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At least 649 records · Page 36Linked to original sources
PubMed1998

Behavior of CHO cells on phosphated cellulose membranes.

Phosphate groups (negatively charged chemical groups) were grafted onto the surface of cellulose membranes by a reaction between hydroxyl groups of cellulose and phosphorus pentoxide to observe the effect of phosphate groups on cellular behavior. X-ray photoelectron spectroscopy (XPS) was used to determine phosphorylation. Captive bubble contact angle measurement was used to determine surface wettability. XPS was also used to analyze serum protein adsorption. Chinese hamster ovary (CHO) cells were maintained in Ham's F-12 nutrient mixture with and without fetal calf serum. Total cell area and shape factor were analyzed using image-analyzing software. Serum proteins showed higher adsorption on phosphated cellulose. Cell spreading on phosphated membranes was greater than on the cellulose membrane that served as control. The cell growth rate was faster compared to the control. Large cell aggregates were not found on the phosphated membranes, in contrast to the control membrane. The cells on the control were aggregated regardless of the existence of divalent cations in the medium.

Adsorption↗
PubMed1998

Effect of protein and cell behavior on pattern-grafted thermoresponsive polymer.

A thermoresponsive copolymer, poly(Nisopropylacrylamide-co-acrylic acid), was coupled with azidoaniline. The azidophenyl-derivatized copolymer was grafted in a specific pattern on a polystyrene matrix by photolithography. The surface micropattern appeared and disappeared interchangeably, as observed under a phase-contrast microscope, by varying the temperature between 10 degrees C and 37 degrees C. The copolymer-grafted polystyrene surface was hydrophobic at 37 degrees C and hydrophilic at 10 degrees C. Albumin and fibronectin adsorption on the matrix was investigated using the fluorescent-labeling method. Fibronectin adsorbed onto both the grafted and nongrafted regions, while albumin adsorbed more onto the nongrafted regions than the grafted regions. Protein adsorption did not affect surface wettability. Mouse fibroblast STO cells were cultured on tissue culture plates pattern-grafted with the thermoresponsive copolymer. Fibronectin adsorption enhanced cell spreading, while albumin reduced it. When the temperature was lowered, the cells selectively detached from the surface areas grafted with the thermoresponsive copolymer when cultured in serum-free medium; the cells partially detached from these areas when cultured in serum-containing medium. The effect of serum proteins on cell detachment was similar to that caused by a mixture of albumin and fibronectin. Albumin adsorption did not affect the detachment of cells, while fibronectin adsorption inhibited it. The results of the present study indicate that a pattern-grafted, thermoresponsive, azidophenyl-derivatized copolymer can effectively facilitate selective cell detachment under some conditions such as serum-free culture or preadsorption of albumin. The pattern-grafting technique will be useful for qualitative microscopic comparison of surfaces prepared differently on one chip under the same conditions.

Acrylamides↗
PubMed1999

Osteoclast adhesion and activity on synthetic hydroxyapatite, carbonated hydroxyapatite, and natural calcium carbonate: relationship to surface energies.

This study investigates the adhesion, cytoskeletal changes, and resorptive activity of disaggregated rat osteoclasts cultured on polished slices of three biomaterials: crystalline synthetic hydroxyapatite (HA), carbonated hydroxyapatite (C-HA), and natural calcium carbonate (C). The surface chemistry of each substrate was defined by X-ray diffraction and IR spectroscopy, surface wettability by the dispersive, and the polar components of the surface energies. Osteoclast adhesion was modulated by the polar component of the surface energy: fewer (p < 0.01) osteoclasts adhered to C-HA (97 +/- 20/slice, surface energy 9 +/- 5 mJ/m2) than to HA (234 +/- 16/slice, surface energy 44 +/- 2 mJ/m2) or to C (268 +/- 37/slice, surface energy 58 +/- 0.5 mJ/m2). Actin rings, which are the cytoskeletal structure essential for resorption, developed on all three materials. The area of the actin ring, which is resorbed by local acidification, and the osteoclast area, which reflects osteoclast spreading, were both greater in osteoclasts cultured on HA and C-HA than in those cultured on C. C was resorbed, but HA and C-HA were not. Thus, the surface energy plays an essential role in osteoclast adhesion, whereas osteoclast spreading may depend on the surface chemistry, especially on protein adsorption and/or on newly formed apatite layers. Resorption may be limited to the solubility of the biomaterial.

