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PubMed2003

Genotoxicity of benomyl and its residues in somatic and germ cells of mice fed on treated stored wheat grains.

Swiss mice were fed for 2, 4 and 8 weeks wheat grains treated with 1, 2, and 4 g benomyl/kg and stored for 6 and 12 weeks. The maximum effect of benomyl on the induction of chromosomal aberrations was observed after feeding mice for 8 weeks with wheat grains treated with 4 g benomyl/kg and stored for 12 weeks. Its proportion differed significantly in bone marrow and spermatocyte cells, 15+/-0.51% vs. 13.4+/-0.66%, respectively, from that in nontreated mice (background level), 4.4+/-0.24% and 3.8+/-0.20%, respectively. Lengthening the storage period of treated wheat grains caused a dose-dependent increase in the frequency of sister chromatid exchanges: 8.61+/-0.34 vs. 4.16+/-0.06/cell. The proportion of sperm-head abnormalities increased by lengthening the period of storage and feeding: 7.7+/-0.41% vs. 3.25+/-0.12%. In another experiment mice were orally treated by gavage with benomyl at 50, 100, 150, 200 mg/kg; a significant and dose-dependent increase in sperm-head abnormalities was observed. These findings demonstrate that benomyl (a 50% wettable powder formulation) and its residues in wheat grains are genotoxic in mice.

Animal Feed↗
PubMed2002

Adhesion promotion of Cu on C by Cr intermediate layers investigated by the SIMS method.

Copper-carbon composites are candidate materials for heat sinks for high speed/high-performance electronic components. They combine high thermal conductivity with low density and a tailorable coefficient of thermal expansion (CTE). Because of the low wettability of carbon by copper, a thin layer of chromium can be deposited to promote both the adhesion and the thermal contact of copper with the carbon fibers. Therefore, in a first step layers of Cr and Cu were deposited by magnetron sputtering on plane vitreous carbon substrates (Sigradur G), which serve as a model for carbon fibers. From pull-off-adhesion measurements an interlayer thickness of Cr in the range of 2-10 nm was found to provide the optimal adhesion for 1 micro m thick copper overlayers. To model the later serial fabrication of the composite that involves a hot pressing step following the deposition, the C/Cr/Cu samples were heat treated at 800 degrees C under vacuum for 1 h. Adhesion on the heat-treated samples was superior in comparison to the untreated ones. To obtain information about the adhesion mechanism secondary ion mass spectrometry (SIMS) investigations were done on the depth distribution of the main elements copper, chromium, and carbon. Two samples, one as deposited and one subjected to heat treatment after deposition, were compared in this investigation. We found that heat treatment mainly modifies the distribution of Cr in the C/Cr/Cu system.

Journal Article↗
PubMed2006

Amperometric hydrogen peroxide sensor based on a sol-gel-derived ceramic carbon composite electrode with toluidine blue covalently immobilized using 3-aminopropyltrimethoxysilane.

A carbon composite amperometric hydrogen peroxide sensor has been developed using a sol-gel technique. Toluidine blue (TB), which acts as the redox mediator, was covalently immobilized via glutaraldehyde crosslinking with an organically modified silane, namely 3-aminopropyltrimethoxysilane (APTMOS). Methyltrimethoxysilane (MTMOS) was used as the additional monomer; this controls the hydrophobicity of the electrode surface, thus limiting the wettability. The immobilization of TB within the sol-gel matrix was confirmed with FTIR studies. The sol-gel mixture containing TB immobilized in APTMOS and MTMOS was mixed with graphite powder in order to prepare the carbon composite electrode. The electrode was characterized using voltammetric techniques and its electrocatalytic activity for the reduction of hydrogen peroxide was also studied. The carbon composite electrode has the advantage of sensing H(2)O(2) at a lower potential and with a higher sensitivity, and interferences due to ascorbic acid, uric acid and acetaminophen were greatly minimized. The linear range for the determination of H(2)O(2) extends from 5.37 x 10(-6) to 6.15 x 10(-3) M, with a correlation coefficient of 0.9981. The detection limit was found to be 2.15 x 10(-6) M. The covalent immobilization of TB effectively prevents the leakage of the water-soluble mediator during measurements. The modified electrode, aside from electrocatalyzing the reduction of H(2)O(2), exhibits distinct advantages in terms of surface renewal in the event of surface fouling, as well as simple preparation, good chemical and mechanical stability, and good reproducibility.

Biosensing Techniques↗
PubMed1995

EPMA of interfaces applied to the solid oxide fuel cell.

