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Results for “surface modification”

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PubMed1999

Investigations into the reduction of powder adhesion to stainless steel surfaces by surface modification to aid capsule filling.

The adhesion force of powder particles to stainless steel surfaces, which had been modified by various metal coatings, has been measured using a centrifuge technique. The surfaces were characterised by surface roughness and surface free energy measurements, whereas the particles, which had a particle size of 32-45 microns, were characterised by their surface free energy only. The roughness of the surfaces was found to be similar, so that changes in the adhesion properties of the powders to these surfaces could not be due to a change in this surface property. However, there was a major difference in the surface free energy parameters of the surfaces. The surface free energy varied from a nearly non-polar character to strong Lewis-base. The adhesion force of pregelatinised starch and lactose monohydrate particles increased with the increasing base character of the surfaces. In principle this behaviour could also be seen for calcium carbonate particles. However, here the order of the adhesion forces to the surfaces tested was disrupted on one occasion because of a pronounced influence of particle and surface hardness on this property. In general, the ranking of the adhesion forces matched observations made during capsule filling on a Bosch GKF-400 tamp-filling machine. It was therefore concluded that a metal coating of the tamping pins would be able to reduce powder adhesion. In order to identify the best coating, centrifugal adhesion force measurements could be undertaken, or surface free energy measurements could be made. The results found suggest that a surface finish by means of chromium nitride coating provided, in most cases, a significant reduction of the powder adhesion. For very hard powder particles such as inorganic excipients the hardness of the surfaces must also be increased. In these cases plasma-coating of chromium appears helpful.

Capsules↗

PubMed2002

Calcified nanostructured silicon wafer surfaces for biosensing: effects of surface modification on bioactivity.

The growth of known biologically-relevant mineral phases on semiconducting surfaces is one strategy to explicitly induce bioactivity in such materials, either for sensing or drug delivery applications. In this work, we describe the use of a spark ablation process to fabricate deliberate patterns of Ca(10)(PO4)6(OH)2 on crystalline Si (calcified nanoporous silicon). These patterns have been principally characterized by scanning electron microscopy in conjunction with elemental characterization by energy dispersive x-ray analysis. This is followed by a detailed comparison of the effects of fibroblast adhesion and proliferation onto calcified nanoporous Si, calcified nanoporous Si derivatized with alendronate, as well as control samples of an identical surface area containing porous SiO2. Fibroblast adhesion and proliferation assays demonstrate that a higher density of cells grow on the Ca3(PO4)2/porous Si/SiO2 structures relative to the alendronate-modified surfaces and porous Si/SiO2 samples.

Biosensing Techniques↗

PubMed1989

[Polysorbates for hemoperfusion. The effect of polysorbate surface modification on morphology, coagulation, fibrinolysis, and kallikrein formation].

In the work the influence of surface sulfonated polymer sorbents with styrene-divinylbenzene (Vinylsorb SS) modified by amino acids upon the morphological picture of blood and proteins of the coagulation system was tested. Those sorbents do not exert a remarkable influence upon erythrocytes and coagulation proteins but they adsorb blood platelets, leucocytes and they activate prekallikrein system. Vinylsorb SS has the best influence because it adsorbs few platelets and activates prekallikrein system to the least extent.

Adsorption↗

PubMed1996

Spectroscopic study of nickel(II) hydroxide surface modifications induced by a small iron(III) addition.

Comparative Auger electron spectroscopic data on the surface composition and depth profiling for beta-Ni(OH)(2) and Ni(OH)(2) coprecipitated with iron(III) (3 at.%) are given showing a non-uniform distribution of the latter. They are considered together with their structural characteristics obtained using Fourier transform infrared spectroscopy (both samples) and Mössbauer spectroscopy (Fe-containing sample). The results obtained provide an explanation for the specific behaviour of the Fe(III)-doped nickel(II) hydroxide in heterogeneous processes (adsorption, electrocatalysis).

