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PubMed1987

Direct electron transfer reactions of cytochrome c553 from Desulfovibrio vulgaris Hildenborough at indium oxide electrodes.

The direct, heterogeneous, electron transfer reactions of cytochrome c553 from Desulfovibrio vulgaris Hildenborough have been studied at indium oxide optically transparent electrodes. These reactions have been studied using cyclic voltammetry and derivative cyclic voltabsorptometry and the kinetics of heterogeneous electron transfer is quasi-reversible. The thermodynamics and kinetics of electron transfer by this molecule can be studied at this electrode surface without the need for surface modification or the addition of surface promoters or mediators.

Cytochrome c Group↗

PubMed2001

Biodegradable polymeric nanoparticles as drug delivery devices.

This review presents the most outstanding contributions in the field of biodegradable polymeric nanoparticles used as drug delivery systems. Methods of preparation, drug loading and drug release are covered. The most important findings on surface modification methods as well as surface characterization are covered from 1990 through mid-2000.

Adsorption↗

PubMed2005

Controlling nonspecific protein adsorption in a plug-based microfluidic system by controlling interfacial chemistry using fluorous-phase surfactants.

Control of surface chemistry and protein adsorption is important for using microfluidic devices for biochemical analysis and high-throughput screening assays. This paper describes the control of protein adsorption at the liquid-liquid interface in a plug-based microfluidic system. The microfluidic system uses multiphase flows of immiscible fluorous and aqueous fluids to form plugs, which are aqueous droplets that are completely surrounded by fluorocarbon oil and do not come into direct contact with the hydrophobic surface of the microchannel. Protein adsorption at the aqueous-fluorous interface was controlled by using surfactants that were soluble in fluorocarbon oil but insoluble in aqueous solutions. Three perfluorinated alkane surfactants capped with different functional groups were used: a carboxylic acid, an alcohol, and a triethylene glycol group that was synthesized from commercially available materials. Using complementary methods of analysis, adsorption was characterized for several proteins (bovine serum albumin (BSA) and fibrinogen), including enzymes (ribonuclease A (RNase A) and alkaline phosphatase). These complementary methods involved characterizing adsorption in microliter-sized droplets by drop tensiometry and in nanoliter plugs by fluorescence microscopy and kinetic measurements of enzyme catalysis. The oligoethylene glycol-capped surfactant prevented protein adsorption in all cases. Adsorption of proteins to the carboxylic acid-capped surfactant in nanoliter plugs could be described by using the Langmuir model and tensiometry results for microliter drops. The microfluidic system was fabricated using rapid prototyping in poly(dimethylsiloxane) (PDMS). Black PDMS microfluidic devices, fabricated by curing a suspension of charcoal in PDMS, were used to measure the changes in fluorescence intensity more sensitively. This system will be useful for microfluidic bioassays, enzymatic kinetics, and protein crystallization, because it does not require surface modification during fabrication to control surface chemistry and protein adsorption.

Adsorption↗

PubMed2001

Use of solid corrugated particles to enhance powder aerosol performance.

