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At least 883 records · Page 49Linked to original sources

PubMed1996

Biocompatibility in transfusion medicine.

The first measurable event upon interaction of artificial surfaces with blood is adsorption of proteins within seconds or minutes. At a later stage, blood cells interact with the surfaces through the initially deposited protein layer. The chemical composition of the surface is only one criterion for differential deposition of various plasma proteins, with molecular motion (polymer chain ends, loops and their flexibility), and topography (roughness, porosity) of the surface decisively influencing the interactions as well. Initially incompatible surfaces, which may be dangerous to the patient, may be rendered compatible by physicochemical surface modifications. Modern methods to estimate biocompatibility have become so sensitive that they may detect biological modifications of the blood after contact with a surface, which has no consequence for the patient. In these cases it is often difficult to decide whether a material should be classified as biocompatible or non-biocompatible. This paper discusses some methods that we have used for the study of biocompatibility of extracorporeal circuitry. It seems to us that minute signs of laboratory evidence for bioincompatibility should not preclude usage of the material in a clinical setting.

Biocompatible Materials↗

PubMed1999

A human histologic analysis of osseotite and machined surfaces using implants with 2 opposing surfaces.

A human histologic study was conducted to compare the percentage of bone-to-implant contact (BIC) at 6 months for Osseotite and machined, commercially pure titanium implant surfaces. To eliminate potential influences caused by differences in bone density at different intraoral locations, 2 mm x 5 mm, threaded, 2-surfaced titanium implants were manufactured; 1 side received the Osseotite surface modification and the opposite side maintained a machined surface. In each of 11 patients, 1 test implant was placed in the posterior maxilla (Types III and IV bone) during conventional dental implant surgery. Following 6 months of unloaded healing, the conventional implants were uncovered, and the test implants and surrounding hard tissue were removed. Histologic analysis indicated that at 6 months of unloaded healing, the mean BIC value for the Osseotite surfaces (72.96% +/- 25.13%) was statistically significantly higher (P < 0.05) than the mean BIC value for the machined surfaces (33.98% +/- 31.04%). When the BIC values for the machined and Osseotite surface pairs were ranked from high to low based on the machined BIC value range of 93% to 0%, the upper 50th percentile (20 surface pairs) mean BIC value was 86.1% +/- 16.7% for the Osseotite surfaces and 60.1% +/- 18.3% for the machined surfaces. The lower 50th percentile (19 surface pairs) mean BIC value was 59.1% +/- 25.3% for the Osseotite surfaces and 6.5% +/- 10.8% for the machined surfaces. Differences between mean BIC values for the 2 surfaces in both the upper and lower 50th percentiles were statistically significant (P < 0.05). The results of this study indicate that in the poorer quality bone typically found in the posterior maxilla, a statistically significantly higher percentage of bone contacts Osseotite surfaces when compared to opposing machined surfaces on the same implant.

Alveolar Process↗

PubMed2005

Cathodic modifications of platinum surfaces in organic solvent: reversibility and cation type effects.

Cathodic modification of platinum surfaces leads to the formation of iono-platinic phases ([Pt(n-), M+, MX]), which involves the insertion of cations and salts into the platinum electrode. This process was investigated at the local scale by in situ observation of surface electrochemical processes by atomic force microscopy (EC-AFM) techniques as a function of the salt and the injected charge, with special attention about the process reversibility. AFM images recorded in solution after the cathodic modifications of well-defined platinum surfaces [epitaxial platinum deposit on (100) MgO substrate] show drastic modification on the morphology of the surface, confirming previous ex situ studies. The amplitude of the modifications directly depends on both the nature of supporting electrolyte and the quantity of charge injected into the platinum. As long as the injected charge remains small enough to maintain the adhesion of the Pt deposit onto the MgO substrate, the process was found to be fully reversible. Indeed, impressive morphology changes occur under the cathodic treatment (formation of [Pt(n-), M+, MX]) but the initial geometry is totally recovered after reoxidation of the iono-platinic phase. This cycle of reduction-reoxidation can be performed several times without any significant alteration of the recovered surface and of its structural characteristics. It is suggested that the modification starts at the interface solution platinum surface and then its insertion into the platinum surface.

