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Results for “surface modification”

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At least 1,027 records · Page 57Linked to original sources

PubMed2001

A comparison of the adhesion of mammalian cells and Staphylococcus epidermidis on fibronectin-modified polymer surfaces.

The modification of polymer surfaces to mimic the extracellular matrix, and therefore, stimulate cell growth via receptor-mediated interactions, is one approach used to promote the integration of tissue-engineering scaffolds and biomaterials into the body. However, by optimizing surfaces for tissue integration it is likely that bacterial adhesion may also be affected, resulting in a greater risk of biomaterial-related infection. This could be detrimental to both the implant and the patient because biomaterial related infections are particularly resistant to host defenses and antibiotics. In this study, we analyzed the adhesion of a Staphylococcus epidermidis clinical isolate and 3T3 rat fibroblasts to tissue culture plastic coated with varying concentrations of fibronectin (Fn). Bacterial adhesion was always lower than tissue culture plastic and appeared to decrease with increasing Fn concentrations. Mammalian cell adhesion to Fn exceeded adhesion to tissue culture plastic but did not differ significantly over the range of protein concentrations or between 1 and 4 h of incubation. In most cases, the total surface coverage did not vary with time or Fn concentration, indicating that maximal cell adhesion and spreading occurred rapidly and at low protein concentrations. This study suggests that, by controlling the density of proteins or ligands on a surface, we can potentially optimize mammalian cell adhesion without stimulating bacterial adhesion, hence reducing the likelihood of infection.

3T3 Cells↗

PubMed2002

Adhesion between poly(ethylene-co-vinyl alcohol) (EVA) and titanium.

Lap shear adhesive strength between titanium and various kinds of commercial polymers was evaluated. Among them, poly(ethylene-co-vinyl alcohol) (EVA) showed the highest strength. The results of electron spectroscopy for chemical analysis and the contact angle to water indicated that the high adhesive strength of EVA might be due to its high hydrophilicity. Water resistance of adhesion by water immersing at 37 degrees C was investigated. In the case of polyurethane-titanium, the adhesive strength decreased immediately. In contrast, EVA-titanium kept its initial adhesive strength for at least up to 1 month. It was confirmed that surface modification of titanium by hydrogen peroxide enhanced the adhesive and peeling strength. It was based on not only an increase in surface adhesive area but also an increase in the hydrophilicity of titanium by the production of Ti-OH.

Adhesiveness↗

PubMed2006

Influence of physicochemical properties of laser-modified polystyrene on bovine serum albumin adsorption and rat C6 glioma cell behavior.

Biomaterial surface modification is an efficient way of improving cell-material interactions. In this study, sub-micrometer laser-induced periodic surface structures (LIPSS) were produced on polystyrene by laser irradiation. FT-IR analysis confirmed that this treatment also led to surface oxidation and anisotropic orientation of the produced carbonyl groups. As a consequence, the surface energy of the laser-treated polystyrene was 1.45 times that of the untreated polystyrene, as measured by contact-angle goniometry. Protein adsorption and rat C6 glioma cell behavior on the two substrates were investigated, showing that the changed physicochemical properties of laser-modified polystyrene surface led to an increase in the quantity of adsorbed bovine serum albumin and significantly affected the behavior of rat C6 glioma cells. In the early stages of cell spreading, cells explored their microenvironment using filopodium as the main sensor. Moreover, cells actively aligned themselves along the direction of LIPSS gradually and cell attachment and proliferation were significantly enhanced.

Adsorption↗

PubMed2005

Corrosion resistance and bioactivity of titanium after surface treatment by three different methods: ion implantation, alkaline treatment and anodic oxidation.

The paper compares the effects of various surface modifications, ion implantation, alkaline treatment and anodic oxidation, upon the corrosion resistance and bioactivity of titanium. The chemical composition of the surface layers thus produced was determined by XPS, SIMS and EDS coupled with SEM. The structure of the layers was examined by TEM, and their phase composition by XRD. The corrosion resistance was determined by electrochemical methods after the samples were exposed to the test conditions for 13 h. The bioactivity of titanium was evaluated in a simulated body fluid at a temperature of 37 degrees C after various exposure time.