Actins↗
PubMed1999

Hydrophobicity, surface tension, and zeta potential measurements of glass-reinforced hydroxyapatite composites.

Wettability and zeta potential studies were performed to characterize the hydrophobicity, surface tension, and surface charge of P2O5-glass-reinforced hydroxyapatite composites. Quantitative phase analysis was performed by the Rietveld method using GSAS software applied to X-ray diffractograms. Surface charge was assessed by zeta potential measurements. Protein adsorption studies were performed using vitronectin. Contact angles and surface tensions variation with time were determined by the sessile and pendent drop techniques, respectively, using ADSA-P software. The highest (-18.1 mV) and lowest (-28.7 mV) values of zeta potential were found for hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP), respectively, with composite materials presenting values in between. All studied bioceramic materials showed similar solid surface tension. For HA and beta-TCP, solid surface tensions of 46.7 and 45.3 mJ/m2, respectively, were obtained, while composites presented intermediate surface tension values. The dispersive component of surface tension was the predominant one for all materials studied. Adhesion work values between the vitronectin solution and HA and beta-TCP were found to be 79.8 and 88.0 mJ/m2, respectively, while the 4.0 wt % glass composites showed slightly lower values than the 2.5 wt % ones. The presence of beta-TCP influenced surface charge, hydrophobicity, and protein adsorption of the glass-reinforced HA composites, and therefore indirectly affected cell-biomaterial interactions.

Adsorption↗
PubMed1999

Surface photograft polymerization on segmented polyurethane using the iniferter technique.

A segmented polyurethane (SPU) film was chloromethylated and subsequently dithiocarbamated. The treated films were immersed in solutions containing poly(ethylene glycol) methacrylate (PEGMA) or N, N-dimethyl-acryl amide (DMAAm) and irradiated with ultraviolet (UV) light. The resultant surfaces were highly wettable with water. The surface chemical compositions, as determined by X-ray photoelectron spectroscopy, indicated that surface graft polymerization, initiated from surface-derivatized dithiocarbamate, had occurred and had altered the surface properties and the composition of SPU. The platelet adhesion test using platelet-rich plasma showed minimal adhesion for the poly(PEGMA)-grafted surface, followed by the poly(DMAAm)-grafted surface.

Animals↗
PubMed2000

Calcium phosphate deposition on titanium surfaces in the presence of fibronectin.

Titanium implants are known to nucleate spontaneously a calcium phosphate (apatite-like) layer when in contact with biological model fluids. The presence of proteins either in solution or pre-adsorbed on the titanium surface may influence the process of calcium phosphate deposition. The role of fibronectin, a protein known to promote cell adhesion in spite of its low concentration in biological fluids, was dissolved in Hanks' balanced salt solution (HBSS) and investigated. Several techniques of surface analysis, namely wettability, XPS, and SEM studies, were applied. The concentration of fibronectin in the HBSS solution was an important parameter in the process of calcium phosphate deposition. Concentrations as low as 0.01 mg/mL did not significantly affect the ionic precipitation; however, if the protein concentration was increased to 0.05 mg/mL, a value still far below the concentration in blood (0.2 mg/mL), the formation of a calcium phosphate layer was strongly inhibited. The influence of fibronectin pre-adsorbed on titanium surface also was investigated. It was found, as in the first case, that the extent of ionic precipitation that occurred during the immersion in HBSS depended on the protein concentration in the NaCl solution used to pre-immerse the titanium sample.

