Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “surface modification”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 145 records · Page 8Linked to original sources
PubMed2001

Effect of heparin surface modification in reducing silicone oil adherence to various intraocular lenses.

PURPOSE: To evaluate surface properties of various intraocular lenses (IOLs), including a newly fabricated heparin-surface-modified (HSM) silicone IOL, with special reference to their efficiency in reducing potential silicone oil adherence to the IOL optics. SETTING: Center for Research on Ocular Therapeutics and Biodevices, Department of Ophthalmology, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA. METHODS: Five groups of rigid and foldable IOLs were analyzed in an in vitro test for the percentage of silicone oil adherence: a single-piece foldable hydrophilic-acrylic IOL (n = 9); a single-piece rigid poly(methyl methacrylate) (PMMA) IOL with HSM coating of the lens optic (n = 9); a 3-piece foldable silicone optic IOL with HSM coating of the optic (n = 10); a single-piece standard rigid PMMA IOL (n = 7); and a standard 3-piece foldable silicone optic IOL (n = 9). After the IOLs were immersed in water and then in silicone oil, gross photographs taken. Image analysis was performed to evaluate the percentage of silicone oil coverage of the anterior and posterior surfaces of each IOL optic. RESULTS: The mean silicone oil coverage of the hydrophilic-acrylic IOLs was 5.6% +/- 2.5% (SD); of the HSM PMMA IOLs, 6.2% +/- 4.3%; of the HSM silicone optic IOLs, 6.7% +/- 3.2%; and of the standard PMMA IOLs, 20.3% +/- 13.3%. The mean silicone oil coverage was greatest on the standard silicone optic IOLs, 98.2% +/- 3.1%. CONCLUSIONS: Intraocular lenses with a hydrophilic optic have less tendency toward adherence to silicone oil than more hydrophobic designs. A foldable silicone IOL with heparin surface modification can significantly reduce potential silicone oil adherence, comparable to the level achievable with the rigid HSM PMMA designs. Two new foldable IOL styles, the HSM silicone IOL and IOLs in the general class of hydrophilic-acrylic, were highly efficacious in reducing silicone oil adherence. There is now a real choice of foldable lenses for patients with actual or potential vitreoretinal diseases.

Acrylic Resins↗
PubMed2005

Ultralow energy ion beam surface modification of low density polyethylene.

Ultralow energy Ar+ and O+ ion beam irradiation of low density polyethylene has been carried out under controlled dose and monoenergetic conditions. XPS of Ar+-treated surfaces exposed to ambient atmosphere show that the bombardment of 50 eV Ar+ ions at a total dose of 10(16) cm(-2) gives rise to very reactive surfaces with oxygen incorporation at about 50% of the species present in the upper surface layer. Using pure O+ beam irradiation, comparatively low O incorporation is achieved without exposure to atmosphere (approximately 13% O in the upper surface). However, if the surface is activated by Ar+ pretreatment, then large oxygen contents can be achieved under subsequent O+ irradiation (up to 48% O). The results show that for very low energy (20 eV) oxygen ions there is a dose threshold of about 5 x 10(15) cm(-2) before surface oxygen incorporation is observed. It appears that, for both Ar+ and O+ ions in this regime, the degree of surface modification is only very weakly dependent on the ion energy. The results suggest that in the nonequilibrium plasma treatment of polymers, where the ion flux is typically 10(18) m(-2) s(-1), low energy ions (<50 eV) may be responsible for surface chemical modification.

Argon↗
PubMed1984

The effect of aging and surface modification on the mechanical properties of dense aluminum oxide.

The effect of in vivo aging and surface texturing on the mechanical properties of dense aluminum oxide were studied. The modulus of rupture and Weibull modulus were determined in air and Ringer's solution using a 3-point bend test. The results showed that the in vivo environment sealed off microcracks either chemically or by tissue ingrowth which strengthened the alumina. The surface modification, however, tended to create more microcracks and stress concentrations at the surface indentations which tended to weaken the alumina.

Aluminum↗
PubMed2006

Photolithographically patterned surface modification of poly(dimethylsiloxane) via UV-initiated graft polymerization of acrylates.

Patterned surface modification of poly(dimethylsiloxane) (PDMS) is achieved by combining ultraviolet-initiated graft polymerization (UV-GP) and photolithography. Poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) patterns were grafted onto PDMS with micrometer-scale feature edge resolution. The morphology and chemical composition of the grafted layers were assessed by optical and atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and XPS imaging. AFM section analyses demonstrated the deposition of 33 +/- 1 and 62 +/- 8 nm thick patterned films of PAA and PMAA, respectively. Spatially resolved C 1s XPS provided images of carboxylic acid functionalities, verifying the patterned deposition of acrylate films on PDMS. These observations demonstrate the general usefulness of UV-GP and photolithography for micropatterning.