Electrodes↗

PubMed2005

Characterization of the mechanical properties of polymeric chromatographic particles by micromanipulation.

Chromatographic particles should not possess only desirable surface chemical properties but also mechanical properties. The latter determine the deformation of the particles under hydrodynamic conditions of packed beds and further the pressure drop. Understanding the mechanical properties of chromatographic particles is essential to successful design and operation of such processing equipment. The mechanical properties of single chromatographic particles made of different formulations and with different surface modifications were characterized by a novel micromanipulation technique. The principle of this technique is to compress single particles between two parallel surfaces. The force being imposed on the particles and their deformation under compression are measured simultaneously. The particles range from 30 to 300 microm, depending on their formulation. 10-30 particles from each sample were compressed up to a particle deformation of 70% in order to get statistically representative data. Particles for hydrophobic interaction chromatography were proved more stable than resins for ion exchange or gel filtration. The difference is remarkable in dry state and is less in wet state. Water seems to "level out" the differences in mechanical stability of resins. The stability seems to be also dependent on the speed of water release out of the resins.

Algorithms↗

PubMed2003

A preliminary study of modification of gait in real-time using surface electromyography.

Modification of abnormal gait was attempted in real-time using a surface electromyography-based protocol to teach recruitment of the anterior tibialis at the correct time in the gait cycle. Two children diagnosed with cerebral palsy were able to learn volitional control of the anterior tibialis as demonstrated by improved clearance of the toe on the swing phase of the gait and newly learned ability to recruit and relax the anterior tibialis. The children were able to walk with the new gait pattern and reproduce the old one at will. Implications for future research in this area are discussed.

Biofeedback, Psychology↗

PubMed2003

Some soft tissue characteristics at implant abutments with different surface topography. A study in humans.

BACKGROUND: : If an implant with a rough surface is exposed to the oral cavity, it may accumulate greater amounts of plaque than a smooth surface, which may lead to severe problems with mucositis and peri-implantitis. The purpose of the present paper was to investigate the early inflammatory response to mucosa-penetrating abutments prepared with varying surface roughness. METHODS: : Nine patients had all five of their original abutments exchanged to test abutments for a 4-week period. The test abutments were prepared with five different roughnesses. The surface roughness was measured with an optical profilometer. At the end of the test period, clinical evaluation was performed; the health of the surrounding mucosa, the amount of accumulated plaque and marginal bleeding were registered. One biopsy was taken from each test abutment. Qualitative and quantitative histological evaluations were performed. RESULTS: : There was a statistically significant difference between patients regarding the amount of accumulated plaque on the abutment surfaces and inflammatory cells, but no difference between the surface modifications in relation to plaque accumulation or number of inflammatory cells. CONCLUSION: : No relation was found between inflammatory response and abutment surface roughness after an evaluation time of 4 weeks in a human test model.

Aluminum Oxide↗

PubMed1999

UDP-GlcNAc 2-epimerase: a regulator of cell surface sialylation.

Modification of cell surface molecules with sialic acid is crucial for their function in many biological processes, including cell adhesion and signal transduction. Uridine diphosphate-N-acetylglucosamine 2-epimerase (UDP-GlcNAc 2-epimerase) is an enzyme that catalyzes an early, rate-limiting step in the sialic acid biosynthetic pathway. UDP-GlcNAc 2-epimerase was found to be a major determinant of cell surface sialylation in human hematopoietic cell lines and a critical regulator of the function of specific cell surface adhesion molecules.

Animals↗

PubMed2005

Direct microcontact printing of oligonucleotides for biochip applications.

