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At least 451 records · Page 25Linked to original sources
PubMed2004

Surface modification using photocrosslinkable chitosan for improving hemocompatibility.

Immobilization of the anticoagulative or antithrombogenic biomolecule has been considered as one of the important methods to improve the blood compatibility of artificial biomaterials. In this study, a novel immobilization reaction scheme was utilized to incorporate O-butyrylchitosan (OBCS) onto the activated glass surface with an aim to develop an anticoagulative substrate. Activation of the glass surface was carried out by silanization and then OBCS was grafted to the silanized surface via a radiation grafting technique. The OBCS-grafted glass surfaces were characterized by electron spectroscopy for chemical analysis (ESCA) and atomic force microscopy (AFM). The blood compatibility of the OBCS-grafted glass was evaluated by platelet rich plasma (PRP) contacting experiments and protein adsorption experiments in vitro. These results have demonstrated that the surface with immobilized OBCS shows much less platelet adhesive and fibrinogen adsorption compared to the control surface. Therefore, the novel reaction scheme proposed here is very promising for future development of an anticoagulative glass substrate.

Blood Coagulation↗
PubMed2001

Surface modification of mesoporous, macroporous, and amorphous silica with catalytically active polyoxometalate clusters.

Transition-metal-substituted polyoxometalates (TMSP) of the type [MII(H2O)PW11O39]5- (M = Co, Zn) and [SiW9O37(CoII(H2O))3]10- have been chemically anchored to modified macroporous (400 nm pores), mesoporous (2.8 nm pores), and amorphous silica surfaces. The materials were characterized by solid-state 31P MAS NMR, UV-vis, FT-IR spectroscopy, and N2 adsorption experiments to verify cluster attachment and the structure of the TMSP on the support. On the basis of the spectroscopic evidence, clusters were attached datively to the surface, and the integrity of the [CoPW11] cluster was maintained for nonaqueous impregnation with TBA5[CoPW11]; partial degradation of the cluster occurred when it was impregnated from aqueous solution using the K5[CoPW11] salt. Both the amine surface groups and the cobalt centers in the clusters were found to be necessary to prevent cluster loss during washing or reaction processes. The catalytic activities of the supported TMSP clusters were tested by the epoxidation of cyclohexene to cyclohexene oxide in the presence of isobutyraldehyde. The percent conversion of the substrate and the amount of product formed per unit time were similar for [CoPW11] clusters on each of the three silica supports, but slightly lower than for purely homogeneous reactions. [SiW9Co3] clusters with three available cobalt centers exhibited higher catalytic activity with nearly identical performance on a silica support or in homogeneous solution.

Journal Article↗
PubMed1983

Surface modification and characterization of some commonly used catheter materials. II. Friction characterization.

The effects of the modification of polystyrene (PS), polyethylene (PE), poly(vinyl chloride) (PVC), silicone rubber (SR), and fluorinated ethylene propylene (FEP) copolymer by radio frequency glow discharge in a helium environment were presented in part I. The hydrated polymer surfaces were characterized by XPS, SEM, visual microscopy, and by contact angle measurements. In general, exposure of the polymers to RFGD produced an oxidized hydrophilic surface, yet the roughness of the surface was unaltered by the relatively mild plasma conditions used. In this article, the frictional behavior of oxidized and unoxidized SR, PE, and FEP in distilled water, isotonic saline, and blood plasma environments is examined experimentally. The results are discussed in relation to the properties generally believed to affect frictional phenomena and to the surface properties as determined in part I. Results indicate that RFGD-treated SR generates less friction than untreated SR when dragged across all untreated and treated polymer surfaces, whether the medium is distilled water or an isotonic saline solution. Friction is consistently lower in a blood plasma medium between all surfaces investigated, most probably because of the presence of adsorbed proteins at the polymer interfaces.

Biocompatible Materials↗
PubMed1996

Synthesis of phenylazido-derivatized substances and photochemical surface modification to immobilize functional groups.