Journal Article↗

PubMed1998

[Comparison of changes in oncogene of human embryo lung cells before and after chemical modification for chrysotile].

OBJECTIVE: To seek for a suitable chamical agent for surface modification of chrysotile. METHODS: The effects of aluminum citrate, mixed rare earth and sodium selenite on c-Ha-ras oncogene and P21ras protein in the transformation of human embryo lung cells caused by chrysotile were studied. RESULTS: The transcription level of c-Ha-ras oncogene and the content of P21ras in those exposed to chrysotile were significantly higher than those in the controls. The transcription level of c-Ha-ras oncogene and the content of P21ras in those exposed to chrysotile treated in advance with three kinds of chemicals mentioned above were significantly lower than those in untreated. CONCLUSION: Treatment of chrysotile with three kinds of above-mentioned chemicals in advance could reduce its carcinogenecity in human beings.

Aluminum Compounds↗

PubMed2001

In vitro biocompatibility of resorbable experimental glass ceramics for bone substitutes.

Tricalcium phosphate ceramics (TCPs) are increasingly used as bone substitutes. They demonstrate good biocompatibility and degrade relatively slowly. New glass ceramics based on calcium alkali orthophosphates (Ca(2)KNa(PO(4))(2)) were developed that degrade faster than TCP but could have reduced biocompatibility due to their high solubility. Therefore, they were modified by a neutralizing surface treatment. The aim of this study was to evaluate the biocompatibility of some of these ceramics, GB1a, GB9, and GB14, which differ in the amount of added Na, K, Mg, or Si ions, with standard and modified surfaces. The in vitro cytotoxicity of the ceramics GB1a, GB9, and GB14 was determined by the agar diffusion and filter test and the microculture tetrazolium (MTT) assay. In order to investigate the influence of surface modification, these three ceramics were compared to their surface-treated counterparts, GB1aN, GB9N, and GB14N. GB1a, the ceramic with the highest in vitro solubility, showed the strongest toxic influence in all cell culture tests. GB9 and GB14 produced better results. In contrast, the counterparts with modified surfaces exhibited no (GB9N, GB14N) or weak (GB1aN) signs of cytotoxicity. It is concluded that the toxicity of the ceramics GB1a, GB9, and GB14 depends on their solubility. A positive influence of the surface treatment on in vitro biocompatibility was demonstrated. Therefore, the surface-treated glass ceramics could be promising materials for bone replacement.

3T3 Cells↗

PubMed2001

Removal of interfering elements in ICP-QMS for the determination of Pt, Rh, and Pd by chemically modified sample introduction capillaries.

New on-line methods developed for the determination of Pt, Rh, and Pd by inductively coupled plasma-quadrupole mass spectrometry (ICP-QMS) include separation of elements which might lead to spectral interference in the quadrupole instrument. The fused-silica capillaries generally used for transport of the sample to mu-flow nebulizers have been chemically modified with ion-exchanger compounds to remove interfering elements such as Cu, Pb, or Hf. Characterization of the modification procedures by atomic-force microscopy showed that the quality of the quartz material and the kind of modification had a decisive influence on the yield of surface modification, and thus the exchange capacity of the capillaries.

Journal Article↗

PubMed2005

Point mutation detection with the sandwich method employing hydrogel nanospheres by the surface plasmon resonance imaging technique.

We propose a surface modification procedure to construct DNA arrays for use in surface plasmon resonance (SPR) imaging studies for the highly sensitive detection of a K-ras point mutation, enhanced with hydrogel nanospheres. A homobifunctional alkane dithiol was adsorbed on Au film to obtain the thiol surface, and ethyleneglycol diglycidylether (EGDE) was reacted to insert the ethyleneglycol moiety, which can suppress nonspecific adsorption during SPR analysis. Then streptavidin (SA) was immobilized on EGDE using tosyl chloride activation. Biotinylated DNA ligands were bound to the SA surface via biotin-SA interaction to fabricate DNA arrays. In SPR analysis, the DNA analyte was exposed on the DNA array and hybridized with the immobilized DNA probes. Subsequently, the hydrogel nanospheres conjugated with DNA probes were bound to the DNA analytes in a sandwich configuration. The DNA-carrying nanospheres led to SPR signal enhancement and enabled us to discriminate a K-ras point mutation in the SPR difference image. The application of DNA-carrying hydrogel nanospheres for SPR imaging assays was a promising technique for high throughput and precise detection of point mutations.