Journal Article↗

PubMed1992

Control of staphylococcal adhesion to polystyrene surfaces by polymer surface modification with surfactants.

The adherence of three clinical isolates of Staphylococcus epidermidis to model polystyrene surfaces was studied in vitro using epifluorescent image analysis. A series of 16 Pluronic surfactants (A-B-A block copolymers where A is poly(ethylene oxide) (PEO) and B is poly(propylene oxide) (PPO)) were used as surface modifiers for the model polystyrene surfaces. Substantial reductions (up to 97%) in bacterial adhesion levels were achieved with all copolymers tested, irrespective of the PPO or PEO block lengths. It appears likely that such treatments create a sterically stabilized surface with adsorbed PEO chains, conferring nonspecific anti-adhesive properties which can limit bacterial attachment.

Bacterial Adhesion↗

PubMed2005

The effect of the surface modification of titanium using a recombinant fragment of fibronectin and vitronectin on cell behavior.

The surface of titanium implants is in direct contact with host tissue and plays a critical role in determining biocompatibility. Fibronectin (FN) and vitronectin (VN) are major cell adhesive proteins found in the extracellular matrix (ECM) of various tissues, and in circulating blood. The aim of this study was to evaluate the engineered biomimetic surface of titanium by using recombinant fragment of FN(8-10) and VN(NTD) that contains the binding site for integrins. MC3T3-E1 cells seeded upon the FN(8-10)-coated titanium showed a marked increase in cell adhesion, proliferation, and differentiation over VN(NTD)-coated titanium. In addition, we confirmed that the surface properties of titanium prefer for FN(8-10) over VN(NTD) (p<0.05) in protein adhesion. These results suggest that the FN(8-10)-modified titanium surface can be used to improve the osseointegration of titanium implants by enhancing bone formation.

3T3 Cells↗

PubMed1988

Improved in vivo endothelialization of prosthetic grafts by surface modification with fibronectin.

Endothelial cell growth in vitro is enhanced by coating with fibronectin the surface on which cells grow. Similar coating of prosthetic arterial grafts may promote in vivo graft endothelialization if graft patency is not adversely affected. In each of 15 dogs, two fibronectin-coated polytetrafluoroethylene grafts and two grafts that were not coated were implanted. One graft in each pair was seeded with autologous endothelial cells, so that four different grafts were studied in each animal: a coated, seeded graft; a coated graft that was not seeded; a seeded graft that was not coated; a graft that was neither coated nor seeded. At 2, 4, and 8 weeks, grafts from five animals were examined for patency, surface endothelialization, and indium 111 platelet reactivity. After seeding, surface coverage by endothelium of coated grafts was more complete and more rapid than in uncoated grafts (64% +/- 23% vs 31% +/- 13% at 4 weeks, p less than 0.05). Without seeding, coated grafts also appeared to have increased endothelial cell ingrowth compared with plain grafts (48.8% +/- 15.1% vs 37.6% +/- 1.5% at 8 weeks). Early (2-week) platelet reactivity of coated grafts was increased (p = 0.06), but patency was not adversely affected. Thus fibronectin coating of prosthetic grafts promotes surface endothelialization in vivo without altering graft patency.

Animals↗

PubMed2006

Laser surface modification of Ti--6Al--4V: wear and corrosion characterization in simulated biofluid.