Animals↗
PubMed2000

Relationships among cell attachment, spreading, cytoskeletal organization, and migration rate for anchorage-dependent cells on model surfaces.

Many research and commercial applications use a synthetic substrate which is seeded with cells in a serum-containing medium. The surface properties of the material influence the composition of the adsorbed protein layer, which subsequently regulates a variety of cell behaviors such as attachment, spreading, proliferation, migration, and differentiation. In this study, we examined the relationships among cell attachment, spreading, cytoskeletal organization, and migration rate for MC3T3-E1 osteoblasts on glass surfaces modified with -SO(x), -NH(2), -N(+)(CH(3))(3), -SH, and -CH(3) terminal silanes. We also studied the relationship between cell spread area and migration rate for a variety of anchorage-dependent cell types on a model polymeric biomaterial, poly(acrylonitrile-vinylchloride). Our results indicated that MC3T3-E1 osteoblast behavior was surface chemistry dependent, and varied with individual functional groups rather than general surface properties such as wettability. In addition, cell migration rate was inversely related to cell spread area for MC3T3-E1 osteoblasts on a variety of silane-modified surfaces as well as for different anchorage-dependent cell types on a model polymeric biomaterial. Furthermore, the data revealed significant differences in migration rate among different cell types on a common polymeric substrate, suggesting that cell type-specific differences must be considered when using, selecting, or designing a substrate for research and therapeutic applications.

3T3 Cells↗
PubMed2000

Behavior of human osteoblastic cells on stoichiometric hydroxyapatite and type A carbonate apatite: role of surface energy.

To determine the role of physicochemical characteristics of the surface of dense ceramics on osteoconduction, we studied the proliferation and differentiation of human trabecular (HT) osteoblastic cells, extracellular collagenous matrix production, and biologic apatite formation on stoichiometric hydroxyapatite (HA) and type A carbonate apatite (CA). The surface physicochemical characteristics (composition, roughness) of HA and CA carefully were determined by Fourier-transformed infrared, X-ray photoelectron, and Raman spectroscopies, and by FTIR microscopy, before and after cell culture. On both HA and CA substrates, HT cells attached, proliferated, and differentiated. Cell proliferation did not differ on HA and CA. However, the initial cell attachment and spreading of HT cells were much lower on CA compared to HA. Physicochemical and biologic analyses showed that collagenous synthesis by HT cells after 6 weeks of culture also was lower on CA than on HA. Quantitative histologic analysis confirmed that the collagenous matrix production was lower on CA than on HA. Measurement of wettability showed that the polar interaction energy with water was significantly lower on CA than on HA. The lower cell attachment and collagen production on CA compared to HA clearly were related to the low affinity of HT cells for the CA surface. This study shows that the surface energy of the biomaterial greatly influences the initial cell attachment and spreading of human osteoblastic cells at the surface and affects collagenous matrix deposition on the biomaterial. This suggests that the enhancement of polar components of the surface of dense biomaterials may improve osteoblastic cell attachment and, thereby, osteoconduction.

Apatites↗
PubMed2000

A biodegradable hybrid sponge nested with collagen microsponges.

A biodegradable hybrid sponge of poly(DL-lactic-co-glycolic acid) (PLGA) and collagen was fabricated by forming microsponges of collagen in the pores of PLGA sponge. Observation of the PLGA-collagen hybrid sponge by scanning electron microscopy (SEM) showed that microsponges of collagen with interconnected pore structures were formed in the pores of PLGA sponge. The hybrid structure further was confirmed by scanning electron microscopy-electron probe microanalysis (SEM-EPMA), and elemental nitrogen was detected in the microsponges of collagen and on the pore surfaces of PLGA, but not in cross-sections of PLGA regions. The formation of collagen microsponges was dependent on collagen concentration, the effective range of which was from 0.1 to 1.5 (w/v) %. The mechanical strength of the hybrid sponge was higher than that of either PLGA or collagen sponges, in both dry and wet states. The wettability with water was improved by hybridization with collagen, which facilitated cell seeding in the hybrid sponge. Mouse fibroblast L929 cells attached well and spread on the surfaces of the microsponges of collagen in the hybrid sponge. The distribution of cells was spatially uniform throughout the hybrid sponge. Use of the PLGA sponge as a skeleton facilitated formation of the hybrid sponge into desired shapes with high mechanical strength while collagen microsponges contributed good cell interaction and hydrophilicity.