Base Sequence↗

PubMed1980

Fluid transport in a thick layer above an active ciliated surface.

The discrete cilia approach is employed to describe the flow field above an active ciliated surface in a layer of finite depth. The infinite-size cilia surface model predicts a uniform flow above the cilia surface. Modifications as a result of a finitely extending cilia surface inside a finite-size dish predict a backward parabolic profile above an active cilia surface. Experiments are described which demonstrate a good fit between theoretical predictions and observations. The results provide a sound physical basis for the proper interpretation of fluid-flow observations close to an active ciliary field.

Animals↗

PubMed2002

On the importance of ions and ion-molecule reactions to plasma-surface interface reactions.

Ions are known to be key players in many plasma processes, including anisotropic etching, film deposition and surface modification. The relationship between plasma ions, film properties, and surface interactions of other plasma species is not, however, well known. Using our Imaging of Radicals Interacting with Surfaces (IRIS) technique, along with plasma ion mass spectrometry (PI-MS), and surface analysis data, we have measured the effects of ion bombardment on the surface interactions of SiF2 in SiF4 plasmas and of CF2 in C3F8 and C4F8 plasmas. SiF2 is a known product of F-atom etching of Si, and CF2 has also been cited as a product of fluorocarbon etching of Si. With both molecules, we measure surface generation when the surface is bombarded by all the plasma species. Removal of ions from the plasma molecular beam results in a net decrease in surface generation for both molecules at all powers. Results in both systems are compared with the gas-phase ion-molecule reaction data of Armentrout and coworkers. Preliminary guided-ion beam mass spectrometry results taken in the Armentrout laboratories for the Ar+ + C3F8 reaction system are also presented.

Journal Article↗

PubMed2001

Triggered intracellular activation of disulfide crosslinked polyelectrolyte gene delivery complexes with extended systemic circulation in vivo.

We have developed polyelectrolyte gene delivery vectors that display good extracellular stability and are activated intracellularly to permit transgene expression. The strategy comprises covalent crosslinking of primary amines in poly-L-lysine/DNA complexes with a crosslinking agent that can later be cleaved by reduction. Crosslinked complexes maintained the same size and surface charge but showed increased stability against polyelectrolyte exchange with poly-L-aspartic acid. Surface modification with polyethyleneglycol improved solubility and masked their positive surface charge. Crosslinked complexes showed 10-fold increased plasma circulation following intravenous administration to Balb/c mice. In the absence of chloroquine, the levels of transgene expression in B16F10 murine melanoma cells were similar for crosslinked and non-crosslinked complexes, however, chloroquine selectively potentiated transgene expression by the non-crosslinked complexes. Cellular uptake of the complexes was the same, irrespective of crosslinking. Following microinjection into the cytoplasm of Xenopus oocytes, or the cytoplasm or nucleus of Rat-1 fibroblasts, crosslinked complexes mediated the same transgene expression as non-crosslinked complexes, indicating crosslinked complexes are rapidly reduced and activated intracellularly. We therefore hypothesize that the lower in vitro transfection activity of crosslinked complexes in the presence of chloroquine is due to reduced transfer from endosome to cytoplasm, mainly due to increased stability against destabilization by chloroquine. The extended systemic circulation together with triggered intracellular activation makes these complexes a promising system for targeted gene delivery in vivo.

Animals↗

PubMedDate not supplied

Novel drug delivery system by surface modified magnetic nanoparticles.

In the recent progress of gene and cell therapy, novel drug delivery system (DDS) has been required for efficient delivery of small molecules/drugs and also the safety for clinical usage. We have already developed the unique transfection technique by preparing magnetic vector and using permanent magnet. This technique can improve the transfection efficiency. In this study, we directly associated plasmid DNA with magnetic nanoparticles, which can potentially enhance their transfection efficiency by magnetic force. Magnetic nanoparticle, such as magnetite, its average size of 18.7 nm, can be navigated by magnetic force and is basically consisted with oxidized Fe that is commonly used as the supplement drug for anemia. The magnetite particles coated with protamine sulfate, which gives a cationic surface charge onto the magnetite particle, significantly enhanced the transfection efficiency in vitro cell culture system. The magnetite particles coated with protamine sulfate also easily associated with cell surface, leading to high magnetic seeding percentage. From these results, it was found that the size and surface chemistry of magnetic particles would be tailored to meet specific demands on physical and biological characteristics accordingly. Overall, magnetic nanoparticles with different surface modification enhance the association with plasmid DNA and cell surface as well as HVJ-E, which potentially help to improve the drug delivery system.