Laser surface melting (LSM) of Ti-6Al-4V is performed in argon to improve its properties, such as microstructure, corrosion, and wear for biomedical applications. Corrosion behavior is investigated by conducting electrochemical polarization experiments in simulated body fluid (Ringer's solution) at 37 C. Wear properties are evaluated in Ringer's solution using pin-on-disc apparatus at a slow speed. Untreated Ti-6Al-4V contains alpha+beta phase. After laser surface melting, it transforms to acicular alpha embedded in the prior beta matrix. Grain growth in the range of 65-89 microm with increase in laser power from 800 to 1500 W due to increase in associated temperature is observed. The hardness of as-laserprocessed Ti-6Al-4V alloy is more (275-297 HV) than that of the untreated alloy (254 HV). Passivation currents are significantly reduced to < 4.3 microA/cm2 after laser treatment compared to untreated Ti-6Al-4V (approximately 12 microA/cm2). The wear resistance of laser-treated Ti-6Al-4V in simulated body fluid is enhanced compared to that of the untreated one. It is the highest for the one that is processed at a laser power of 800 W. Typical micro-cutting features of abrasive wear is the prominent mechanism of wear in both untreated and as-laser-treated Ti-6Al-4V. Fragmentation of wear debris assisted by microcracking was responsible for mass loss during the wear of untreated Ti-6Al-4V in Ringer's solution.

Alloys↗

PubMed2001

Surface modification of stainless steel by grafting of poly(ethylene glycol) for reduction in protein adsorption.

The surface of stainless steel was first modified by the silane coupling agent (SCA), (3-mercaptopropyl)trimethoxysilane. The silanized stainless-steel surface (SCA-SS surface) was subsequently activated by argon plasma and then subjected to UV-induced graft polymerization of poly(ethylene glycol)methacrylate (PEGMA). The chemical structures and composition of the pristine, silane-treated, plasma-treated and PEGMA graft-polymerized stainless-steel coupon surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. The graft polymerization of PEGMA onto the plasma-pretreated SCA-SS surface was studied with different argon plasma pretreatment time, macromonomer concentration, and UV graft polymerization time. In general, a brief plasma pretreatment, high PEGMA concentration, and long UV graft polymerization time readily resulted in a high graft concentration. The PEGMA graft-polymerized stainless-steel coupon (PEGMA-g-SCA-SS) with a high graft concentration, and thus a high PEG content, was found to be very effective in preventing bovine serum albumin and gamma-globulin adsorption.

Adsorption↗

PubMed2006

Surface modification of polystyrene using polyaniline nanostructures for biomolecule adhesion in radioimmunoassays.

The selection of an appropriate surface as a solid phase for coupling antibodies is a critical step in the development of solid-phase immunoassays. Availability of a new method of preactivating the surface of polystyrene tubes with a layer of another polymer for enhanced immobilization of antibodies seems to be promising. In this paper, we report the activation of a polystyrene surface using a layer of polyaniline and its effect on immobilizing antibodies for use as a solid phase in a T3 immunoassay. The modified surface on the polystyrene was characterized by optical absorption, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The modified tubes were coated with antibody and evaluated for their performance in the assay and validated for radioimmunoassay of T3. AFM images of the modified surface showed an enhancement in the surface roughness (Ra of 20.2 nm), as compared to an unmodified surface (Ra of 6 nm), allowing more adsorption of antibodies to the surface. XPS revealed the presence of N (binding energy approximately 400 eV) on the modified surface, which could help the antibody molecules to bind to these preactivated (modified) tubes. The modified tubes, when coated with antibody, not only showed an increase in the binding with the radioiodinated tracer but also improved the precision of coating the antibody. The present method of activating polystyrene surfaces is simple, does not involve severe chemical treatment, and may have wide applicability to functionalize other supports for immobilizing biomolecules.

Adhesiveness↗

PubMed2004

Laser surface modification of silicone rubber to reduce platelet adhesion in vitro.

To improve the blood compatibility, the surface of polydimethylsiloxane (PDMS) films were irradiated using a CO2-pulsed laser. Acrylamide (AAm) was grafted onto a pre-irradiated surface. The AAm-grafted and laser-treated films were characterized using different techniques. Platelet adhesion and activation onto the AAm-grafted PDMS, laser-treated (ungrafted) and unmodified PDMS film surfaces were compared. Data from in vitro assays indicated that the platelet adhesion was reduced on the AAm-grafted PDMS and laser treated PDMS films in comparison with the unmodified PDMS. The laser-irradiated sample showed the minimum platelet adhesion. It seems that laser irradiation onto a silicone rubber surface is a versatile technique to produce anti-thrombogenic surface for biomaterial applications.