PURPOSE: To study the dispersion performance of non-porous corrugated particles, with a focus on the effect of particle surface morphology on aerosolization of bovine serum albumin (BSA) powders. METHODS: The solid-state characteristics of the spray-dried BSA powders, one consisting of smooth spherical particles and another corrugated particles, were characterized by laser diffraction, X-ray powder diffraction, scanning electron microscopy, confocal microscopy, thermogravimetric analysis, surface area analyzer, and buoyancy method. The powders were dispersed using the Rotahaler and the Dinkihaler coupled to a four-stage liquid impinger operating at 30 to 120 L/min. Fine particle fraction (FPF) was expressed as the wt. % of BSA particles of size < or =5 microm collected from the liquid impinger. RESULTS: Apart from the morphology and morphology-related properties (specific surface area, envelope density), the corrugated particles and spherical particles of BSA had very similar solid-state characteristics (particle size distribution, water content, true density, amorphous nature). Using the Dinkihaler, the FPFs of the corrugated particles were 10-20 wt. % higher than those of the smooth particles. Similar FPF differences were found for the powders dispersed by the Rotahaler, but the relative changes were larger. In addition, the differences were inversely proportional to the air flows (17.3% at 30 L/min, 25.2% at 60 L/min, 13.8% at 90, 8.5% at 120 L/min). Depending on the inhaler, capsule and device retention and impaction loss at the impinger throat were lower for the corrugated particles. CONCLUSIONS: Enhanced aerosol performance of powders can be obtained by surface modification of the particles. The surface asperities of the corrugated particles could lower the true area of contact between the particles, and thus reduce the powder cohesiveness. A distinct advantage of using corrugated particles is that the inhaler choice and air flow become less critical for these particles.

Administration, Inhalation↗

PubMed1964

OOCYTE DIFFERENTIATION AND VITELLOGENESIS IN THE ROACH PERIPLANETA AMERICANA.

The ovary of the roach Periplaneta americana has been studied by techniques of light and electron microscopy. Each ovariole (panoistic type) contains a linear array of oocytes in varying stages of development. Newly formed oocytes become encased by a layer of follicle cells and begin pinocytosis. All subsequent growth stages of the oocytes are dependent, in part, on this phenomenon. All of the pinocytotic caveolae show an unique surface modification; i.e., on their internal surface they have an amorphous or filamentous substance and their external surface is studded with many fine radially oriented spike-like projections. The pinosomes of early oocytes do not contain a demonstrable internal structure; they are thought to contain nutritive substances for the developing oocytes rather than yolk precursors. When the oocyte enters its last stage of growth, characterized by yolk deposition, the caveolae become filled with a dense material which is thought to be the precursors of yolk. Hence the conclusion is drawn that yolk formation is independent of any cytoplasmic organelle system of the oocyte and that the precursors of this deutoplasmic substance are manufactured outside the ovary and are internalized by the process of pinocytosis. Under the phase-contrast microscope the nucleoli of early oocytes are large irregular masses and show the phenomenon of nucleolar emission (fragmentation). These "emissions" become randomly dispersed in the nucleoplasm and some of them come to be intimately associated with the fenestrated nuclear envelope. After this process ceases, the main nucleolar mass becomes vacuolated. Electron micrographs suggest that the constituent particles of the nucleolar emissions migrate from the nucleus through patent pores of the nuclear envelope.

Animals↗

PubMed2005

Surface analysis methods of biomaterials used in oral surgery: literature review.

Titanium is the most frequently used biomaterial in oral surgery because of its positive physical and chemical properties. Clinical studies proved that the properties of titanium can be improved by surface modification techniques. To study the surface of biomaterials, the positive effects of the coatings, the response of the organism (corrosion resistance, physical and chemical stability, the thickness of various coatings, biocompatibility), one must choose and use the adequate analytical method for one's goal. In this article, the authors present the most frequently used analytical methods for the study of the surface morphology and composition of biomaterials. Also, they outline the advantages and disadvantages of specific analytical methods and the field where they are used.

Biocompatible Materials↗

PubMed2004

Poly(ethylene oxide) surfactant polymers.

We report on a series of structurally well-defined surfactant polymers that undergo surface-induced self-assembly on hydrophobic biomaterial surfaces. The surfactant polymers consist of a poly(vinyl amine) backbone with poly(ethylene oxide) and hexanal pendant groups. The poly(vinyl amine) (PVAm) was synthesized by hydrolysis of poly(N-vinyl formamide) following free radical polymerization of N-vinyl formamide. Hexanal and aldehyde-terminated poly(ethylene oxide) (PEO) were simultaneously attached to PVAm via reductive amination. Surfactant polymers with different PEO:hexanal ratios and hydrophilic/hydrophobic balances were prepared, and characterized by FT-IR, 1H-NMR and XPS spectroscopies. Surface active properties at the air/water interface were determined by surface tension measurements. Surface activity at a solid surface/water interface was demonstrated by atomic force microscopy, showing epitaxially molecular alignment for surfactant polymers adsorbed on highly oriented pyrolytic graphite. The surfactant polymers described in this report can be adapted for simple non-covalent surface modification of biomaterials and hydrophobic surfaces to provide highly hydrated interfaces.

