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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Membranes in artificial organs and scaffolds for tissue engineering are often coated with biomimetic molecules (e.g., collagen) to improve their biocompatibility and promote primary cell adhesion and differentiation. However, animal proteins are expensive and may be contaminated with prions. Silk fibroin (SF) made by Bombyx Mori silk worms, used as a scaffold or grafted to other polymers, reportedly promotes the adhesion and growth of many human cell types. This paper describes how commercial porous membranes were physically coated with SF, and their physical-chemical properties were characterized by SEM, AFM, tensile stress analysis and dynamic contact angle measurements. The effect of the SF coating on membrane biocompatibility and resistance to bacterial colonization is also examined. The proposed technique yields SF coats of different thickness that strengthen the membranes and make their surface remarkably more wettable. The SF coat is not cytotoxic, and promotes the adhesion and proliferation of an immortalized fibroblast cell line. Similarly to collagen, SF-coated membranes also exhibit a much better resistance to the adhesion of S. epidermidis bacteria than uncoated membranes. These preliminary results suggest that SF is a feasible alternative to collagen as a biomimetic coating for 3D scaffolds for tissue engineering or bioartificial (as well as artificial) prosthesis.
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PMID:Physical-chemical and biological characterization of silk fibroin-coated porous membranes for medical applications. 1703 96

Crosslinked gels (hylans) containing long-chain (MW>1 x 10(6)Da) hyaluronan (HA), a connective tissue GAG, show exceptional biocompatibility for vascular implantation but poorly interact with vascular endothelial cells (ECs). Previous studies showed in situ fragmentation of HA by UV light to bioactivate hylan gels and elicit enhanced EC responses. Since fragmented HA can be pro-inflammatory, it is important to define an optimal size distribution of HA fragments on the hylan surface that will recruit and support normally functional ECs and limit ulterior responses. Related studies have shown that exogenous models of HA do not necessarily replicate cell responses to HA scaffolds. Since scaffolds cannot be created based on fragmented HA alone, we sought to determine size-specific responses of ECs to HA substrates of defined fragment sizes by creation of HA-tethered culture surfaces. HA (1000, 200, 20 kDa) and an oligomer mixture were tethered onto an aminosilane (APTMS)-treated glass surfaces using a carbodiimide reaction. MALDI-TOF showed the HA digests to contain HA 4-8mers with a 75+/-0.4% w/w of 4mers. Immuno-fluorescence, SEM, AFM and XPS analysis revealed homogeneous amine and HA surfaces. An amine s-SDTB assay and HA fluorophore-assisted carbohydrate electrophoresis (FACE) indicated surface densities of 9+/-3 amine groups/nm(2) and 0.57+/-0.44 microg/cm(2), respectively. HA/HA fragments/oligomers were stable over 21 days of incubation in serum-free culture media. EC proliferation on these surfaces resulted was limited, a possible effect of smooth surface topography, high anionicity, and in case of 4mers, non-interaction with primary HA cell-surface receptors (CD44). This work is significant in that it allows testing of cell responses to substrates composed of single-sized fragments of HA that cannot by themselves be cross-linked into a gel. Future work in our lab will use this model to assess the effects of other HA oligomer sizes on EC behavior.
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PMID:A surface-tethered model to assess size-specific effects of hyaluronan (HA) on endothelial cells. 1704 32

