10%. The PCO was observed using light microscopy (DX51, ORIMPUS) after hematoxylin and eosin staining. RESULTS: Comparison of IOL surface composition by ESCA showed an increase in nitrogen content and hydroxyl substitute and carboxyl substitute groups on surfaces of treated IOLs. The fibronectin adhesion and the LEC adhesion on the UV/O3-treated and argon plasma-treated samples were increased. In the untreated group, there was statistically significant inhibition of PCO formation in the UV/O3-treated and argon plasma-treated groups. CONCLUSION: Active oxygen processing and argon plasma irradiation on the surface of IOLs was effective in preventing secondary PCO after cataract surgery.

Acrylic Resins↗

PubMed2004

Silk fibroin modified porous poly(epsilon-caprolactone) scaffold for human fibroblast culture in vitro.

In order to develop scaffolds with improved biocompatibility for cell culture, hybrid scaffolds were fabricated by modifying poly(epsilon-caprolactone) (PCL) with silk fibroin (SF) in a porous structure. Scanning electronic microscopy revealed that the morphology of the PCL-SF hybrid scaffold was affected by the concentration of the SF solution. Availability of SF on the surface and the conformational transition induced by methanol treatment were proved by attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR), and wettability of the hybrid scaffold was greatly improved. To evaluate scaffold biocompatibility, human fibroblasts were cultured on the hybrid scaffold with the unmodified PCL scaffold as control. An MTT assay indicated that although fewer cells were initially held on the hybrid scaffold after one day of culture, comparable cell numbers were achieved after four days and significantly more cells proliferated on the hybrid after seven days. The cell morphology also indicated that the PCL-SF hybrid scaffold was favorable for cell culture. This study suggests that surface modification with SF would be an effective way to improve the biocompatibility of PCL, facilitating its application in practical tissue engineering.

Cell Adhesion↗

PubMed1998

Modifying risk for extracorporeal circulation: trial of four antiinflammatory strategies.

BACKGROUND: Despite recent rediscovery of beating heart cardiac surgical techniques, extracorporeal circulation remains appropriate for most heart operations. To minimize deleterious effects of cardiopulmonary bypass, antiinflammatory strategies have evolved. METHODS: Four state-of-the-art strategies were studied in a prospective, randomized, preoperatively risk stratified, 400-patient study comprising primary (n = 358), reoperative (n = 42), coronary (n = 307), valve (n = 27), ascending aortic (n = 9), and combined operations (n = 23). Groups were as follows: standard, roller pump, membrane oxygenator, methylprednisolone (n = 112); aprotinin, standard plus aprotinin (n = 109); leukocyte depletion, standard plus a leukocyte filtration strategy (n = 112); and heparin-bonded circuitry, centrifugal pumping with surface modification (n = 67). RESULTS: Analysis of variance, linear and logistic regression, and Pearson correlation were applied. Actual mortality (2.3%) was less than half the risk stratification predicted mortality (5.7%). The treatment strategies effectively attenuated markers of the inflammatory response to extracorporeal circulation. Compared with the other groups the heparin-bonded circuit had highly significantly decreased complement activation (p = 0.00001), leukocyte filtration blunted postpump leukocytosis (p = 0.043), and the aprotinin group had less fibrinolysis (p = 0.011). Primary end points, length of stay, and hospital charges, were positively correlated with operation type, age, pump time, body surface area, stroke, pulmonary sequelae, predicted risk for stroke, predicted risk for mortality, and risk strata/treatment group interaction (p = 0.0001). In low-risk patients, leukocyte filtration reduced length of stay by 1 day (p = 0.02) and mean charges by $2,000 to $6,000 (p = 0.05). For high-risk patients, aprotinin reduced mean length of stay up to 10 fewer days (p = 0.02) and mean charges by $6,000 to $48,000 (p = 0.0007). CONCLUSIONS: These pharmacologic and mechanical strategies significantly attenuated the inflammatory response to extracorporeal circulation. This translated variably into improved patient outcomes. The increased cost of treatment was offset for selected strategies through the added value of significantly reduced risk.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2004

Surface structural characterization of protein- and polymer-modified polystyrene microspheres by infrared-visible sum frequency generation vibrational spectroscopy and scanning force microscopy.