Animals↗

PubMed1994

Sterically stabilized liposomes: physical and biological properties.

Advanced liposomal therapeutics has been attained by liposome surface modification, initially with specific glycolipids and subsequently with surface-grafted PEG, reducing in vivo rapid recognition and uptake, giving prolonged blood circulation, and providing selective localization in tumors and other pathological sites, as described in recent reviews. The result is improved efficacy of encapsulated agents. The surface PEG may produce a steric barrier, as described for colloids. Reduced in vivo uptake may result from inhibition of plasma-protein adsorption, or opsonization, by the steric coating. Several physical studies support this mechanism, including electrophoretic mobility (zeta potential). Our previous results for 2000-dalton PEG indicated a coating thickness about 5 nm, in agreement with independent measurements. We report here results for 750 to 5000-dalton PEGs. The calculated coating thickness increases with molecular weight in a nonlinear fashion. The dependence of blood circulation and tissue distribution on PEG molecular weight correlates with zeta-potential estimates of PEG-coating thickness. Effects on tissue distribution are reported for liver and spleen, the major phagocytic organs. The biological properties of these liposomes depend on the surface polymer rather than the lipid bilayer, yielding important advantages for lipid-mediated control of drug interaction and release without affecting the biodistribution.

Animals↗

PubMedDate not supplied

Surface energy of etched ceramic.

PURPOSE: In a previous article the authors examined the evolution of the bond strengths of 2 dental feldspathic ceramics. The objective of the present study was to evaluate the effect of surface modifications with hydrofluoric acid gel (concentration 10%) on the surface energy of 2 dental feldspathic ceramics (GC and PVS). MATERIALS AND METHODS: For an energy characterization, 30 samples of GC and 30 samples of PVS were built. This study comprised the measurement of contact angles to determine the work of adhesion (WA) of the 2 ceramics. The evolution of the work of adhesion depended on the action of the hydrofluoric acid gel on the roughness of the surface of the 2 ceramics. RESULTS: In a polished state PVS presented a higher work of adhesion than GC. Etching the ceramics with hydrofluoric acid gel increased the work of adhesion, especially for GC, but this treatment was not sufficient to obtain a high work of adhesion. CONCLUSION: Etching with hydrofluoric acid gel was not sufficient to raise the work of adhesion of the 2 ceramics. Silanization is preferable to etching.

Acid Etching, Dental↗

PubMedDate not supplied

Anodization: a promising nano-modification technique of titanium implants for orthopedic applications.

Anodization is a well-established surface modification technique that produces protective oxide layers on valve metals such as titanium. Many studies have used anodization to produce micro-porous titanium oxide films on implant surfaces for orthopedic applications. An additional hydrothermal treatment has also been used in conjunction with anodization to deposit hydroxyapatite on titanium surfaces; this is in contrast to using traditional plasma spray deposition techniques. Recently, the ability to create nanometer surface structures (e.g., nano-tubular) via anodization of titanium implants in fluorine solutions have intrigued investigators to fabricate nano-scale surface features that mimic the natural bone environment. This paper will present an overview of anodization techniques used to produce micro-porous titanium oxide structures and nano-tubular oxide structures, subsequent properties of these anodized titanium surfaces, and ultimately their in vitro as well as in vivo biological responses pertinent for orthopedic applications. Lastly, this review will emphasize why anodized titanium structures that have nanometer surface features enhance bone forming cell functions.

Coated Materials, Biocompatible↗

PubMed2005

Mediating specific cell adhesion to low-adhesive diblock copolymers by instant modification with cyclic RGD peptides.