Chemical interactions at the phase boundaries of materials applied for the solid oxide fuel cell (SOFC) have been studied by EPMA. The chemical reactivity at the interface of La(y-x)Sr(x)MnO(3)/ZrO(2)-Y(2)O(3) is dependent on the stoichiometry (y) and the Sr content (x) of the perovskite. Typical reaction products (zirconates) and a diffusion zone in the ZrO(2)-Y(2)O(3) have been observed. The extension of cation release (Mn) is related to the increasing chemical activity of Mn oxide in the perovskite by the Sr substitution for La. The wettability of the metal/oxide interface in the anode cermet (Ni/ZrO(2)-Y(2)O(3)) has been found to be influenced by chemical reactions resulting from the applied reducing atmosphere with high carbon activity. The disintegration of ZrO(2)-Y(2)O(3) in contact with molten Ni or Ni-Ti and Ni-Cr alloys leads to the redeposition of Y(2)O(3)-enriched oxides and also to Zr-rich intermetallic compounds and eutectics.

Journal Article↗
PubMed2000

Plant-Microbe Interactions: Wetting of Ivy (Hedera helix L.) Leaf Surfaces in Relation to Colonization by Epiphytic Microorganisms.

Leaf wettability, cuticular wax composition, and microbial colonization of upper and lower leaf surfaces of ivy (Hedera helix L.) was investigated for young and old leaves sampled in June and September. Contact angles of aqueous buffered solutions measured on young leaf surfaces ranged between 76° and 86° and were not dependent on the pH value of the applied droplets. Contact angles measured on old leaf surfaces were up to 32°, significantly lower than on young leaf surfaces. Furthermore, contact angles were significantly lower using aqueous solutions of pH 9.0 compared to pH 3.0, indicating the influence of ionizable functional groups on leaf surface wetting properties. Observed changes in leaf wetting properties did not correlate with different levels of alkanoic acids in cuticular waxes. However, microscopic examination of the leaf surfaces indicated the influence of epiphytic microorganisms on wetting properties of old leaves, since their surfaces were always colonized by epiphytic microorganisms (filamentous fungi, yeasts, and bacteria), whereas surfaces of young leaves were basically clean. In order to analyze the effect of epiphytic microorganisms on leaf surface wetting, surfaces of young and clean ivy leaves were artificially colonized with Pseudomonas fluorescens. This resulted in a significant increase and a pH dependence of leaf surface wetting in the same way as it was observed on old ivy leaf surfaces. From these results it can be deduced that the native wetting properties of leaf surfaces can be significantly masked by the presence of epiphytic microorganisms. The ecological implications of altered wetting properties for microorganisms using the leaf/atmosphere interface as habitat are discussed.

Journal Article↗
PubMed2006

An ethoxylated alkyl phosphate (anionic surfactant) for the promotion of activities of proteases and its potential use in the enzymatic processing of wool.

Pretreatments of wool fabrics with cationic, anionic or non-ionic surfactants were investigated to reduce surface tension and improve the wettability of the fibres in order to promote protease activity on the fibres in subsequent processes. Results showed that an ethoxylated alkyl phosphate (specific anionic surfactant) as well as the widely used non-ionic surfactant was compatible with proteases in the enzymatic treatment of wool. There is therefore a potential for using specific anionic surfactants to achieve efficient enzymatic scouring processes.

Animals↗
PubMed2006

Early responses to acute ozone exposure in two Fagus sylvatica clones differing in xeromorphic adaptations: photosynthetic and stomatal processes, membrane and epicuticular characteristics.

Two Fagus sylvatica L. clones were used to investigate the early responses to acute O3 exposure (150 nL L(-1), i.e., 1.35x ambient hourly peak in rural Italy) and whether xeromorphic adaptations affect gas exchange, membrane, and epicuticular responses. One clone originated in a wet and temperate climate in Central Italy (Tuscany); the other clone originated in a warmer and drier climate in the southern-most part of the F. sylvatica distribution (Sicily). Because of higher base gas exchange rates, the most negative effects of O3 exposure (gas exchange impairment, uncoupling between net photosynthesis and stomatal conductance, increased membrane lipid peroxidation) were found in the southern clone. Xeromorphic adaptations (higher epicuticular waxes and stomatal density, lower leaf wettability and size) were found in this clone. Our results suggest that xeromorphism may increase O3 sensitivity in species not adapted to face water stress, like the mesophilic F. sylvatica, when experiments are carried out with full irrigation. We present evidence describing the relationship between gas exchange and number and status of stomata. Stomatal density and the structural damage to stomata resulting from O3 exposure did not affect gas exchange: In fact, non-stomatal limitations to photosynthesis prevailed over stomatal limitations.