Structural investigations of bare and surface-modified polystyrene microspheres (beads) have been carried out by infrared-visible sum frequency generation (SFG) vibrational spectroscopy and scanning force microscopy (SFM). Bead surfaces have been modified by either the covalent linking of immunoglobulin G (IgG) and bovine serum albumin (BSA) or the nonspecific adsorption of a Pluronic surfactant. After surface modification with protein, SFG signals in the aliphatic CH-stretch region are detected at both the buffer/bead and air/bead interfaces, indicating that some amino acid residues in proteins adopt preferred orientations. SFG results indicate that the hydrophobic poly(propylene glycol) moieties in the Pluronic order when adsorbed onto the bead, at both the buffer/bead and air/bead interfaces, whereas hydrophilic poly(ethylene glycol) groups align to a lesser extent. SFG spectra also show that the phenyl rings of bare polystyrene beads in contact with air or buffer are ordered, with a dipole component directed along the surface normal, but become less ordered after the adsorption of either proteins or the polymer. Molecular orientation and ordering at the bead surface affect its hydrophobicity and aggregation behavior. SFM results reveal the formation of nonuniform islands when bare beads with more hydrophobic character are spun-cast onto a silica substrate. In the presence of adsorbed protein, a hexagonal packing of beads, with some defects, is observed, depending on the bulk pH and the type of attached protein. Adsorbed Pluronic causes the beads to aggregate in a disordered fashion, as compared to the behavior of bare and protein-modified beads.

Air↗

PubMed2000

Toward new biomaterials.

Polymers are widely used for a large range of medical devices used as biomaterials on a temporary, intermittent, and long-term basis. It is now well accepted that the initial rapid adsorption of proteins to polymeric surfaces affects the performance of these biomaterials. However, protein adsorption to a polymer surface can be modulated by an appropriate design of the interface. Extensive study has shown that these interactions can be minimized by coating with a highly hydrated layer (hydrogel), by grafting on the surface different biomolecules, or by creating domains with chemical functions (charges, hydrophilic groups). Our laboratory has investigated the latter approach over the past 2 decades, in particular the synthesis and the biological activities of polymers to improve the biocompatibility of blood-contacting devices. These soluble and insoluble polymers were obtained by chemical substitution of macromolecular chains with suitable groups able to develop specific interactions with biological components. Applied to compatibility with the blood and the immune systems, this concept has been extended to interactions of polymeric biomaterials with eukaryotic and prokaryotic cells. The design of new biomaterials with low bacterial attachment is thus under intensive study. After a brief overview of current trends in the surface modifications of biocompatible materials, we will describe how biospecific polymers can be obtained and review our recent results on the inhibition of bacterial adhesion using one type of functionalized polymer obtained by random substitution. This strategy, applied to existing or new materials, seems promising for the limitation of biomaterial-associated infections.

Adsorption↗

PubMed1997

Influence of polyethylene glycol graftings on the in vitro degradation and calcification of bovine pericardium.

Calcification is a frequent cause of the clinical failure of bio-prosthetic heart valves fabricated from glutaraldehyde pretreated bovine pericardium (GATBP). This article reports on various chemical techniques for grafting polyethylene glycol (PEG) on bovine pericardium, their biostability, and calcification. The process of calcification profile was studied by in vitro experiments via the incubation of pericardial samples in a metastable solution of calcium phosphate. The calcification profile of PEG-modified bovine pericardium through glutaraldehyde linkages was significantly reduced compared to other methods of grafting. The mechanical property of these PEG-modified tissues after enzyme (collagenase) digestion and calcification were also investigated. PEG grafting of BP via glutaraldehyde or hexamethylene diisocyanate had shown better mechanical stability compared to other grafting methods used. In conclusion, it seems that the surface modification of bovine pericardium through high molecular weight PEGs via glutaraldehyde linkages may provide new ways of controlling tissue biodegradation and calcification.

Animals↗

PubMed1994

Body distribution of 75Se-radiolabeled silica nanoparticles covalently coated with omega-functionalized surfactants after intravenous injection in rats.

Silica nanoparticles, radiolabeled with 75Selenium were coated with 14 types of omega-functionalized surfactants covalently bound to the particle surface. The particles were suspended in phosphate buffered saline (PBS) and injected intravenously via the tail vein of Wistar rats. The animals were sacrificed after 5 different time points (30 min, 2 h, 6 h, 24 h, and 7 d), and two samples of each organ and two blood samples were weighed into vials. The radioactivity of each sample was measured in a LKB-Wallac CliniGamma counter. Coated silica nanoparticles accumulated in the liver at much lower levels than other colloidal drug carriers after short time periods (30 min). The liver accumulation increased after longer time periods due to a natural redistribution process. Surface modification by increasing the hydrophilicity and thickness of coating yielded higher and longer persisting concentrations in the intestine, blood, and the muscles. Initially increased lung concentrations were decreasing with time, probably due to migration of the alveolar phagocytes.

Animals↗

PubMed2005

In vitro biological performances of phosphorylcholine-grafted ePTFE prostheses through RFGD plasma techniques.