Acrylamide↗

PubMed2003

Toward spinal cord injury repair strategies: peptide surface modification of expanded poly(tetrafluoroethylene) fibers for guided neurite outgrowth in vitro.

Expanded poly(tetrafluoroethylene) fibers were surface modified using an ultraviolet-activated mercury/ammonia reaction to yield amine-functional groups for the coupling of laminin-derived cell adhesive peptides CYIGSR, CDPGYIGSR, CIKVAV, and CQAASIKVAV. Surface elemental composition, determined by X-ray photoelectron spectroscopy, and radiolabeling data indicated that the amount of peptide introduced was approximately equivalent regardless of peptide type, yet mixed peptide surfaces had approximately 60% YIGSR and 40% IKVAV. The peptide-modified surfaces were compared in terms of the response of dorsal root ganglia with neurite length and number of cells attached to each fiber measured. All peptide-functionalized surfaces had a greater cellular response than the aminated ePTFE and ePTFE controls. Surfaces modified with extended peptide sequences CDPGYIGSR and CQAASIKVAV demonstrated a greater cellular response than those modified with the shorter peptide sequences CYIGSR and CIKVAV, respectively, likely because the extended peptides more closely mimic the three-dimensional conformation that the peptides maintain in laminin. Differences in neurite extension were evident among the peptide-functionalized surfaces, with the longest neurites observed on surfaces modified with both CQAASIKVAV and CDPGYIGSR. The "guidance capacity" of the fibers as a function of fiber diameter was investigated in terms of length and directionality of neurite outgrowth. As fiber diameter decreased (from 100+ to 10 microm), the neurites tended to grow to a greater degree down the length of the fiber. The thinnest fibers (with diameters <20 microm) extended shorter neurites than the fibers with a wider diameter. Combining neurite length with guidance indicated that of the fiber diameters investigated, the optimal fiber diameter for neurite guidance was between 30 and 50 microm.

Animals↗

PubMed2004

Electrochemical and atomic force microscopy study of carbon surface modification via diazonium reduction in aqueous and acetonitrile solutions.

Electrochemical reduction of the diazonium salts of 4-nitrobenzene and 4-nitroazobenzene-4'- has been investigated in aqueous acid and acetonitrile media at carbon surfaces. Using pyrolyzed photoresist films as the substrate, we have examined the deposited films using electrochemistry and atomic force microscopy (AFM). Film thicknesses were measured by scratching through the film with an AFM tip. The procedure employed two AFM cantilevers with different lengths, located on the one device. When the shorter cantilever engages the surface in tapping mode, the longer cantilever (which is not resonating) imbeds into the surface with a constant force. For both modifiers and modification media, film thicknesses increase with deposition time to a limiting value. With equivalent modification conditions, films prepared in aqueous acid medium have lower limiting thicknesses than those prepared in acetonitrile. For nitrophenyl (NP) films, the same trends are found when calculating surface coverages from the charge associated with the reduction of surface -Ar-NO2 groups. Lower limiting film thicknesses and surface coverages for films prepared in aqueous conditions is attributed to growth of inherently more blocking films and is supported by examination of the response of the Fe(CN)6(3-/4-) couple at NP-modified surfaces. Combination of voltammetrically determined surface coverage and film thickness data yields a surface coverage of -Ar-NO2 groups of (2.5 +/- 0.5) x 10(-10) mol cm(-2) for a film thickness equivalent to a monolayer of NP groups.

Journal Article↗

PubMed1995

Studies on a new strategy for surface modification of polymeric biomaterials.