Aldehydes↗

PubMed2006

Effect of acetic NaF solution on the corrosion behavior of stainless steel orthodontic brackets.

This study assessed the effect of acetic NaF solutions on stainless steel orthodontic brackets. Acetic acid was added to a 0.1% NaF solution to make two solutions, one with pH 3.5 and the other with pH 6. For the two different stainless steel brackets (Tomy, Dentaurum) used in this study, they had a similar elemental composition--except with Mo (molybdenum) in the Tomy bracket. The brackets were then immersed in the prepared test solutions for three days and their responses evaluated. In terms of hydrofluoric acid (HF) concentration, the 0.1%/pH 3.5 solution showed a high HF concentration at 227 ppm, while that of 0.1%/pH 6 solution was very low at 7 ppm. In terms of color change and element release, only the Dentaurum brackets in 0.1%/pH 3.5 solution showed an appreciable color change (deltaE* = 4.0) and released a great amount of elements (Fe, Cr, Ni, Mn) after three days. Otherwise, regardless of pH value and product, only minor color change (deltaE* < 1.0) and negligible element release occurred. In terms of surface modification, no visible changes in surface morphology were observed in any product after immersion in test solutions.

Acetic Acid↗

PubMedDate not supplied

Factors affecting light transmission of single-use, plastic light-curing tips.

Recently, manufacturers introduced presterilized, single-use, plastic light-curing tips to be used either routinely or on patients with known or questionable communicable health concerns. The purpose of this study was to examine the effect of these single-use tips on light transmission compared to conventional fiber-optic bundles in a variety of commercial light-curing units. Also, the effects of surface contact with the plastic tips (human tissues, reflective or opaque media, and barrier films) were evaluated. Where applicable, single-use tips from two sources (Caulk/Dentsply and Demetron) were placed in commercial curing units (Optilux 150 and 500, MAX 100, Spectrum Curing Light, and 3M XL-3000), and the intensity was compared to that of the conventional glass curing tip used with that specific curing unit. Intensity readings were also made for 6 continuous minutes using plastic tips in a high-intensity curing unit to simulate veneer bonding. If the sides of the plastic tip came in contact with the operator's fingers or the patient's tongue and/or cheek during a clinical procedure, a lowering of transmitted light intensity resulted. The glow emitted from the sides of the tip when in use may be annoying to the operator. To prevent this glare, the operator may be tempted to treat the sides of the tip by painting, applying a thin polymer barrier, abrasion, or wrapping in an opaque reflective material (aluminum foil). A significant decrease in light intensity can result if plastic curing tips contact oral tissues or bare hands. Application of thin polymer barriers was found to significantly reduce light transmission value. Also, surface modification (coating with paint or surface scratches) was found to greatly reduce light intensity levels, while wrapping the tip in aluminum foil produced a very small increase. Results indicated that transmitted light intensity with use of plastic tips was dependent upon both the brand of plastic tip tested and the different photocuring units. Either a slight increase or a slight decrease in intensity was noted. Plastic tips did not degrade in transmitted intensity when exposed to the heat produced during a simulated veneering scenario. In summary, use of plastic, single-use light-curing tips can provide adequate intensity for photoactivated restorative techniques; however, the clinician must be aware of specific, clinically relevant limitations with their use. Clinicians must also note that these tips are not designed for re-use.

Analysis of Variance↗

PubMed2006

Biomaterials surface characterization and modification.