Adaptation, Physiological↗
PubMed2005

TiO2 type influences fibronectin adsorption.

Human fibronectin (FN) plays a key role in the biointegration of implants as the success depends on adsorption of proteins like FN [1]. Indeed FN can be an intermediary between the biomaterial surface and cells. The adsorption of human fibronectin (FN) on commercially pure titanium with a titanium oxide layer formed in a H2O2 solution (TiO2 cp) and TiO2 sputtered on Si (TiO2 sp) was studied. Adsorption isotherms and the work of adhesion were assessed by wettability studies, X-ray photoelectron spectroscopy (XPS), and by radiolabelling of FN with 125I, (125)I-FN. Exchangeability of bound FN by free FN, was also evaluated by the radiolabelling technique. Contact angle determinations have shown that FN displays higher affinity for the TiO2 cp surface than for the TiO2 sp. As expected from the surface free energy values, the work of adhesion of FN is higher for the TiO2 cp substrate, the more hydrophilic one, and lower for the TiO2 sp substrate, the more hydrophobic one. The adsorption isotherms were evaluated by two different techniques: radiolabelling of FN (125I-FN) and XPS. TiO2 cp adsorbs more FN than the TiO2 sp surfaces as shown by the radiolabelling data. FN molecules are also more strongly attached to the former surface as indicated by the work of adhesion and by the exchangeability studies. Results using 125I-FN also suggests that FN adsorbs as a multilayer for FN concentrations in solution higher than 100 microg/mL.

Adsorption↗
PubMed2005

The effect of starch-based biomaterials on leukocyte adhesion and activation in vitro.

Leukocyte adhesion to biomaterials has long been recognised as a key element to determine their inflammatory potential. Results regarding leukocyte adhesion and activation are contradictory in some aspects of the material's effect in determining these events. It is clear that together with the wettability or hydrophilicity/hydrophobicity, the roughness of a substrate has a major effect on leukocyte adhesion. Both the chemical and physical properties of a material influence the adsorbed proteins layer which in turn determines the adhesion of cells. In this work polymorphonuclear (PMN) cells and a mixed population of monocytes/macrophages and lymphocytes (mononuclear cells) were cultured separately with a range of starch-based materials and composites with hydroxyapatite (HA). A combination of both reflected light microscopy and scanning electron microscopy (SEM) was used in order to study the leukocyte morphology. The quantification of the enzyme lactate dehydrogenase (LDH) was used to determine the number of viable cells adhered to the polymers. Cell adhesion and activation was characterised by immunocytochemistry based on the expression of several adhesion molecules, crucial in the progress of an inflammatory response. This work supports previous in vitro studies with PMN and monocytes/macrophages, which demonstrated that there are several properties of the materials that can influence and determine their biological response. From our study, monocytes/macrophages and lymphocytes adhere in similar amounts to more hydrophobic (SPCL) and to moderately hydrophilic (SEVA-C) surfaces and do not preferentially adhere to rougher substrates (SCA). Contrarily, more hydrophilic surfaces (SCA) induced higher PMN adhesion and lower activation. In addition, the hydroxyapatite reinforcement induces changes in cell behaviour for some materials but not for others. The observed response to starch-based biodegradable polymers was not significantly different from the control materials. Thus, the results reported herein indicate the low potential of the starch-based biodegradable polymers to induce inflammation especially the HA reinforced composite materials.

Biocompatible Materials↗
PubMed2005

Optimization of gold nanoparticle-based DNA detection for microarrays.

DNA microarrays are promising tools for fast and highly parallel DNA detection by means of fluorescence or gold nanoparticle labeling. However, substrate modification with silanes (as a prerequisite for capture DNA binding) often leads to inhomogeneous surfaces and/or nonspecific binding of the labeled DNA. We examined both different substrate cleaning and activating protocols and also different blocking strategies for optimizing the procedures, especially those for nanoparticle labeling. Contact angle measurements as well as fluorescence microscopy, atomic force microscopy (AFM), and a flatbed scanner were used to analyze the multiple-step process. Although the examined different cleaning and activating protocols resulted in considerably different contact angles, meaning different substrate wettability, silanization led to similar hydrophobic surfaces which could be revealed as smooth surfaces of about 2-4 nm roughness. The two examined silanes (3-glycidoxypropyltrimethoxysilane (GOPS) and 3-aminopropyltriethoxysilane (APTES)) differed in their DNA binding homogeneity, maximum signal intensities, and sensitivity. Nonspecific gold binding on APTES/PDC surfaces could be blocked by treatment in 3% bovine serum albumin (BSA).