Phenylazido-derivatized low-molecular-weight substances and copolymers containing hydrocarbon- or fluorocarbonalkyl group, sulfonato or amino group, and hydroxyl group were prepared. Upon coating and subsequent ultraviolet (UV) light irradiation, covalent fixation of these substances or copolymers took place only at irradiated portions of polymer surfaces, providing a hydrophobic, ionic, or hydrophilic nature. These were verified with electron spectroscopy for chemical analysis (ESCA) spectra and water contact-angle measurement. Endothelial cells adhered on photochemically modified surfaces which have alkyl, sulfonato, or amino groups on their surfaces, whereas little adhesion occurred on a hydroxyl group-bearing hydrogellike surface. When UV light was irradiated through a photomask on the polymer surfaces, patterned and microprocessed surfaces having cell-adhering and nonadhering regions were obtained. The potential application of this photochemical surface processing method in biomedical engineering is discussed.

Adsorption↗
PubMed1982

Surface modifications in the platelets of a patient with alpha-N-acetyl-D-galactosamine residues, the Tn-syndrome.

The Tn-syndrome is an acquired disorder characterized by the polyagglutination of blood cells and the pathological exposure of alpha-N-acetyl-D-galactosamine residues (Tn-antigen) at the cell surface. We now report studies on the platelet of a patient (Ba.) of which 81% reacted positively with a fluorescein conjugate of Helix pomatia agglutinin (HPA). The surface proteins of Ba. platelets were labeled with 125I by the lactoperoxidase-catalyzed procedure; single and two-dimensional electrophoresis on sodium dodecyl sulfate (SDS)-polyacrylamide gels was followed by autoradiography that revealed normal 125I-labeling of the major membrane glycoproteins (GP) but that GP Ib had a faster than normal migration. the abnormal GP Ib of Ba. platelets was strongly labeled when platelet suspensions were treated sequentially with neuraminidase, galactose oxidase, and sodium [3H]borohydride. Unlike the GP Ib of normal human platelets, it was also strongly labeled when Ba. platelets were treated with galactose oxidase and sodium [3H]borohydride alone. Both the alloantigen, PlA1, and quinidine-dependent antibody receptor activity were normally expressed by Ba. platelets, which also bound a monoclonal antibody (AN51) to GP Ib. Analysis of Ba. platelets by crossed immunoelectrophoresis using a rabbit anti-human platelet antibody preparation revealed the presence of an immunoprecipitate in the GP Ib position that had an abnormal appearance and migration in the second dimension. An altered position of the precipitate given by Factor VIIIR:Ag was also noted. Incorporation of HPA into the agarose gel during the first dimension electrophoresis resulted in the specific precipitation of the abnormal GP Ib of Ba. platelets. Our studies show that circulating Tn-platelets contain GP Ib with a modified oligosaccharide chain structure responsible for the platelet expression of Tn-antigen activity.

Acetylgalactosamine↗
PubMed2005

Surface modification of mechanochemically activated kaolinites by selective leaching.

Low- and high-defect kaolinites mechanochemically activated for different periods of time have been treated with sulfuric acid solution. These modified materials were analyzed using a combination of X-ray diffraction, thermogravimetry, chemical analysis, diffuse reflectance Fourier transform infrared spectroscopy, as well as specific surface area and pore size distribution measurements. In addition to the mechanochemically amorphized part, the disordered and the adequately distorted phases also reacted with sulfuric acid. The specific surface areas of the leached samples of the partially or the completely amorphized materials were found to be greater than those of the thermally amorphized ones. The acid treatment results in a greater total pore volume for the partially amorphized materials than for the totally amorphized mineral. The partially amorphized high-defect kaolinite was proved to be more soluble than the low-defect kaolinite under similar conditions.

Journal Article↗
PubMed1985

Low mobility T cells in the peripheral blood of cancer patients: surface modification and mobility.

To elucidate how low-mobility T cells emerge in the peripheral blood of cancer patients, lymphocytes from normal individuals were treated with cancer patients' plasma, immunosuppressive (IS) substance with or without interleukin-2, or neuraminidase. A delay in cell mobility was induced by IS substance and neuraminidase treatments, which degrade the cell surface charge. Compared to the normal mobility pattern of lymphocytes, patterns induced by these treatments were characterized by a general shift of the fast cell peak to the left side. These patterns were different from those of cancer patients in terms of the inverse relationship between slow and fast peaks. These results indicate that, though humoral factors in the peripheral blood of cancer patients take a partial role, other mechanisms might operate to induce the characteristic mobility pattern of lymphocytes. One of the possibilities, the emerging of a special T cell subset recruited from the thymus, is discussed.