This paper presents several examples of recent work in the field of surface modification and characterization of biomaterials. Due to the explosion of techniques and approaches in this area, a complete review would be unmanageable in a single paper. Rather selected examples taken from such different areas as bone-contacting devices, drug eluting stents, and immobilization of novel biomolecules are presented. The aim is to place the existing and quickly developing background of analytical and synthetic biomaterial surface science into the current perspective of this rapidly evolving discipline.

Artificial Organs↗

PubMed2006

Enhancing surface free energy and hydrophilicity through chemical modification of microstructured titanium implant surfaces.

Roughness-induced hydrophobicity, well-known from natural plant surfaces and intensively studied toward superhydrophobic surfaces, has currently been identified on microstructured titanium implant surfaces. Studies indicate that microstructuring by sandblasting and acid etching (SLA) enhances the osteogenic properties of titanium. The undesired initial hydrophobicity, however, presumably decelerates primary interactions with the aqueous biosystem. To improve the initial wettability and to retain SLA microstructure, a novel surface modification was tested. This modification differs from SLA by its preparation after acid etching, which was done under protective gas conditions following liquid instead of dry storage. We hypothesized that this modification should have increased wettability due to the prevention of contaminations that occurs during air contact. The main outcome of dynamic wettability measurements was that the novel modification shows increased surface free energy (SFE) and increased hydrophilicity with initial water contact angles of 0 degrees compared to 139.9 degrees for SLA. This hydrophilization was kept even after any drying. Reduced hydrocarbon contaminations were identified to play a possible role in altered surface thermodynamics. Such surfaces aim to retain the hydrophilicity and natural high surface energy of the Ti dioxide surface until surgical implants' insertion and are compared in this in vitro study with structural surface variants of titanium to compare roughness and chemically induced wettability.

Acids↗

PubMed1978

Modifications of lectin binding on human leukemic cells after neuraminidase treatment.

Cell surface modifications after vibrio cholerae neuraminidase treatment were investigated using three different tritiated lectins: Concanavalin A, Ricinus sanguineus agglutinin (R.S.A.) and Robinia pseudoacacia lectin. Lectin binding measurements were performed on untreated and enzyme treated cells. The cells used were from chronic and acute leukemic donors. After neuraminidase treatment, a significant increase in the number of receptor sites, from 1 to 3 times, was found in all cases tested and for all three lectins utilized with only one exception. The affinity constant was generally decreased after neuraminidase treatment. The increase in number lectin binding sites, indicating extensive modification of the cell surface, is completely consistant with the known importance of sialic acid in determining immunogenicity.

Binding Sites↗

PubMed2002

Altering the surface properties of baculovirus Autographa californica NPV by insertional mutagenesis of the envelope protein gp64.

The envelope protein gp64 of the baculovirus Autographa californica nuclear polyhedrosis virus is essential for viral entry into insect cells, as the glycoprotein both mediates pH-dependent membrane fusion and binds to host cell receptors. Surface modification of baculovirus particles by genetic engineering of gp64 has been demonstrated by various strategies and thus has become an important and powerful tool in molecular biology. To improve further the presentation of peptides on the surface of baculovirus particles, several insertion sites within the gp64 envelope protein were selected by their theoretical maximum surface probability and investigated for efficient peptide presentation. The ELDKWA peptide of the gp41 of HIV-1, specific for the human mAb 2F5, was inserted into 17 different positions of the glycoprotein gp64. Propagation of viruses was successful in 13 cases, mutagenesis at four positions did not result in production of intact virus particles. Western blotting, FACS analysis and ELISA were used for characterization of the different binding properties of the mutants. Insertion of this peptide into the native envelope protein resulted in high avidity display on the surface of baculovirus particles. This approach offers the possibility of effective modification of surface properties in regard to host range specificity and antigen display.

Amino Acid Sequence↗

PubMed2006

Surface confined ionic liquid as a stationary phase for HPLC.