BACKGROUND: A critical step in the fabrication of biochips is the controlled placement of probes molecules on solid surfaces. This is currently performed by sequential deposition of probes on a target surface with split or solid pins. In this article, we present a cost-effective procedure namely microcontact printing using stamps, for a parallel deposition of probes applicable for manufacturing biochips. RESULTS: Contrary to a previous work, we showed that the stamps tailored with an elastomeric poly(dimethylsiloxane) material did not require any surface modification to be able to adsorb oligonucleotides or PCR products. The adsorbed DNA molecules are subsequently printed efficiently on a target surface with high sub-micron resolution. Secondly, we showed that successive stamping is characterized by an exponential decay of the amount of transferred DNA molecules to the surface up the 4th print, then followed by a second regime of transfer that was dependent on the contact time and which resulted in reduced quality of the features. Thus, while consecutive stamping was possible, this procedure turned out to be less reproducible and more time consuming than simply re-inking the stamps between each print. Thirdly, we showed that the hybridization signals on arrays made by microcontact printing were 5 to 10-times higher than those made by conventional spotting methods. Finally, we demonstrated the validity of this microcontact printing method in manufacturing oligonucleotides arrays for mutations recognition in a yeast gene. CONCLUSION: The microcontact printing can be considered as a new potential technology platform to pattern DNA microarrays that may have significant advantages over the conventional spotting technologies as it is easy to implement, it uses low cost material to make the stamp, and the arrays made by this technology are 10-times more sensitive in term of hybridization signals than those manufactured by conventional spotting technology.

Journal Article↗

PubMed1998

Platelet and cell interactions on gold sputter-deposited polymeric surfaces.

Surface treatment as gold sputter-deposited treatment onto various polymeric surfaces has been investigated to improve the cell-, tissue- and blood-compatibility. Surface treated samples were characterized by measurement of contact angle goniometer and electron spectroscopy for chemical analysis (ESCA). The contact angles on the gold-coated polymeric surfaces decreased from 95-65 degrees to around 50 degrees, i.e., increased hydrophilicity due to incorporation of gold thin layer. From the results of ESCA analysis of the modified polymeric surfaces, surface modification by the gold-sputter method was successfully performed. Morphology of the adhered platelets on the gold-coated polymeric surfaces showed lesser activating than control, and the number of adhered platelets surface modified samples decreased with decreasing water contact angle. Fibroblast cell adhesion and growth on the gold-coated polymeric surfaces were more active than those of control. It seems that surface wettability and surface chemistry of gold play important roles for platelet adhesion and cell adhesion, spreading and growth.

3T3 Cells↗

PubMed2001

Effects of a modified sandblasting surface treatment on topographic and chemical properties of titanium surface.

A modified sandblasting surface treatment (a noncoating, roughening surface modification of dental implants) has been developed that will overcome the defects of conventional coating techniques. To verify the feasibility and reliability of this method at the chemical and topographic levels, scanning electron microscopy, x-ray diffraction, and a titanium ion releasing test were used; the topography of titanium surface, the embedding of sandblasting particles, nonpollution of heteroelements, and anticorrosiveness of titanium were criteria. Results showed that the rough surface created by sandblast was rather irregular, full of sharp tips and many embedded sandblast particles, and its corrosive rate was increased. These characteristics were modified by oxalic acid attack; the contour of the rough surface became more regular and round, the embedded particles and the heteroelement pollution were thoroughly removed, and the Ti corrosive rate decreased dramatically. Oxalic acid attack modification also created numerous secondary micropores (2.0-micron diameter) on the basis of sandblasted surface macrotexture. This modified sandblasting surface treatment is feasible and reliable to apply to dental implants and does not decrease the biocompatibility of titanium.

Aluminum Oxide↗

PubMed1997

Influence of surface hydrophilic/hydrophobic balance on enzyme properties.