Journal Article↗
PubMed2002

Cardiopulmonary bypass copolymer surface modification reduces neither blood loss nor transfusions in coronary artery surgery.

OBJECTIVE: Surface-modifying additives (SMA) have been suggested for improving cardiopulmonary bypass (CPB) circuit biocompatibility, potentially minimizing inflammatory complications and bleeding associated with CPB. The purpose of this prospective, randomized clinical study was to compare a novel copolymer surface-modified CPB circuit (SMARXT; COBE Cardiovascular) against the unmodified circuit. METHODS: We randomized 122 patients with isolated coronary artery disease subjected to first-time surgery on CPB into either the SMA (n = 62) or the control group (n = 60). Exclusion criteria included renal insufficiency, liver disease, coagulopathy, anticoagulation therapy < 6 days preop, carotid artery stenosis > 70 %, and a history of stroke. We collected perioperative clinical data including drainage blood loss, transfusion requirements, duration of mechanical ventilation, and ICU stay. Platelet function was determined pre- and post-CPB. RESULTS: SMA patients received 3.2 +/- 0.9 (SD) grafts during 48 +/- 16 min of aortic cross clamp and 91 +/- 30 min CPB (Control: 3.0 +/- 0.9 grafts; p = 0.33, 46 +/- 14 min AXC; p = 0.36, and 84 +/- 23 min CPB; p = 0.14). In the SMA group, 23 patients (37 %) received red blood-cell transfusions, 9 patients (15 %) fresh frozen plasma, and 3 patients (5 %) received platelets (control: n = 27 [46 %], p = 0.44; n = 10 [17 %], p = 0.91; and n=4 [7 %], p = 0.71, respectively). Platelet count on CPB fell to the same level in both groups. In SMA patients, platelet function decreased from 94.2 +/- 24.9 % pre-CPB to 79.5 +/- 32.8 % post-CPB (p = 0.043) (control: from 87.7 +/- 25.6 % to 69.4 +/- 34.7 %; p = 0.001). Postoperative drainage blood loss, mechanical ventilation duration, and ICU stay were similar in both groups (p > 0.3). One patient of the control group was excluded due to surgical bleeding, and one SMA patient died. CONCLUSIONS: Our results show that the surface-modified CPB circuit decreased neither blood loss nor transfusions despite slightly better platelet function preservation compared to the unmodified circuit. This type of CPB circuit surface modification does not appear to improve clinical outcome in low-risk coronary artery surgery patients.

Aged↗
PubMed2005

Surface modification of magnetic nanoparticles capped by oleic acids: characterization and colloidal stability in polar solvents.

The lyophobic surface of monodisperse magnetic nanoparticles capped by oleic acid was made to be more lyophilic by ozonolysis to increase the stability of the suspension in polar solvents like ethanol. The ozone oxidatively cleaved the double bond of oleic acid to form carbonyl and carboxyl groups on the surface of the nanoparticles. Additionally, interfacial ligand exchange of the capping molecules was applied to make the hydrophobic particle surface more hydrophilic. The magnetic particles showed enhanced miscibility and short-term stability in water after interfacial ligand exchange. The structure changes of the capping molecules on the nanoparticle surfaces were investigated using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). From these spectroscopy studies, the cleavage of the oleic acid and the formations of the carboxyl and carbonyl groups on the particle surface were confirmed. The shape and the magnetic properties of the nanoparticles were maintained after the surface modification. Ozonolysis is an effective method in modifying the lyophobic surface of the magnetic nanoparticles.

Journal Article↗
PubMed1997

A photochemical method for the surface modification of poly(etherurethanes) with phosphorylcholine-containing compounds to improve hemocompatibility.