A new methodology to improve the hemocompatibility of polyurethane (medical grade Pellethane D-55) surfaces is reported. The approach is essentially based on a photochemical immobilization reaction. Two new conjugate molecules, compounds 2 and 3, were prepared. They consist of (i) dipyridamole, a well-known inhibitor of platelet activation, and a vasodilating drug with clinical application, for instance before and during pecutaneous transluminar coronary angioplasty (Dottering); and (ii) an aryl azide, a moiety that exhibits marked photoreactivity. In 2, the dipyridamole unit is directly linked to the aryl azide (via an ester bond), while a short spacer chain separates both units in 3. Upon irradiation of 2 or 3, adsorbed onto the polyurethane foil, the aryl azide is converted into a highly reactive species which reacts with a nucleophilic group on the polymer surface. In this way, the dipyridamole is covalently linked to the polymer. The underlying principle is also used in photoaffinity labeling, a well-known technique in biochemical studies on enzyme structure and function. From UV extinction experiments it could be deduced that the surface-density of immobilized 2 is 4.9 nmol/cm2. The surface density for 3 was 14.6 nmol/cm2. The surfaces were subjected to an in vitro thrombin generation assay. This assay gives a valuable impression about the hemocompatibility of artificial surfaces. These experiments revealed that the clotting times were substantially prolonged as a result of the photoimmobilization of dipyridamole. This was especially the case for immobilized 3. This effect cannot be readily explained. Possibly, the enhanced activity of immobilized 3 is due to the spacer chain. An alternative explanation is that the surface density is larger for 3 than for 2. In addition, the photomodified surfaces were incubated with platelet-rich blood plasma (37 degrees C, 30 min) and subsequently examined by scanning electron microscopy. The morphology of the blood platelets adhered to the surface also showed that hemocompatibility increased in the order untreated polyurethane < polyurethane with immobilized 2 < polyurethane with immobilized 3. Future work will concentrate on evaluation of the role of the spacer (length, hydrophilicity, etc.), as well as on the possible use of this approach with respect to the construction of biomaterials with improved in vivo biocompatibility, in particular hemocompatibility.

Adsorption↗

PubMed1996

Artificial cornea: surface modification of silicone rubber membrane by graft polymerization of pHEMA via glow discharge.

A method for producing various surfaces of silicone rubber membrane (SR) was developed in this study by grafting various amounts of poly(2-hydroxy ethyl methacrylate) (pHEMA) onto SR by plasma-induced grafted polymerization (PIP) as a homobifunctional membrane. The elemental composition and different carbon bindings on the surface of SR were examined by electron spectroscopy for chemical analysis with the amount of O1s/C1s being approximately 0.7 at 1 min, 60 W, 200 mTorr of Ar-plasma treatment. The peroxide group introduced on SR was measured via 1,1-diphenyl-2-picrylhydrazyl (DPPH) and the amount of 6.85 x 10(-8) mol cm-2 reached optimum value at 1 min of Ar-plasma treatment. After Ar-plasma treated SR, the peroxide group (33D peak) was introduced on the surface of SR by negative spectra of secondary ion mass spectroscopy analysis, whereas ester groups (72D peak) were observed for pHEMA-grafted SR. For the in vitro test, the influence of various surfaces of SR on attachment and growth of rabbit corneal epithelial cells (CEC) was studied by cell culture assay. These results indicated that 56-150 micrograms cm-2 of pHEMA grafted onto SR were suitable values for attachment and growth of CEC. On the contrary, the large grafted amounts (500-1650 micrograms cm-2) of pHEMA on SR were insufficient for attachment and growth of CEC. For the in vivo test, the migration of CEC from host cornea to implant was investigated by slit lamp microscopy. The experimental results indicated that SRs grafted with pHEMA were completely covered with CEC 3 weeks after implantation of the membranes into the host cornea. These results provide a valuable reference for developing an artificial cornea.

Animals↗

PubMed2005

Polysaccharide-protein surface modification of titanium via a layer-by-layer technique: characterization and cell behaviour aspects.