Animals↗
PubMed2000

Anodic oxidation and hydrothermal treatment of titanium results in a surface that causes increased attachment and altered cytoskeletal morphology of rat bone marrow stromal cells in vitro.

Previous studies have suggested the usefulness of a new coating method-namely, the forming of a thin hydroxyapatite (HA) layer on commercially pure titanium (cpTi) by anodization and hydrothermal treatment-for use as a dental root implant material. In vivo and in vitro studies confirmed that an HA layer on cpTi (HA/cpTi) implants showed good compatibility with bone tissue, rat bone marrow stromal (RBM) cells, and immune cells. The aim of the present investigation was to further characterize the in vitro early cellular behavior of RBM cells on HA/cpTi implants. Therefore, in this study we performed surface analysis, analysis of cell initial attachment, and analysis of cell morphology and the cytoskeleton. Drops of distilled water or cell culture medium showed smaller contact angles with HA/cpTi than with cpTi. RBM cells were cultured for 30, 60, and 120 min on HA/cpTi and cpTi, and the level of cell adhesion was shown to increase with time on both substrates. However, cell adhesion on HA/cpTi was significantly higher than on cpTi at 60 and 120 min. Especially at 120 min, when compared with cpTi, the cell morphology on the surface of HA/cpTi not only adopted a flattened and spreading form, but also extended filopodium-like processes with irregular edges that were intimately adapted to the surface of the HA microcrystals. The cytoskeleton on HA/cpTi showed well-formed actin filaments that were parallel to each other and the long axis of RBM cells. The actin filaments of RBM cells on the HA/cpTi surface were localized to the periphery (corresponding to the edge of the filopodium-like processes) well after 120 min. This suggests that actin filaments of RBM cells need to be anchored at the HA/cpTi surface and the numerous HA microcrystals precipitated on the HA/cpTi surface. These findings were similar to the scanning electron microscopic morphology. The peripheral anchorage provide sufficient strength of attachment to allow recognization of actin filaments upon HA/cpTi. The surface of HA/cpTi was more hydrophilic and exhibited markedly improved wettability compared to untreated cpTi, and higher levels of early cell attachment were observed on surfaces after anodization and hydrothermal treatment than on surfaces with untreated cpTi. The results of in vitro experiments suggest that this new method for forming a thin HA layer on the surface of cpTi could be useful to ensure excellent cellular behavior on implant surfaces. The characterization of cell morphology on the thin HA layer formed by anodization and hydrothermal treatment on cpTi implant material suggests that physicochemical or biological conditioning of the implant surface involves implant surface topography.

Animals↗
PubMed2000

Peripheral nerve regeneration using bioresorbable macroporous polylactide scaffolds.

The ability of DRG-derived neurons to survive and attach onto macroporous polylactide (PLA) foams was assessed in vitro. The foams were fabricated using a thermally induced polymer-solvent phase separation. Two types of pore structures, namely oriented or interconnected pores, can be produced, depending on the mechanism of phase separation, which in turn can be predicted by the thermodynamics of the polymer-solvent pair. Coating of the porous foams with polyvinylalcohol (PVA) considerably improved the wettability of the foams and allowed for cell culture. The in vitro biocompatibility of the PVA-coated supports was demonstrated by measuring cell viability and neuritogenesis. Microscopic observations of the cells seeded onto the polymer foams showed that the interconnected pore networks were more favorable to cell attachment than the anisotropic ones. The capacity of highly oriented foams to support in vivo peripheral nerve regeneration was studied in rats. A sciatic nerve gap of 5-mm length was bridged with a polymer implant showing macrotubes of 100 microm diameter. At 4 weeks postoperatively, the polymer implant was still present. It was well integrated and had restored an anatomic continuity. An abundant cell migration was observed at the outer surface of the polymer implant, but not within the macrotubes. This dense cellular microenvironment was found to be favorable for axogenesis.