Base Sequence↗
PubMed2006

Investigation of wetting behavior of nonaqueous ethylcellulose gel matrices using dynamic contact angle.

PURPOSE: This study reports the development of a method based on dynamic contact angle to investigate the wetting behavior of non-aqueous ethylcellulose (EC) gel matrices intended for topical drug delivery. METHODS: Non-aqueous gel matrices were prepared from the three fine particle grades of EC and propylene glycol dicaprylate/dicaprate. Dynamic contact angle measurements of sessile drops of water and isopropylmyristate (IPM) on EC gel matrices were performed using a dynamic contact angle analyzer equipped with axisymmetric drop shape analysis of the sessile drop images. Gel density was determined by weighing known volumes of gel samples. RESULTS: The EC gel matrices were wetted by both water and IPM, with much higher wettability by the latter. Increased EC concentration and polymeric chain length decreased the extent and rate of wetting. Linear correlation was observed between wetting parameters and rheological as well as mechanical properties of EC gel matrices. CONCLUSIONS: The EC gel matrices exhibited both hydrophilic and lipophilic properties, with predominance of the latter. The extent and rate of wetting was governed by a balance of chemical and physical characteristics of the gel. EC gel matrices showed desirable wetting behavior in their function as a moisture-barrier, bioadhesive and vehicle for topical drug delivery.

Adhesiveness↗
PubMed1989

Variation in human salivary pellicle formation on biomaterials during the day.

Contact angle measurements were used to study the effects of pellicle formation on polymethyl-methacrylate, dental amalgam and gold. Samples were exposed to saliva in vivo for periods of 5-20 min at three separate occasions during the day. Pellicle drastically increased the wettability of all the materials and effectively sealed off the effect of the original surface activity. Variation in pellicle formation during the day was demonstrated. Pellicles formed at midday showed the least reduction in contact angles compared to those formed during the morning and afternoon. This difference coincided with an increased concentration of inorganic phosphate in saliva at midday. The method enables comparative studies of pellicle formation on hard biosurfaces. The findings indicate differences in the physical behaviour of saliva during the day, and illustrate the importance of making adhesion studies with this variation in mind.

Adhesiveness↗
PubMed1993

Surface determinants of neuronal survival and growth on self-assembled monolayers in culture.

We have studied the modulation of hippocampal neuron morphological development in vitro using surfaces derivatized with aminosilane self-assembled monolayers (SAMs). The efficacies of model SAMs, alone, or in combination with adsorbed heparan sulfate glycosaminoglycan (HS), are related to the physical and chemical properties of the surfaces. These properties are determined using X-ray photoelectron spectroscopy (XPS), optical ellipsometry, and wettability measurements. The ability of surfaces to promote somal adhesion and the maintenance of discrete neurites appears to be sensitive to the density and accessibility of positively charged amine or amide groups, and has less of an apparent relationship to the surface density of uncharged amines. Aromatic ring-containing aminosilanes are ineffective in promoting neuron growth, while adsorbed HS augments the neurite-promoting capacity of one marginally adhesive SAM. These results are relevant to an improved understanding of the 'non-specific' contributions of the substrate in affecting neuronal development and the rational design of model surface coatings for neuronal culture.

Animals↗
PubMed1990

Morphological effects of aspirin and prostaglandin on the canine gastric mucosal surface. Analysis with a phospholipid-selective cytochemical stain.

An iodoplatinate technique that selectively stains phospholipid was used to evaluate morphologically the effects of aspirin and 16,16-dimethyl prostaglandin E2 on canine gastric mucosa in an in vitro Ussing chamber system. The association between these morphological alterations and the changes in mucosal surface hydrophobicity as determined by contact angle analysis was also investigated. Prostaglandin (1 microgram/ml) did not alter aspirin-induced cell injury, although it reduced (45%) the detachment of damaged cells from the lamina propria. Mucus release appeared to be stimulated independently both by aspirin and prostaglandin treatment and by the blotting and drying procedure routinely performed before contact angle analysis. When an extracellular mucus gel coat was present, it contained numerous iodoplatinate-reactive vesicles and myelinated or lamellated structures. Iodoplatinate-reactive substances also appeared at the luminal surface of the mucus gel as a filamentous band. This band of reactivity was frequently seen after simultaneous treatment with prostaglandin and aspirin but only sporadically observed after aspirin treatment alone. The hydrophobic nature of the canine gastric mucosa under the above experimental conditions correlated well (r = 0.743, p less than 0.005) with the percentage of mucosal surface covered by this filamentous band, and less so with the density of iodoplatinate-reactive structures within the mucus gel. We conclude that phospholipid structures in the mucus gel may account for the hydrophobic nature of the gastric mucosal surface and the ability of damaging and "cytoprotective" agents to influence both surface wettability and barrier integrity.