Arterial prostheses made of microporous Teflon (ePTFE) are currently used in vascular surgery as bypasses for small and medium vessels. However, several clinical complications, such as thrombosis, frequently occur in these prostheses when implanted in humans. In this work, an original strategy was developed to improve the hemocompatibility of ePTFE prostheses, based on glow-discharge surface modification followed by chemical grafting of phosphorylcholine, known for its hemocompatible properties. This procedure leads to a covalent attachment of the molecules, therefore preventing their removal by shear stress induced by blood flow at the implant wall. The improvement of the blood compatibility properties of the modified ePTFE arterial prostheses have been investigated by in vitro tests such as thromboelastography, neutrophil adsorption, platelet aggregation, and cell cultures. These in vitro tests put in evidence that thrombogenicity index, platelet aggregation, and neutrophil adhesion were decreased by the molecule grafted on the prostheses. Moreover, the cell growth on the surface of the PRC-grafted prostheses was greatly enhanced in comparison to the virgin prosthesis. Based on these results, it could be concluded that PRC grafting on ePTFE prostheses permit to improve in vitro hemocompatibility and biocompatibility in comparison with their virgin counterpart.

Ammonia↗

PubMed2001

Biodegradable polymeric scaffolds for musculoskeletal tissue engineering.

Biodegradable scaffolds have played an important role in a number of tissue engineering attempts over the past decade. The goal of this review article is to provide a brief overview of some of the important issues related to scaffolds fabricated from synthetic biodegradable polymers. Various types of such materials are available; some are commercialized and others are still in the laboratories. The properties of the most common of these polymers are discussed here. A variety of fabrication techniques were developed to fashion polymeric materials into porous scaffolds, and a selection of these is presented. The very important issue of scaffold architecture, including the topic of porosity and permeability, is discussed. Other areas such as cell growth on scaffolds, surface modification, scaffold mechanics, and the release of growths factors are also reviewed. A summary outlining the common themes in scaffold-related science that are found in the literature is presented.

Animals↗

PubMed2006

Bias-assisted in vitro calcification of calcium disilicide growth layers on spark-processed silicon.

A dry-etch spark ablation method was used to produce calcium disilicide (CaSi2/Si) layers on silicon (Si) surfaces for the electrochemical growth of apatitic phosphates (calcium phosphate, CaP). CaSi2/Si composite electrodes readily calcify in vitro under the application of a small electric potential, and with proper treatment, the electrodeposition of CaP is localized to the sparked areas. In addition to increasing the local concentration of calcium, interfacial layers of CaSi2 on Si exhibit exceptional site selectivity towards CaP formation under bias due to the difference in conductivity between Si and CaSi2. The proposed mechanism for bias-assisted biomineralization of CaSi2/Si layers on spark-processed Si accounts for the physicochemical properties of deposited CaP films. This work also describes routes to surface modification of calcified composite electrodes with medicinally relevant compounds such as alendronate and norfloxacin. To assess the suitability of this material as a drug-delivery platform, release of the latter compound was also monitored as a function of time.

Anti-Infective Agents↗

PubMed2006

Role of heteroatoms in activated carbon for removal of hexavalent chromium from wastewaters.

Heteroatoms are elements including sulfur, nitrogen, oxygen and hydrogen which are found on the surface of activated carbons. This study investigated the surface modification arising from heteroatoms bonding to carbon aromatic rings within the activated carbon and their corresponding influence on the chromium adsorption process. Activated carbons were prepared from bagasse by physical. Chromium removal capacities of these activated carbons by adsorption and reduction were determined. Models which related the chromium adsorption and reduction capacities of activated carbons to carbon acidity and heteroatom site concentrations were established using multi-variable linear regression method. It was found the individual heteroatoms contributed separately to the basicity of the carbon which in turn determined the mechanism by which chromium was removed from solution. The surface areas of the carbons were also observed to influence the adsorption and reduction of chromium. These understandings provide the fundamental method of optimising chromium removal through suitable control of carbon surface chemistry and textural properties.

Carbon↗

PubMed2001

Subclinical, non-erythematous irritation with an open assay model (washing): sodium lauryl sulfate (SLS) versus sodium laureth sulfate (SLES).

Compared to exaggerated hand washing procedures, an open non-exaggerated assay better approximates consumer surfactant use. Our goal was to observe skin surface modifications induced by an open test with regard to discriminating between surfactant solutions. This human in vivo assay provided information about the effect of only three washes at the laboratory and a week of at-home use. Dorsal hand and volar forearm were compared. The results demonstrated that this clinical model permits exploration of subclinical surfactant-induced irritation. Both the volar forearm and the dorsal hand are capable of discriminating between the effects of sodium lauryl sulfate (SLS) and sodium laureth sulfate (SLES). Squamometry proved to be a sensitive assessment technique for detecting surfactant-induced subclinical skin surface alterations and for differentiating surfactant effects in this open application assay, in as few as three washes.

Adult↗