Cell Movement↗
PubMed2001

Surface modification of polyhydroxyalkanoate films and their interaction with human fibroblasts.

A poly(3-hydroxybutylate-co-hydroxyvalerate) (PHA) film containing 34 mol.% 3-hydroxyvalerate (Biopol D600P) was prepared by the solvent cast method using a 10 wt.% chloroform solution of PHA. The PHA film was exposed to an oxygen plasma glow discharge to produce peroxides on its surfaces. These peroxides were then used as catalysts for the polymerization of acrylic acid (AA) in order to prepare carboxyl group-introduced PHA (PHA-C). Insulin-immobilized PHA was prepared using the coupling reaction of PU-C with insulin. The surface-modified PHAs were then characterized by attenuated total reflection Fourier transform infrared spectroscopy, electron spectroscopy for chemical analysis, and a contact angle goniometer. The amounts of insulin directly coupled to the carboxyl groups on PHA-C and coupled to the terminus amino groups of the grafted polyethylene oxide were 2.9 and 0.8 microg cm(-2), respectively. The PHA water contact angle (75 degrees ) decreased with AA grafting (33 degrees ) and insulin immobilization (31 degrees ), thereby exhibiting the increased hydrophilicity of the modified PHAs. When compared with PHA and PHA-C, the proliferation of human fibroblasts in the presence of serum was significantly accelerated on the insulin-immobilized PHAs.

Acrylates↗
PubMed1997

Electrochemical and surface modifications on N+-ion-implanted 316 L stainless steel.

The effect of nitrogen-ion implantation on the electrochemical behaviour of 316 L stainless steel in a simulated physiological solution (HBSS-Hank's Balanced Salt Solution) was studied by open-circuit potential versus time and cyclic polarization techniques, with the aim of characterizing the surfaces and choosing the best nitrogen-ion fluence. Three fluences (10(15), 10(16) and 10(17) ions/cm2) were used. The 10(16) ions/cm2 N+ fluence improves the corrosion resistance of the 316 L stainless steel.

Journal Article↗
PubMed2005

The regulation of expanded human nasal chondrocyte re-differentiation capacity by substrate composition and gas plasma surface modification.

Optimizing re-differentiation of clinically relevant cell sources on biomaterial substrates in serum containing (S+) and serum-free (SF) media is a key consideration in scaffold-based articular cartilage repair strategies. We investigated whether the adhesion and post-expansion re-differentiation of human chondrocytes could be regulated by controlled changes in substrate surface chemistry and composition in S+ and SF media following gas plasma (GP) treatment. Expanded human nasal chondrocytes were plated on gas plasma treated (GP+) or untreated (GP-) poly(ethylene glycol)-terephthalate-poly(butylene terephthalate) (PEGT/PBT) block co-polymer films with two compositions (low or high PEG content). Total cellularity, cell morphology and immunofluorescent staining of vitronectin (VN) and fibronectin (FN) integrin receptors were evaluated, while post-expansion chondrogenic phenotype was assessed by collagen types I and II mRNA expression. We observed a direct relationship between cellularity, cell morphology and re-differentiation potential. Substrates supporting high cell adhesion and a spread morphology (i.e. GP+ and low PEG content films), resulted in a significantly greater number of cells expressing alpha5beta1 FN to alpha(V)beta3 VN integrin receptors, concomitant with reduced collagen type II/ImRNA gene expression. Substrates supporting low cell adhesion and a spherical morphology (GP- and high PEG content films) promoted chondrocyte re-differentiation indicated by high collagen type II/I gene expression and a low percentage of alpha5beta1 FN integrin expressing cells. This study demonstrates that cell-substrate interactions via alpha5beta1 FN integrin mediated receptors negatively impacts expanded human nasal chondrocyte re-differentiation capacity. GP treatment promotes cell adhesion in S+ media but reverses the ability of low PEG content PEGT/PBT substrates to maintain chondrocyte phenotype. We suggest alternative cell immobilization techniques to GP are necessary for clinical application in articular cartilage repair.

Adult↗
PubMed2005

Dual-surface modification of the tobacco mosaic virus.