Animals↗
PubMed2001

Cell behavior on laser surface-modified polyethylene terephthalate in vitro.

This work has been undertaken to study the cell behavior of L929 fibroblasts on the laser irradiated polyethylene terephthalate (PET) surface. To modify the surface properties of the PET, CO2 pulsed laser at the wavelength of 9.25 microm and KrF excimer laser at 248 nm with various number of pulses were used. Laser irradiation caused some changes in the chemical and physical properties of the laser-treated film surfaces, which were evaluated using different techniques. These changes may affect the cell adhesion and growth on the laser-treated PET. Therefore, cell attachment and spreading were investigated on the laser-treated PET in vitro. The data from in vitro assays showed the fibroblast cells were attached and proliferated extensively on the CO2 and KrF laser-treated films in comparison with the unmodified PET. The results obtained from the cell behavior studies revealed that surface morphology and wettability affected cell adhesion and spreading on the laser-treated PET.

Animals↗
PubMed2001

Power consumption profiles in high-shear wet granulation. I: Liquid distribution in relation to powder and binder properties.

Wet granulation processes frequently rely on the device power consumption profile to monitor the process endpoint. This work shows how the observed power consumption relates to the physical properties of the mass. The liquid binder was traced with a fluorescent marker and the liquid distribution could be followed during the process. It was found that primary agglomerates form in the reactor, the shape and composition of which depend on the wettability of the starting powders by the liquid binder. An increase of the device power consumption is conditional to the disruption of these primary agglomerates. Increasing the viscosity of liquid binders up to 250 mPa. s had no significant effect on the power consumption. Eventually, the lower surface tension liquid binders yielded greater energy consumption, indicating that interparticle friction forces had a great impact on the device power consumption.

Chemistry, Pharmaceutical↗
PubMed2001

Influencing the binding selectivity of self-assembled cyclodextrin monolayers on gold through their architecture.

Cyclodextrin derivatives modified with seven thioether moieties (1) or with one thiol moiety (2) bind to gold. Monolayers on gold of 1 or mixed monolayers of 2 and mercaptoundecanol were characterized by electrochemistry, wettability, and atomic force microscopy (AFM). Monolayers of 1 are well-ordered, but the order in the mixed monolayers depends on the ratio of 2 to mercaptoundecanol. With sufficient alkyl chains to fill the space under the cyclodextrin moiety of 2, the monolayers are densely packed. Guest recognition at these monolayers in water was studied by surface plasmon resonance (SPR) spectroscopy. For simple organic guests, monolayers of 1 showed the same selectivity and binding strength as beta-cyclodextrin in solution: however, the selectivity towards steroidal bile salts differs from solution. The mixed monolayers of 2, in which the cyclodextrin is less substituted and has more flexibility, bind steroidal guests (6a-6e) with the same selectivity as beta-cyclodextrin in solution.

Carbohydrate Conformation↗
PubMed2002

Surface oxidation of carbon nanofibres.

Carbon nanofibres of the fishbone and parallel types were surface-oxidised by several methods. The untreated and oxidised fibres were studied with infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy (XPS). Oxidation in a mixture of concentrated nitric and sulfuric acids proved to be the most effective method for creating oxygen-containing surface groups. This treatment results not only in the formation of carboxy and carboxyic anhydride groups, but also in the generation of ether-type oxygen groups between graphitic layers that are puckered at their edges. The IR spectroscopic data clearly show that the formation of oxygen-containing surface groups occurs at defect sites on the carbon nanofibres and that oxidation proceeds via carbonyl groups and other oxides to carboxy and carboxyic anhydride groups. Owing to the presence of defects, the two types of fibre have similar surface reactivities. With parallel nanofibres, in contrast to fishbone fibres, the macroscopic structure was severely affected by treatment with HNO(3)/H(2)SO(4). The HNO(3)/H(2)SO(4)-treated fibres are highly wettable by water.