Cortisol is a member of the glucocorticoid hormone family and a key metabolic regulator. Increased intracellular cortisol levels have been implicated in type 2 diabetes, obesity, and metabolic syndrome. Cortisol is an important bio-marker of stress and its detection is also important in sports medicine. However, rapid methods for sensitive detection of cortisol are limited. Functionalized gold nanowires were used to enhance the sensitivity and selectivity of cortisol detection. Gold nanowires are used to improve the electron transfer between the electrodes. Moreover, the large surface to volume ratio, small diffusion time and high electrical conductivity and their aligned nature will enhance the sensitivity and detection limit of the biosensor several fold. The biosensor was fabricated using, aligned gold (Au) nanowires to behave as the working electrode, platinum deposited on a silicon chip to function as the counter electrode, and silver/silver chloride as reference electrode. The gold nanowires were coupled with cortisol antibodies using covalent linkage chemistry and a fixed amount of 3alpha-hydroxysteroid dehydrogenase was introduced into the reaction cell during each measurement to convert (reduce) ketosteroid into hydroxyl steroid. Furthermore, the micro-fluidic, micro-fluid part of the sensor was fabricated using micro-electro-mechanical system (MEMS) technology to have better control on liquid flow over Au nanowires to minimize the signal to noise ratio. The biosensor was characterized using SEM, AFM and FTIR technique. The response curve of the biosensor was found to be linear in the range of 10-80 microM of cortisol. Moreover, the presence of hydrocortisone is sensitively detected in the range of 5-30 microM. It is concluded that the functionalized gold nanowires with micro-fluidic device using enzyme fragment complementation technology can provide an easy and sensitive assay for cortisol detection in serum and other biological fluids.
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PMID:Ultrasensitive detection of cortisol with enzyme fragment complementation technology using functionalized nanowire. 1709 83

Single-walled carbon nanotubes have been functionalized and the specific surface areas of the functionalized nanotubes measured. Contrary to expectations, functionalization leads to a decrease in specific surface area compared to that of the unfunctionalized nanotubes. Treatment with a concentrated 1:1 nitric/sulfuric acid mixture followed by high-temperature baking at 1000 degrees C was found to increase the specific surface area of the nanotubes. For the unfunctionalized SWNTs, this treatment increases the specific surface area (SSA) by 20%. In the case of SWNTs functionalized by n-butyl groups the increase in the SSA was nearly 2-fold with the value increasing from 410 (drying at 110 degrees C) to 770 m2/gm (acid and bake treatment followed by drying at 110 degrees C). For the ozonized SWNTs, the SSA increases more than 3-fold from 381 (drying at 110 degrees C) to 1068 m2/gm (acid and bake treatment followed by drying at 110 degrees C). SEM images indicate that the nanotubes rebundle in the solid state with an average bundle size of 10-30 nm. AFM studies show that the ozonized tubes have been cut to short bundles after ozonolysis. Hydrogen uptake studies carried out on the baked ozonized tubes led to a 3 wt % hydrogen uptake at 77 K and 30 bar.
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PMID:Surface area measurement of functionalized single-walled carbon nanotubes. 1714 98

Mechanical properties of nanoparticle chain aggregates (NCA) including tensile strength and Young's modulus were measured using an instrument incorporating an AFM tip under SEM imaging. The NCA were studied individually and as network films. Carbon NCA were made by laser ablation of graphite, and SnO2 NCA were made by oxidation of a tin compound. The films were deformable and showed elastic behavior. NCA serve as reinforcing fillers in rubber and films of SnO2 NCA for trace gas detection.
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PMID:Mechanical properties of nanoparticle chain aggregates by combined AFM and SEM: isolated aggregates and networks. 1716 82

Staphylococcus epidermidis is the primary cause of medical device-related infections due to its adhesion and biofilm forming abilities on biomaterial surfaces. For this reason development of new materials and surfaces to prevent bacterial adhesion is inevitable. In this study, the adhesion of biofilm forming S. epidermidis strain YT-169a on nitrogen (N) ion implanted as well as on as-polished CoCrMo alloy materials were investigated. A medical grade CoCrMo alloy was ion implanted with 60 keV N ions to a high dose of 1.9 x 10(18) ions/cm(2) at substrate temperatures of 200 and 400 degrees C. The near-surface implanted layer crystal structures, implanted layer thicknesses, and roughnesses were characterized by XRD, SEM and AFM. The number of adherent bacteria on the surfaces of N implanted specimens was found to be 191 x 10(6) CFU/cm(2) for the 200 degrees C and 70 x 10(6) CFU/cm(2) for the 400 degrees C specimens compared to the as-polished specimen (3 x 10(6) CFU/cm(2)). The adhesion test results showed that S. epidermidis strain YT-169a adhere much more efficiently to the N implanted surfaces than to the as-polished CoCrMo alloy surface. This was attributed mainly to the rougher surfaces associated with the N implanted specimens in comparison with the relatively smooth surface of the as-polished specimen.
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PMID:Biofilm formation by Staphylococcus epidermidis on nitrogen ion implanted CoCrMo alloy material. 1718 92