Two different enzyme surface modifications were carried out in order to alter the protein hydrophilic/hydrophobic balance in opposite directions and to observe the effects induced on enzyme properties. First, a novel chemoenzymatic glycosylation method was applied, which resulted in a higher enzyme surface hydrophilic character. Then, an amphiphilic polymer, PEG, was bound to the enzymes by chemical means, and it brought about an increase in the global hydrophobic character. Two different enzymes, alpha-chymotrypsin and Candida rugosa lipase, were studied, and in all cases, several degrees of modification were obtained. Then, the modified biocatalysts were thoroughly investigated, and the influence of the variation of surface hydrophilic/hydrophobic balance on hydrolytic activity, hydrolysis kinetic parameters, synthetic activity and thermal stability was assessed.

Animals↗

PubMed1997

Use of surface-modifying macromolecules to enhance the biostability of segmented polyurethanes.

Polyurethanes are widely used as biomaterials for medical implants because of their excellent mechanical properties and moderate biocompatibility. However, the demand for more bioresistant and biocompatible polyurethanes to meet the needs of long-term implant devices still remains an important issue. Since most biological interactions with materials occur at the interface, a significant number of studies for improving the biocompatibility of polyurethanes have concentrated on surface modification. It is well known that additives used in polymeric materials as processing aids, mold releasing agents, antioxidants, etc., migrate to the surface and change the surface properties of the material. Under certain conditions polymeric additives may also migrate toward surfaces. This study describes two fluorine-containing, surface-modifying macromolecules (SMMs) that have been evaluated for their ability to inhibit polyurethane degradation. These materials actively migrate to the upper surface of a material film when they are mixed with a base polymeric materia. Contact angle measurements for the mixture of SMM with base polyurethane indicate that the surface becomes more hydrophobic after adding the SMMs, while X-ray photoelectron spectroscopy analysis shows an enrichment of fluorine on the polymer surfaces. Differential scanning calorimetry thermograms indicate that the micro-structure, as defined by the thermal transitions of the base polymer, are not altered by the addition of SMMs. Enzyme-induced biodegradation tests exhibit a significant reduction of polyurethane degradation in the presence of these surface-resident materials. The results indicate that the SMMs have the potential to resist hydrolytic degradation mediated by lysosomal enzymes while generating a surface chemistry on the native elastomer which is similar in nature to that of a fluoropolymer, e.g., Teflon.

Absorptiometry, Photon↗

PubMed1999

Transient poration and cell surface receptor removal from human lymphocytes in vitro by 1 MHz ultrasound.

The study objective was to gain insight into ultrasound-induced, sub-lytic cell surface modifications. Two primary hypotheses were tested by flow cytometric methods; viz., sonication will: 1. remove all or part of a specific cell surface marker in lymphocytes surviving insonation, and 2. induce transient pores in the cell membranes of some surviving cells. RPMI 1788 human lymphocytes were exposed in vitro to 1-MHz, continuous-wave ultrasound (approximately 8 W/cm2 ISP) for 30 s, which lysed approximately 50% of the cells. Insonation: 1. altered cell morphology, increasing the population of cells of reduced size but high structure (designated as population R2), many of which were nonviable, and diminishing the population of cells of large size and high structure (designated as population R1), most of which were viable, 2. diminished the fluorescence signal from the pan B lymphocyte marker CD19 in populations R1 and R2 to equivalent extents, and 3. increased by approximately 7-fold the number of transiently permeabilized cells in R1, as evidenced by simultaneous uptake of propidium iodide and fluorescein diacetate. The results indicate that ultrasound-induced CD19 removal from R1 cells can occur without accompanying gross membrane loss. The cell morphology/mortality shifts indicate that the ultrasound-induced morphological change is associated with lethal membrane poration, suggesting that the diminished CD19 fluorescence signal from insonated R2 cells arises partly by simultaneous loss of membrane fragments, CD19 and cytoplasm.

Antigens, CD19↗

PubMed1999

Improvement of haemocompatibility of metallic stents by polymer coating.