Journal Article↗
PubMed2003

Host-guest antenna materials.

The focus of this review is on host-guest composites with photonic antenna properties. The material generally consists of cylindrical zeolite L crystals the channels of which are filled with dye molecules. The synthesis is based on the fact that molecules can diffuse into individual channels. This means that, under the appropriate conditions, they can also leave the zeolite by the same way. In some cases, however, it is desirable to block their way out by adding a closure molecule. Functionalization of the closure molecules allows tuning of, for example, wettability, refractive index, and chemical reactivity. The supramolecular organization of the dyes inside the channels is a first stage of organization. It allows light harvesting within a certain volume of a dye-loaded nanocrystalline zeolite and radiationless transport to both ends of the cylinder or from the ends to the center. The second stage of organization is the coupling to an external acceptor or donor stopcock fluorophore at the ends of the channels, which can trap or inject electronic excitation energy. The third stage of organization is the coupling to an external device through a stopcock molecule. The wide-ranging tunability of these highly organized materials offers fascinating new possibilities for exploring excitation-energy-transfer phenomena, and challenges for developing new photonic devices.

Journal Article↗
PubMed2003

Physicochemical and blood compatibility characterization of polypyrrole surface functionalized with heparin.

A surface modification technique was developed for the covalent immobilization of heparin onto electrically conductive polypyrrole (PPY) film. The PPY film was first graft copolymerized with poly(ethylene glycol) methacrylate (PEGMA) and then activated with cyanuric chloride (CC). Heparin was then immobilized onto the film through the reaction between the chloride groups of CC and the amine and/or hydroxyl groups of heparin. X-ray photoelectron spectroscopy (XPS) was used to characterize the surface-modified film after each stage. The biocompatibility of the surface-modified PPY was evaluated using plasma recalcification time (PRT) and platelet adhesion. After surface modification, the film had improved wettability while retaining significant electrical conductivity. With immobilized heparin, platelet adhesion and platelet activation on PPY film was significantly suppressed, and the PRT was significantly prolonged. Electrical stimulation also plays a positive role in decreasing platelet adhesion and increasing PRT on pristine and surface-modified PPY films.

Adsorption↗
PubMed2006

Surfactant-assisted hollowing of Cu nanoparticles involving halide-induced corrosion-oxidation processes.

We have demonstrated a simple fabrication of hollow nanoparticles by halide-induced corrosion oxidation with the aid of surfactants. Cuprous oxide Cu2O nanoshells can be generated by simply mixing Cu nanoparticles with alkyltrimethylammonium halides at 55 degrees C for 16 min. The hollowing mechanism proposed is that absorption of surfactants onto the Cu surface facilitates the formation of the void interior through an oxidative etching process. Upon extending the reaction up to 4 h, fragmentation, oxidation, and self-assembly were observed and the CuO ellipsoidal structures were formed. The headgroup lengths of the surfactants influenced the degree of CuO ellipsoidal formation, whereby longer surfactants favored the generation of ellipsoids. Optical absorption measured by UV-visible spectroscopy was used to monitor both oxidation courses of Cu-->Cu2O and Cu2O-->CuO and to determine the band-gap energies as 2.4 eV for Cu2O nanoshells and 1.89 eV for CuO ellipsoids. For the contact-angle measurements, the wettability changed from hydrophilicity (18 degrees) to hydrophobicity (140 degrees) as the Cu2O nanoshells shifted to CuO ellipsoids.

Bromides↗