Frechet-type benzyl ether dendrons of second and third generations with a carboxyl group (G2, G3) at the apex site could attach to poly(4-vinylpyridine) (PVP), forming hydrogen-bonded dendronized polymers (HB denpols) in their common solvent, chloroform. The HB denpols show unique self-assembly behavior, forming vesicles in the common solvent under ultrasonic treatment. The structure and morphology of the vesicles were characterized by dynamic light scattering (DLS), static light scattering (SLS), SEM, TEM, and AFM. The size of the vesicles decreases and the thickness of the vascular membrane increases as the molar ratio of Gx/PVP increases. The hydrogen bonding, pi-pi aromatic stacking of the dendrons, and the considerable difference in architecture between the dendron Gx and PVP are the main factors facilitating the assembly of the HB denpols in the common solvent.
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PMID:Hydrogen-bonded dendronized polymers and their self-assembly in solution. 1720 94

Titanium is the most widely used material for dental implants. The natural formation, in presence of oxygen, of different oxide films (passivation films) is correlated to titanium implant biocompatibility, resistance to corrosion and is responsible for implant bacteriostatic action. Surface roughness is another surface property of Ti-implants that, affecting implant-to-bone contact, improves integration. In the present study data concerning composition, surface roughness and biocompatibility of Ghimas implants and mini-implants undergoing sandblasting with Calcium Magnesium Carbonate (CaMg(CO3)2) are reported. AFM, SEM/EDX, XRD analyses and morpho-functional tests (MTT and ALP) were performed. Cell actin cytoskeletal modification (fluorescence phalloidin staining) was also observed with confocal laser microscopy (CLSM). Data related to surface geometry and chemical properties, associated with evidence of high purity of all the tested materials (XRD and EDX), highlighted the elevated biocompatibility of tested implants and mini-implants. CLSM investigation confirmed osteoblast features of an active cell behavior able to fit cell to chemico-mechanical stimuli present at the bone/implant interface and suggests an effective implant/alveolar bone integration in vivo.
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PMID:In vitro evaluation of bio-functional performances of Ghimas titanium implants. 1721 23

Boron doped diamond (BDD) macro- and microelectrodes were modified by electrodeposition of platinum nanoparticles using a multipotential step electrodeposition technique and used for the oxidative determination of arsenite, As(III). The formation of Pt nanoparticles was evident from cyclic voltammetry measurement, whereas AFM and SEM revealed the size and size distribution of deposited Pt nanoparticles. Raman spectroscopy illustrated a correlation between the typical BDD signature and the number of platinum deposition cycles. Linear sweep voltammetry performed with the modified BDD microelectrode outperformed its macrocounterpart and resulted in very low detecting currents with enhanced signal-to-noise ratios. With linearity up to 100 ppb and a detection limit of 0.5 ppb, the electrochemical system was applicable for processing tap and river water samples. Over 150 repetitive runs could be performed, and electrochemical etching of platinum allowed the reuse of the BDD microelectrode. The presence of copper and chloride ions, the two most severe interferents at levels commonly found in groundwater, did not interfere with the assay.
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PMID:Reusable platinum nanoparticle modified boron doped diamond microelectrodes for oxidative determination of arsenite. 1722 13

The present study demonstrates that H(2)O(2) and OH(.-) cause fibril aggregation and catalytic inactivation of porcine fumarase. In the aggregated (oxidized) enzyme, modifications in both secondary and tertiary protein structure occur and the enzyme aggregation obeys to fractal geometry. We then collected information on the fractal dimension and on the size and shape of fumarase aggregates by using Synchrotron Radiation (SR) Small Angle X-ray Scattering (SAXS) analysis. The geometrical self-similarity assessment of aggregates has been revealed by both AFM and SEM measurements at different scale of magnification. Micrographs collected remarkably demonstrate that the oxidized enzyme shows dendritic fractal structure over a large range of sizes.
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PMID:Fractal aggregation of porcine fumarase induced by free radicals. 1724 Feb 6


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