To improve the surface biocompatibility of titanium films, a layer-by-layer (LBL) self-assembly technique, based on the polyelectrolyte-mediated electrostatic adsorption of chitosan (Chi) and gelatin (Gel), was used leading to the formation of multilayers on the titanium thin film surfaces. The film growth was initialized by deposition of one layer of positively charged poly(ethylene imine) (PEI). Then the thin film was formed by the alternate deposition of negatively charged Gel and positively charged Chi utilizing electrostatic interactions. The LBL film growth was monitored by several techniques. The chemical composition, surface topography as well as wettability were investigated by using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), confocal laser scanning microscopy (CLSM) and water contact angle measurement, respectively. Quantitative XPS analysis showed the alternative change of C/N ratio after four sequential cycles coating of Ti/PEI/Gel/Chi/Gel, which indicated the discrete layer structure of coatings. Uncoated titanium (control sample) displayed a smooth surface morphology (root mean square (RMS) roughness was around 2.5 nm). A full coverage of coating with Gel/Chi layers was achieved on the titanium surface only after the deposition layers of PEI/(Gel/Chi)2. The PEI/Gel/(Chi/Gel)3 layer displayed a rough surface morphology with a tree-like structure (RMS roughness is around 82 nm). These results showed that titanium films could be modified with Chi/Gel which may affect the biocompatibility of the modified titanium films. To confirm this hypothesis, cell proliferation and cell viability of osteoblasts on LBL-modified titanium films as well as control samples were investigated in vitro. The proliferation of osteoblasts on modified titanium films was found to be greater than that on control (p<0.05) after 1 and 7 days culture, respectively. Cell viability measurement showed that the Chi/Gel-modified films have higher cell viability (p<0.05) than the control. These data suggest that Chi/Gel were successfully employed to surface engineer titanium via LBL technique, and enhanced its cell biocompatibility. The approach presented here may be exploited for fabrication of titanium-based implant surfaces.

Adsorption↗

PubMed1996

Maintenance of implants: an in vitro study of titanium implant surface modifications subsequent to the application of different prophylaxis procedures.

The aim of the present study was to evaluate surface alterations on titanium implant necks subsequent to different prophylaxis procedures. Fifty ITI implants were utilized. Forty implants were treated with 10 different prophylaxis procedures (ultrasonic scaler, plastic tip ultrasonic scaler, stainless steel curette, titanium curette, teflon curette, air powered system, abrasive rubber cups, polishing rubber cup and brush), and 10 implants were left as untreated controls. Surface alterations were studied on an area of 1 mm x 0.9 mm and quantified using optical microscopic, SEM and laser prophylometer analysis. The use of laser prophylometer provided an objective criterion for evaluation, expressing implant neck surface alterations in numeric values in terms of two roughness indexes, Ra and Rz. The results showed that, in comparison with the controls (Ra = 0.50; Rz = 3.98) the procedures investigated could be divided into 3 main groups: 1) Methods which altered the implant neck surface producing increased roughness (Ra = 0.68-2.08; Rz = 4.68-11.92); 2) Methods which left the implant neck surface unaltered (Ra = 0.44-0.57; Rz = 0.42-3.46); 3) Methods resulting in a smoothening of the implant neck surface (Ra = 0.36; Rz = 2.15). Group 1 included procedures that should be avoided. However, it appeared safe to apply the procedures of groups 2 and 3. To confirm these results, it will be necessary to evaluate the plaque- and calculus-removing efficacy from titanium neck implant surfaces in vivo.

Air↗

PubMed1982

Surface modification of Beckman Ultra-Clear centrifuge tubes for density gradient centrifugation of lipoproteins.

A simple procedure for coating the interior surface of Beckman Ultra-Clear centrifuge tubes with polyvinyl alcohol is described. The coated tubes are wettable and allow salt solutions to gravity-feed down their sides. This modification of the tubes permits the performance of previously developed density gradient and uniform density ultracentrifugation procedures for lipoprotein fractionation.

Centrifugation, Density Gradient↗