Phosphorylcholine groups attached to polymer surfaces are known to improve hemocompatibility. A photochemical method is presented to couple phosphorylcholine-containing aryl azides to poly(etherurethane) surfaces (PEUs). Two aryl azides that consist of a photoactivatable 4-azidobenzoyl group, a short spacer chain, and a phosphorylcholine endgroup were synthesized. The two compounds differ only in the type of spacer used: triethylene glycol for compound 1 and hexanediol for compound 2. These compounds were physically adsorbed to PEU surfaces. Upon UV irradiation, reactive intermediates are formed that react with nucleophilic groups on the polymer surface. The modified surfaces showed decreased underwater contact angles, indicating that hydrophilic phosphorylcholine groups are present at the surface. ESCA measurements showed the presence of phosphorus and positively charged nitrogen atoms in the outermost polymer layers (analyzed depth about 50 A), which is a strong indication of the presence of phosphorylcholine groups. Hemocompatibility in vitro was tested with thrombin generation assays and platelet adhesion tests. In thrombin generation assays the clotting time of platelet-rich plasma in contact with the polymer surface is determined. Clotting times were clearly prolonged for the modified surfaces. Surfaces modified with compound 2 showed slightly higher clotting times than those modified with compound 1. Repeated surface modification with compound 2 further increased the clotting time. For the tested surfaces an increase in the clotting time corresponds to an increase in the concentration of phosphorylcholine groups at the surface (as measured by ESCA and contact angle). Platelet adhesion studies with scanning electron microscopy demonstrated that fewer platelets (showing less activation) adhered to the modified surfaces than to the unmodified polyurethane.

Blood↗
PubMed2005

Photo-immobilization of a phospholipid polymer for surface modification.

A photo-reactive polymer having a phospholipid polar group was prepared, and the polymer was photo-immobilized on polymeric surfaces, where its interactions with biocomponents were investigated. By using a photo-immobilization method, the polymer was used for surface modification of polyethylene and polypropylene, polymers whose surfaces were not treated in our previous development of the phosphorylcholine-derived polymer. The photo-reactive polymer was synthesized by a coupling reaction involving copolymer consisting of 2-methacryloyloxyethyl phosphorylcholine and methacrylic acid with 4-azidoaniline. When the polymer was unpattern immobilized on the surface, X-ray photo-electron spectroscopic analysis and static contact angle measurements were performed. It was shown that the surface was covered with phospholipid polar groups. Micropattern immobilization was carried out using a micropatterned photo-mask. Measurements using atomic force microscopy showed that the swelled micropatterned polymer was five times as thick as the dried one. Protein adsorption and platelet adhesion were reduced on the polymer-immobilized regions. Mammalian cells did not adhere, and formed aggregates on the immobilized regions. In conclusion, the photo-reactive phospholipid polymer was covalently immobilized on the conventional polymer surfaces and it tended to reduce interactions with proteins and cells.

Adsorption↗
PubMed2005

Formulation and surface modification of poly(ester-anhydride) micro- and nanospheres.

This report presents the formulation and surface modification of poly(ester-anhydride) copolymers. Two synthetic schemes were used to generate a variety of copolymers with varying compositions and molecular weights. These polymers were formulated into both micro- and nanospheres using a water-in-oil-in-water double emulsion technique. Microspheres were between 3 and 10 microm in diameter; whereas, nanospheres were between 300 and 500 nm. Finally, both micro- and nanospheres were surface modified using cystamine and quantified, following cystamine reduction, with DTNB (Ellman's reagent). Surface labeling was observed at 0.20-35 micromol/g for microspheres and 0.6-100 micromol/g for nanospheres and followed the expected trend of increased labeling with increased polyanhydride content.

Absorbable Implants↗
PubMed2004

Surface modification of the channels of poly(dimethylsiloxane) microfluidic chips with polyacrylamide for fast electrophoretic separations of proteins.

The electrophoresis of proteins was investigated using poly(dimethylsiloxane) (PDMS) microfluidic chips whose surfaces were modified with polyacrylamide through atom-transfer radical polymerization. PDMS microchips were made using a glass replica to mold channels 10 microm high and 30 microm wide, with a T-intersection. The surface modification of the channels involved surface oxidation, followed by the formation of a self-assembled monolayer of benzyl chloride initiators, and then atom-transfer radical polymerization to grow a thin layer of covalently bonded polyacrylamide. The channels filled spontaneously with aqueous buffer due to the hydrophilicity of the coating. The resistance to protein adsorption was studied by open-channel electrophoresis for bovine serum albumin labeled with fluorophor. A plate height of 30 microm, corresponding to an efficiency of 33 000 plates/m, was obtained for field strengths from 18 to 889 V/cm. The lack of dependence of plate height on field strength indicates that there is no detectable contribution to broadening from adsorption. A 2- to 3-fold larger plate height was obtained for electrophoresis in a 50-cm polyacrylamide-coated silica capillary, and the shape of the electropherogram indicated the efficiency is limited by a distribution of species. The commercial capillary exhibited both reversible and irreversible adsorption of protein, whereas the PDMS microchip exhibited neither. A separation of lysozyme and cytochrome c in 35 s was demonstrated for the PDMS microchip.

Acrylic Resins↗
PubMed2006

Surface modification methods for enhanced device efficacy and function.