Trimethoxysilane "ionosilane" derivatives of room temperature ionic liquids based on alkylimidazolium bromides were synthesized for attachment to silica support material. The derivatives 1-methyl-3-(trimethoxysilylpropyl)imidazolium bromide and 1-butyl-3-(trimethoxysilylpropyl)imidazolium bromide were used to modify the surface of 3 microm diameter silica particles to act as the stationary phase for HPLC. The modified particles were characterized by thermogravimetric analysis (TGA) and (13)C and (29)Si NMR spectroscopies. The surface modification procedure rendered particles with a surface coverage of 0.84 micromol m(-2) for the alkylimidazolium bromide. The ionic liquid moiety was predominantly attached to the silica surface through two siloxane bonds of the ionosilane derivative (63%). Columns packed with the modified silica material were tested under HPLC conditions. Preliminary evaluation of the stationary phase for HPLC was performed using aromatic carboxylic acids as model compounds. The separation mechanism appears to involve multiple interactions including ion exchange, hydrophobic interaction, and other electrostatic interactions.

Journal Article↗

PubMed2006

Nonradiative surface plasmon assisted microscale Marangoni forces.

When a liquid droplet experiences a temperature inhomogeneity along its bounding surface, a surface energy gradient is engendered, which when, in a continuous sense, exceeding a threshold, results in a convective flow dissipating the energy. If the associated temperature gradients are sustained by the interface between the liquid and a supporting substrate, the induced flow can result in the lateral motion of the droplet overcoming the viscosity and inertia. Recently, pico-liter adsorbed and applied droplets were shown experimentally to be transported, and divided by the decay of optically excited surface plasmons into phonons in a thin gold foil. The decaying events locally modify the temperature of the liquid-solid interface, establishing microscale thermal gradients of sufficient magnitude for the droplet to undergo thermocapillary flow. We present experimental evidence of such gradients resulting in local surface modification associated with the excitation of surface plasmons. We show theoretically that the observed effect is due to Marangoni forces, and computationally visualize the flow characteristics for the experimental parameters. As an application based on our results, we propose a method for an all-optical modulation of light by light mediated by the droplet oscillations. Furthermore, the results have important consequences for microfluidics, droplet actuation, and simultaneous surface plasmon resonance sensing and spectroscopy.

Journal Article↗

PubMed2005

Efficient probe immobilization on poly (dimethylsiloxane) for sensitive detection of proteins.

Chemical surface modification methods were investigated to activate surface of poly-(dimethylsiloxane) (PDMS) for probe immobilization in enzyme-linked immunosorbent assay (ELISA). The investigations started from dramatization of PDMS surface with (3-aminopropyl)-triethoxysilane (APTES). Amino groups generated by APTES were either derived into carboxyl group by Succinic acid anhydride (SAA), then captured the protein through the heterobifunctional cross-linker, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC), or directly reacted with homobifunctional cross-linker, glutaraldehyde (GA). Rabbit IgG, Goat IgG, Human IgA and Rat IgG were covalently immobilized on PDMS by both methods, and examined through well-organized competitive inhibition ELISA. The results demonstrated that both GA and EDC based methods had good covalent immobilization capability, and the EDC method had higher efficiency than the GA method. The competitive ELISA with probe immobilization through EDC had a detection limit of pg/ml level. The method was proved to be applicable for immobilization of different proteins. The topography of the immobilized protein properties was studied by atomic force microscope (AFM), demonstrating that the immobilization by GA had protein conglomeration, resulting in poorer uniformity and lower immobilization efficiency than EDC method. The possible reason is protein inter-molecule crossing linkage by the homobifunctional group of GA. Due to its simplicity, low cost, and high immobilization efficiency, EDC based immobilization method could provide great potential for making ELISA protein chips based on PDMS.

Animals↗

PubMedDate not supplied

Development of the biologically active Guglielmi detachable coil for the treatment of cerebral aneurysms. Part II: an experimental study in a swine aneurysm model.