The protein shell of the tobacco mosaic virus (TMV) provides a robust and practical tubelike scaffold for the preparation of nanoscale materials. To expand the range of applications for which the capsid can be used, two synthetic strategies have been developed for the attachment of new functionality to either the exterior or the interior surface of the virus. The first of these is accomplished using a highly efficient diazonium coupling/oxime formation sequence, which installs >2000 copies of a material component on the capsid exterior. Alternatively, the inner cavity of the tube can be modified by attaching amines to glutamic acid side chains through a carbodiimide coupling reaction. Both of these reactions have been demonstrated for a series of substrates, including biotin, chromophores, and crown ethers. Through the attachment of PEG polymers to the capsid exterior, organic-soluble TMV rods have been prepared. Finally, the orthogonality of these reactions has been demonstrated by installing different functional groups on the exterior and interior surfaces of the same capsid assemblies.

Capsid↗
PubMed2005

Surface modification of pure titanium by plasma exposure and its bonding to resin.

The purpose of this study was to investigate the effects on shear bond strength to resin after pure titanium (Ti) was exposed to plasma under different kinds of gas atmosphere. Polished Ti samples were treated using a plasma exposure apparatus in gas atmospheres of air, CO2, and C3F8. Surface analysis of Ti exposed to plasma was achieved through surface free energy and XPS measurements. The Ti sample was bonded with adhesive resin (4-META, MAC-10, HEMA, MDP, VBATDT) to a stainless steel piece. After which, shearing adhesion test was done. It was observed that plasma exposure in a specific gas atmosphere in regulated the bonding strength of titanium surface to resin. Based on the results of this study, we concluded that plasma exposure was a useful surface treatment method for dental practices.

Air↗
PubMed1999

Bioceramics surface modification by means of osteoclasts in culture.

The specific objectives of this study was: (I) to investigate the effect of various biomedical ceramics such as tricalcium phosphate (TCP), hydroxyapatite (HA), and aluminum-calcium-phosphorous oxide (ALCAP) on the adherence and viability of mice osteoclasts (OT) in vitro, and (II) to evaluate the role of OT that might have on the surfaces of such bioceramics. The OT cells were isolated from adult male mice and seeded at a density of 5 x 10(5) cells/well according to standard laboratory procedures. Cells were plated in each micrometer-well pretreated with ceramic capsules (HA, TCP and ALCAP) and buffered control. At the end of 1, 2, 3 and 5 days, the viability and cell number of OT were determined using an established assay. Cell number was determined in control wells with known number of cells, and a standard curve was generated by plotting absorbency units versus cell number. Biochemical analysis was performed on the aliquots obtained from the experimental and control wells at the end of each phase of the investigation. The data from this experiment suggest that: (I) OT are capable of adhering to the surface of HA, TCP and ALCAP in an in vitro environment for over a 5-day period. (II) Long-term incubation of ceramic capsules with OT revealed that the cells experienced gradual disassociation phenomenon with a greater numbers of cell detachments seen in the ALCAP contained wells. (III) SEM analysis of representative capsules demonstrated that there was an increase in the number of micro/macropores on the surface of the materials after contacting a cellular environment. This observation suggest that the material surface has been modified (TCP > HA = ALCAP). Information obtained from this study provided new insights on the interrelationship between bioceramics and the possible OT response during chronic inflammation at the site of implantation.

Aluminum Compounds↗
PubMed2005

Modulation of gene expression in neonatal rat cardiomyocytes by surface modification of polylactide-co-glycolide substrates.

Myocardial tissue engineering presents a potential treatment option for heart disease. Cardiomyocytes isolated at various stages of development retain the ability to form contractile networks in vitro, which suggests that it should be possible to reconstitute viable myocardium given the appropriate architecture, stimuli, and cardiomyogenic cell source. This study investigates the effects of modifying substrate surface energy (by plasma etching) and protein coating (by fibronectin adsorption) on neonatal rat ventricular myocyte (NRVM) function. Primary NRVMs were cultured for 96 h on modified and control films of a common degradable polymer, polylactide-co-glycolide. Cultures were analyzed for cell spreading, protein content, and mRNA expression of atrial natriuretic factor and beta-myosin heavy chain. The results demonstrate that NRVMs cultured on etched films significantly increased in spreading, myofibril development, protein content, and gene expression of atrial natriuretic factor and beta-myosin heavy chain compared with unetched films, and that this surface energy effect is overwhelmed by the addition of fibronectin. Conclusions from this study are that surface energy and protein adsorption influence the gene expression of adherent NRVMs, and may be important for modulating the function of engineered myocardium.

Animals↗