Currently available microfluidic devices can accomplish a variety of tasks useful in molecular biology. When moving analytical processes to a microenvironment, the properties of the device surface play a larger role in the functioning of the device. Surface modification may become necessary or advantageous for the purpose of control of the functional mechanics of the device, keeping cell components from adsorbing, attaching antibodies to the surface for detection of biological components, and attaching a functional bonding complex. Modification of the surface of microfluidic devices for the control of flow and device function, or for functionalization of the surface to tailor the device to a specific use, can be accomplished in numerous bench-top, postfabrication procedures. The use of polyelectrolyte multilayers, ultraviolet grafting of polymers, and polydimethylsiloxane/surfactant coating to control flow and mitigate adsorption is discussed. In addition, the functionalization of devices through amine termination of surfaces, and immobilization of biotin within a phosphotidylcholine bilayer is detailed.

Biotin↗
PubMed2003

Surface modification of poly(vinylidenefluoride) to improve the osteoblast adhesion.

Cell adhesion to biomaterials is mediated primarily by the interaction between surface bound proteins and corresponding receptors on the membrane of the cells. The attachment of fibronectin onto poly(vinylidenefluoride) (PVDF) surface and the application of PVDF as biomaterial in bone contact was the subject of our study. PVDF is a biomaterial established for soft tissue applications. Surface modifications of PVDF were performed by plasma induced graft copolymerisation of acrylic acid or CVD polymerisation of 4-amino[2.2]paracyclophane. The provided functionalised PVDF surface was used to immobilise fibronectin using different techniques. All modification steps were verified by means of X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared spectroscopy (IR-ATR) and contact angle measurements. Surface topology was studied by atomic force measurements (AFM). Protein adsorption was controlled by enzyme linked immunosorbent assay (ELISA). Cell attachment was enhanced if physically adsorbed fibronectin was used, while enhanced attachment and proliferation were induced by covalently binding fibronectin to the surface modified PVDF.

Acetates↗
PubMed1996

Surface modification of chitosan membranes by complexation-interpenetration of anionic polysaccharides for improved blood compatibility in hemodialysis.

Chitosan membrane surface was modified by complexation and interpenetration of anionic polysaccharides--heparin and dextran sulfate--for improved blood compatibility in hemodialysis. Electron spectroscopy for chemical analysis results showed a characteristic sulfur (S) and sodium (Na) peaks after modification with dextran sulfate. The sulfur/carbon (S/C) atomic composition ratio increased from 0.03 to 0.08 when the bulk dextran sulfate concentration used for modification was increased from 2.5 to 10 mg ml-1. The permeability of urea and creatinine did not change significantly upon modification with heparin or dextran sulfate. Surface modification, however, did decrease the permeability coefficients of glucose, vitamin B-2, and vitamin B-12. Unlike Cuprophan, chitosan and surface-modified chitosan membranes did not significantly activate the complement system as measured by the serum iC3b concentration. Compared to forty and sixty fully-activated platelets present on control surfaces, surface modification with heparin and dextran sulfate significantly reduced the number of adherent platelets per 25,000 microns 2 area and the extent of platelet activation. Surface modification with anionic polysaccharides, however, did significantly shorten the plasma recalcification time leading to fibrin clot formation. The results of this study show that chitosan membrane surface can be modified by complexation-interpenetration of anionic modifying agents. The modified membranes do resist complement activation and platelet adhesion and activation.

Adult↗
PubMed2002

Surface modification and characterization of microfabricated poly(carbonate) devices: manipulation of electroosmotic flow.

Poly(carbonate), PC, surfaces are chemically modified by treatment with sulfur trioxide gas. Sulfur trioxide gas sulfonates the aromatic rings of the poly(carbonate) surfaces, making the surfaces more hydrophilic. Sulfonation of the poly(carbonate) surface is confirmed by infrared spectroscopy. The modified polymer surfaces are found to be smoother in comparison to their unmodified counterparts, as noted by scanning force microscopy. The effects of the surface modification on electroosmotic flow are studied at a pH range of 4-10. The electroosmotic flow in sulfonated poly(carbonate) microchannels was found to be significantly higher than that in unmodified poly(carbonate) microchannels at pH values below 8.

Electrophoresis↗
PubMed2002

Surface modification of Sylgard-184 poly(dimethyl siloxane) networks by ultraviolet and ultraviolet/ozone treatment.