Animals↗
PubMed1994

High-performance thin-layer chromatographic determination of digoxin and related compounds, digoxigenin bisdigitoxoside and gitoxin, in digoxin drug substance and tablets.

A high-performance thin-layer chromatographic (HPTLC) method for the determination of digoxin and its related compounds digoxigenin bisdigitoxoside (DBD) and gitoxin in digoxin drug substance and tablets was developed. Separation of the three compounds was accomplished on a C18 wettable reversed-phase plate using water-methanol-ethyl acetate (50:48:2, v/v/v) as the mobile phase. The analytes were determined by densitometry using absorbance for digoxin and fluorescence for the two related compounds. All peaks were quantified by peak-height analysis. Linear regression analysis of the data was performed for all three compounds. The calibration range for digoxin was set at 320-480 ng per 5-mm band, equivalent to 80-120% (w/w) of a 400-ng band load, that for DBD was set at 4-12 ng per 5-mm band, equivalent to 1-3% (w/w) of the digoxin load, and that for gitoxin was set at 0.4-1.6 ng per 5-mm band, equivalent to 0.1-0.4% (w/w) of the digoxin load. The limit of quantification (LOQ) for digoxin was 64 ng per 5-mm band with a limit of detection (LOD) of 8 ng per 5-mm band. The LOQs for both DBD and gitoxin were 0.12 ng per 5-mm band with LODs of 0.4 ng per 5-mm band. The linearity range for the digoxin peak height in the absorbance mode was 0-5000 ng per 5-mm band. The linearity range for DBD and gitoxin peak heights in the fluorescence mode was 0-2000 ng per 5-mm band.

Carbohydrate Sequence↗
PubMed1979

An investigation of tensile strength of dental solder joints.

Tensile specimens of dental solder joints were tested to determine the effect of gap distance on the strength of solder joints. Two dental alloys were used; a Type III gold alloy and a gold-palladium (Au-Pd) alloy. The Type III alloy was joined with the recommended gold solder. The Au-Pd alloy was joined using preceramic and postceramic application soldering techniques. Gap distances of 0.13 mm, 0.5 mm, and 1 mm were used with each soldering technique. All solder specimens were machined to a uniform diameter and then tested for tensile strength. It was concluded that: 1. There was a significant increase in strength for the Type III gold as the gap distance was increased. 2. The trend toward stronger joints at narrow gap distances for Au-Pd alloy joined with presolder was not statistically significant. 3. The trend toward stronger joints at wide gap distances for the Au-Pd alloy joined with the postsolder was not statistically significant. 4. The postsolder joints were statistically stronger than the presolder joints. 5. The trends observed could be partially explained in terms of competing effects of yield strength (triaxially), wettability, and void or inclusion content at the various gap distances.

Dental Alloys↗
PubMed1979

The effect of nonionic surfactants on bubble entrapment in elastomeric impression materials.

The incorporation of certain nonionic surfactants into silicone and polysulfide elastomers increases their wettability by gypsum products and consequently results in less bubble entrapment in poured casts. The choice of the most effective surfactant is critical and differs not only between types of elastomer, but also between brands of a single type. The beneficial effect of the optimal surfactant is not reduced by rinsing the impression prior to pouring. While the working time of silicone is increased by surfactant additions, that of polysulfide is essentially unaffected, as are the dimensional accuracies and permanent deformations of both materials.

Air↗
PubMed1987

Urethane-lined silicone facial prostheses.

After testing a variety of materials to line the tissue-fitting surface of silicone prostheses in an attempt to render them adheophilic, tear-resistant, wettable, smooth, and resistant to fungal growth, a vacuum adaptable thermoplastic prefabricated thin urethane film was found to be most effective. A technique is described for fabricating a silicone prosthesis with such a lining.

Adhesiveness↗