An alternative to open heart surgery in treating arterial diseases causing restricted blood flow is the implantation of intracoronary metallic stents. In spite of the advances in implantation and in spite of the excellent mechanical properties of metallic stents, there are still limitations because of the thrombogenicity of the metal. We have, hence, directed our attention to the coating of metallic stents with an ultrathin polymer layer by chemical vapor deposition (CVD) polymerization of 2-chloroparacyclophan. In a second step of surface modification the poly(2-chloroparaxylylene) layer is modified by treatment with a sulfur dioxide plasma in order to obtain a more hydrophilic surface with new functional groups. The results demonstrate the stable polymer coating of the stents and the improvement of haemocompatibility after treatment with sulfur dioxide plasma. Platelet adhesion is decreased from 85% for the metal surface to 20% for the CVD-coated and sulfur-dioxide-plasma treated surface.

Journal Article↗

PubMed1992

Flow Cytometric Analysis of Rhodamine 123 Fluorescence during Modulation of the Membrane Potential in Plant Mitochondria.

The fluorescent dye rhodamine 123, which selectively accumulates in mitochondria based on the membrane potential, was used with flow cytometry to evaluate variations in activity of mitochondria isolated from plant tissues. In the presence of succinate and ATP, potato (Solanum tuberosum L.) tuber mitochondrial activity was affected by metabolic inhibitors and compounds that modify the membrane potential. The more uniform the mitochondrial population, the higher the observed membrane potential. The reactive population corresponds to the proportion of intact mitochondria (94-97%) defined by classic methods. Changes in the light-scattering properties are more related to internal modifications affecting the inner membrane-matrix system of the mitochondria during metabolic modulation than to specific volume change or outer membrane surface modifications. We tested our approach using an Arum maculatum preparation that contains three different types of mitochondria and demonstrated the validity of the light-scatter measurements to distinguish the alpha, beta, and [ill] mitochondria and to measure their ability to built up a membrane potential in the presence of succinate. These results demonstrate clearly that flow cytometric techniques using rhodamine 123 can be employed to study the activity in isolated plant mitochondria.

Journal Article↗

PubMed2006

Possible binding sites for biotin stabilized water soluble Ag nanoparticles: an experimental and theoretical study.

The evolution of Ag nanoparticles by photochemical reduction method and the effect of biotin on their UV-Visible absorption spectrum were studied. Surface modification studies were carried out on chemically reduced Ag nanoparticles. ATR-FTIR studies showed that the biotin molecules bind with the surface of Ag nanoparticles through the oxygen of the carboxylate group. Theoretical calculations were carried out on the structure of the biotin and the silver complex of biotin (biotin(-)-Ag+) by optimizing their structures using density functional calculations with the B3LYP method using the LANL2DZ basis set. Theoretical calculations and experimental evidence favors a preferential binding of biotin molecule to Ag nanoparticles through the carboxylate group.

Binding Sites↗

PubMed2000

Silica nanoparticles modified with aminosilanes as carriers for plasmid DNA.

We synthesised silica nanoparticles (SiNP) with covalently linked cationic surface modifications and demonstrated their ability to electrostatically bind, condense and protect plasmid DNA. These particles might be utilised as DNA carriers for gene delivery. All nanoparticles were sized between 10 and 100 nm and displayed surface charge potentials from +7 to +31 mV at pH 7.4. They were produced by modification of commercially available (IPAST) or in-house synthesised silica particles with either N-(2-aminoethyl)-3-aminopropyltrimethoxysilane or N-(6-aminohexyl)-3-aminopropyltrimethoxysilane. All particles formed complexes with pCMVbeta plasmid DNA as evidenced by ratio dependent retardation of DNA in the agarose gel and co-sedimentation of soluble DNA with nanoparticles. High salt and alkaline pH did inhibit complex formation. Absorption onto the particles also decreased the hydrodynamic dimensions of plasmid DNA as shown by photon correlation spectroscopy. Complexes formed in water at a w/w ratio of Si26H:DNA (pCMVbeta) of 300 were smallest with a mean hydrodynamic diameter of 83 nm. For effective condensation a w/w ratio of Si26H:DNA of 30 was sufficient. Further, the absorbed DNA was protected from enzymatic degradation by DNase I.

DNA↗