We report on the surface modification of Sylgard-184 poly(dimethyl siloxane) (PDMS) networks by ultraviolet (UV) radiation and ultraviolet/ozone (UVO) treatment. The effects of the UV light wavelength and ambient conditions on the surface properties of Sylgard-184 are probed using a battery of experimental probes, including static contact angle measurements, Fourier transform infrared spectroscopy, near-edge X-ray absorption fine structure, and X-ray reflectivity. Our results reveal that when exposed to UV, the PDMS macromolecules in the surface region of Sylgard-184 undergo chain scission, involving both the main chain backbone and the side groups. The radicals formed during this process recombine and form a network whose wetting properties are similar to those of a UV-modified model PDMS. In contrast to the UV radiation, the UVO treatment causes very significant changes in the surface and near-surface structure of Sylgard-184. Specifically, the molecular oxygen and ozone created during the UVO process interact with the UV-modified specimen. As a result of these interactions, the surface of the sample contains a large number of hydrophilic (mainly -OH) groups. In addition, the material density within the first approximately 5 nm reaches about 50% of that of pure silica. A major conclusion that can be drawn from the results and analysis described in this work is that the presence of the silica fillers in Sylgard-184 does not alter the surface properties of the UVO- and UV-modified Sylgard-184.

Journal Article↗
PubMedDate not supplied

Evaluation of chemically-induced pore surface modifications on rock cores.

Chemical modification of pore surface properties due to active components of crude oils could significantly affect production processes. Specific chemical treatments can prevent surface alteration, protecting pores from deposition of heavy oils components. Both relaxation times analysis and nuclear magnetic resonance (NMR) imaging technique are a valuable method for nondestructive monitoring of solid/liquid interface alteration especially if applied to heterogeneous rock cores, which are impossible to study using conventional methods (e.g., Amott tests and dynamic angle contact). In our work, we examined carbonate core plugs subjected to aging treatments in crude oil. Relaxation times measurement, revealing modifications of fluid/surface interactions and imaging, was applied in characterise heterogeneous systems and reveal fluid distribution changes. Nuclear magnetic resonance results were compared with a special microscopy technique (Cryo-SEM) that allows observation of fluids at the pore level, providing a better understanding of the processes involved.

Geologic Sediments↗
PubMed2006

Activated carbon with excellent chromium(VI) adsorption performance prepared by acid-base surface modification.

In the present work, activated carbon (AC) with excellent Cr(VI) adsorption performance especially at low concentrations was prepared by an acid-base surface modification method. Raw activated carbon (AC(0)) was first oxidized in boiling HNO(3) (AC(1)), then treated with a mixture of NaOH and NaCl (AC(2)). Batch equilibrium and continuous column adsorption were conducted to evaluate the adsorption performance. Boehm titration, elemental analysis, and N(2)/77K adsorption isotherm methods were used to characterize the surface properties and pore structure of modified ACs. The results revealed that the modified AC exhibited excellent Cr(VI) adsorption performance in terms of adsorption capacity and adsorption rate: AC(2)>AC(1)>AC(0). Modification caused S(BET) to decrease and the total number of surface oxygen acidic groups to increase. HNO(3) oxidization produced positive acid groups, and subsequently NaOH treatment replaced H(+) of surface acid groups by Na(+), and the acidity of AC decreased. The main cause of higher Cr(VI) adsorption capacity and rate for AC(2) was the presence of more oxygen surface acidic groups and suitable surface acidity. HNO(3)-NaOH modification shows potential for the preparation of high quality AC for the effective removal of low concentrations of Cr(VI).

Adsorption↗
PubMed2005

Surface modification of polyacrylonitrile-based membranes by chemical reactions to generate phospholipid moieties.

A novel approach for the surface modification of poly(acrylonitrile-co-2-hydroxyethyl methacrylate) (PANCHEMA) membranes by introducing phospholipid moieties is presented, which involved the reaction of the hydroxyl groups on the membrane surface with 2-chloro-2-oxo-1,3,2-dioxaphospholane (COP) followed by the ring-opening reaction of COP with trimethylamine. The chemical changes of phospholipid-modified acrylonitrile-based copolymers (PMANCP) membranes were characterized by Fourier transfer infrared spectroscopy and X-ray photoelectron spectroscopy. The surface properties of PMANCP membranes were evaluated by pure water contact angle, protein adsorption, and platelet adhesion measurements. Pure water contact angles measured by the sessile drop method on PMANCP membranes were obviously lower than those measured on the PANCHEMA membranes and decreased with the increase of the content of phospholipid moieties on the membrane surface. It was found that the bovine serum albumin adsorption and platelet adhesion were suppressed significantly with the introduction of phospholipid moieties on the membranes surface. These results demonstrated that the described process was an efficient way to improve the surface biocompatibility for the acrylonitrile-based copolymer membrane.

Acrylic Resins↗