One promising strategy to control the interactions between biomaterial surfaces and attaching cells involves the covalent grafting of adhesion peptides to polymers on which protein adsorption, which mediates unspecific cell adhesion, is essentially suppressed. This study demonstrates a surface modification concept for the covalent anchoring of RGD peptides to reactive diblock copolymers based on monoamine poly(ethylene glycol)-block-poly(D,L-lactic acid) (H(2)N-PEG-PLA). Films of both the amine-reactive (ST-NH-PEG(2)PLA(20)) and the thiol-reactive derivative (MP-NH-PEG(2)PLA(40)) were modified with cyclic alphavbeta3/alphavbeta5 integrin subtype specific RGD peptides simply by incubation of the films with buffered solutions of the peptides. Human osteoblasts known to express these integrins were used to determine cell-polymer interactions. The adhesion experiments revealed significantly increased cell numbers and cell spreading on the RGD-modified surfaces mediated by RGD-integrin-interactions.

Adhesiveness↗

PubMed2001

A factorial analysis of silanization conditions for the immobilization of oligonucleotides on glass surfaces.

The modification of glass surfaces with (3-mercaptopropyl)trimethoxysilane and the application of this to DNA chip technology are described. A range of factors influencing the silanization method, and hence the number of surface-bound, chemically active thiol groups, were investigated using a design of experiment approach based on analysis of variance. The number of thiol groups introduced on glass substrates were measured directly using a specific radiolabel, [14C]cysteamine hydrochloride. For liquid-phase silanization, the number of surface-bound thiol groups was found to be dependent on both postsilanization thermal curing and silanization time and relatively independent of silane concentration, reaction temperature, and sample pretreatment. Depending on the conditions used in liquid-phase silanization, (1.3-9.0) x 10(12) thiol groups/cm2 on the glass samples were bound. The reliability and repeatability of liquid- and vacuum-phase silanization were also investigated. Eighteen-base oligonucleotide probes were covalently attached to the modified surfaces via a 3'-amino modification on the DNA and subsequent reaction with the cross-linking reagent N-(gamma-maleimidobutyryloxy) succinimide ester (GMBS). The resulting probe levels were determined and found to be stoichiometric with that of the introduced thiol groups. These results demonstrate that silanization of glass surfaces under specific conditions, prior to probe attachment, is of great importance in the development of DNA chips that use the simple concept of the covalent attachment of presynthesized oligonucleotides to silicon oxide surfaces.

Factor Analysis, Statistical↗

PubMed1988

Immobilization of enzymes on polypropylene bead surfaces by anhydrous ammonia gaseous plasma technique.

Anhydrous ammonia gaseous plasma technique was used for the surface modification of polypropylene beads. Amino groups were added onto the surfaces of beads by exposing them to ammonia plasma. Through these amino groups covalent immobilization of glucose oxidase and peroxidase were carried out. The total amounts of immobilized glucose oxidase and immobilized peroxidase were found to be 52 and 43 micrograms/cm2, respectively. To assess the stability of enzyme-polypropylene linkage, beads with covalently immobilized glucose oxidase and peroxidase were washed with phosphate buffer. It was found that after the removal of the adsorbed enzymes, the concentration of covalently immobilized enzymes tended to reach a steady state. After additional washing with buffer for 5 to 6 h, 40-55% of the immobilized enzymes were found to be in the active form.

Ammonia↗

PubMed1995

Synthesis and characterization of fluoropolymeric substrata with immobilized minimal peptide sequences for cell adhesion studies. I.

In this work, poly(tetrafluoroethylene-co-hexafluoropropylene) (also known as fluorinated ethylene propylene; FEP) was functionalized at the surface using a radio frequency glow discharge plasma. This particular surface modification produced controlled densities of hydroxyl functionality on the FEP surface. These surface hydroxyl groups provided sites for the covalent attachment of minimal peptide sequences, that are specific for neuronal attachment. FSCA, ATR-FTIR, ToF-SIMS, and fluorescence spectroscopy were used to evaluate peptide reaction efficiencies and to verify that intact peptide sequences were covalently attached to the FEP surfaces. These modified substrata were then used to study the cell attachment and response to covalently bound minimal peptide sequences. Cell attachment and differentiation results using NG108-15 and PC12 neuronal cell lines are presented in the adjoining paper by Ranieri et al.

Amino Acid Sequence↗