BACKGROUND AND PURPOSE: Ion implantation is a surface-modification technology that creates a borderless surface on protein-coated platinum; this change in physical and chemical properties on the surface of Guglielmi detachable coils (GDCs) appears to enhance cell proliferation and adhesion. Our purpose was to evaluate the effect of ion implantation on GDCs in an experimental aneurysm model. METHODS: GDCs were coated with either type I collagen, fibronectin, vitronectin, laminin, or fibrinogen. Using He+ or Ne+ 1 x 10(14-15) ions/cm2, ion implantation was performed on these protein-coated GDCs (GDC-Is). A total of 56 experimental aneurysms were constructed microsurgically in the common carotid arteries of 28 swine. These experimental aneurysms were embolized with standard GDCs (n = 23), collagen GDC-Is (n = 11), vitronectin GDC-Is (n = 6), laminin GDC-Is (n = 4), fibrinogen GDC-Is (n = 6), and fibronectin GDC-Is (n = 6). The animals were sacrificed at day 14 after coil embolization. The physical properties of the new coils (friction on delivery, deployment into aneurysms, trackability, etc) and the development of tissue scarring and neoendothelium across the aneurysm's orifice were evaluated macroscopically and microscopically. RESULTS: No evidence of increased coil friction/stiffness was observed during delivery of GDC-Is through microcatheters in this aneurysm model. A more intense scar formation and neoendothelium at the neck of aneurysms were observed macroscopically when treated with GDC-Is. Significant differences in the proportion of neck coverage between standard GDCs (48.3% +/- 20.5%) and all GDC-I groups were observed (collagen GDC-I-89.4% +/- 14.9%, P < .01; vitronectin GDC-I-71.5% +/- 7.0%, P < .05; laminin GDC-I-76.5% +/- 11.0%, P < .05; fibrinogen GDC-I-74.8% +/- 13.9%, P < .05; fibronectin GDC-I-87.5% +/- 15.0%, P < .01). Light microscopy showed a well-organized fibrous tissue bridging the aneurysm's neck when using GDC-Is, whereas only a fibrin-like thin layer covered the standard GDC surfaces. CONCLUSION: GDC-Is indicated a more intense inflammatory response in the aneurysm body and dome and faster re-endothelial coverage of the neck of the aneurysm. This accelerated histologic response may decrease the chances of coil compaction and aneurysm recanalization. This technology may improve anatomic and clinical outcomes in patients harboring intracranial aneurysms.

Animals↗

PubMed2000

Exposure of rainbow trout (Oncorhynchus mykiss) to nonylphenol is associated with an increased chloride cell fractional surface area.

Nonylphenol is a biodegradation product of a widely used group of non-ionic detergents. Because of its ubiquitous distribution and persistence, nonylphenol is present in surface waters as a pollutant. Little is known about its biological effects at environmentally relevant concentrations other than its action as a xenoestrogen. The goal of the present paper was to study the trout gill surface epithelium as the major interface between fish and water in view of possible morphological alterations due to exposure to nonylphenol. Rainbow trout were intermittently exposed to 10 micrograms/l nonylphenol and gill samples from experimental and control animals were investigated by scanning electron microscopy. Gill surface epithelium was scrutinised for changes in chloride cell density and their status regarding cell surface modifications. In addition, chloride cell fractional surface area (CCFA) was determined by morphometrical methods. Statistical analysis revealed a highly significant increase of CCFA in animals exposed to nonylphenol as compared to control animals (P = 0.0001). Semi-quantitative assessment of the other parameters suggested a higher chloride cell density and a larger proportion of chloride cells bearing microvilli. Taken together, these results provide evidence that exposure of trout to nonylphenol is associated with a substantial increase in the active interface of chloride cells with water. We interpret these findings as being a means to further the fish's capacity for calcium exchange.

Animals↗