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PubMed2006

Generation of hydrophilic poly(dimethylsiloxane) for high-performance microchip electrophoresis.

Poly(dimethylsiloxane) (PDMS) has become one of the most widely used materials for microchip capillary electrophoresis and microfluidics. The popularity of this material is the result of its low cost, simple fabrication, and rugged elastomeric properties. The hydrophobic nature of PDMS, however, limits its applicability for microchip CE, microfluidic patterning, and other nonelectrophoresis applications. The surface of PDMS can be made hydrophilic using a simple air plasma treatment; however, this property is quickly lost through hydrophobic recovery caused by diffusion of unreacted oligomer to the surface. Here, a simple approach for the generation of hydrophilic PDMS with long-term stability in air is presented. PDMS is rendered hydrophilic through a simple two-step extraction/oxidation process. First, PDMS is extracted in a series of solvents designed to remove unreacted oligomers from the bulk phase. Second, the oligomer-free PDMS is oxidized in a simple air plasma, generating a stable layer of hydrophilic SiO2. The conversion of surface-bound siloxane to SiO2 was followed with X-ray photoelectron spectroscopy. SiO2 on extracted-oxidized PDMS was stable for 7 days in air as compared to less than 3 h for native PDMS. Furthermore, the contact angle for modified PDMS was reduced to <40 degrees and remained low throughout the experiments. As a result of the decreased contact angle, capillary channels self-wet through capillary action, making the microchannels much easier to fill. Finally, the modification significantly improved the performance of the devices for microchip electrophoresis. The electroosmotic flow increased from 4.1 x 10(-4) to 6.8 x 10(-4) cm(2)/V.s for native compared to oxidized PDMS. Separation efficiencies for electrochemical detection also increased from 50 000 to 400 000 N/m for a 1.1-nL injection volume. The result of this modification is a significant improvement in the performance of PDMS for microchip electrophoresis and microfluidic applications.

Dimethylpolysiloxanes↗

PubMed2007

Genotyping of single-nucleotide polymorphisms by primer extension reaction in a dry-reagent dipstick format.

The primer extension (PEXT) reaction is the most widely used approach to genotyping of single-nucleotide polymorphisms (SNPs). Current methods for analysis of PEXT reaction products are based on electrophoresis, fluorescence resonance energy transfer, fluorescence polarization, pyrosequencing, mass spectrometry, microarrays, and spectrally encoded microspheres. We report the first dry-reagent dipstick method that enables rapid visual detection of PEXT products without instrumentation. The method is applied to the analysis of six SNPs in the mannose-binding lectin gene (MBL2). The genomic region that spans each SNP of interest is amplified by PCR. Two primer extension reactions are performed with allele-specific primers (for one or the other variant nucleotide), which contain an oligo(dA) segment at the 5'-end. Biotin-dUTP is incorporated in the extended strand. The product is applied to the strip followed by immersion in the appropriate buffer. As the DNA moves along the strip by capillary action, it hybridizes with oligo(dT)-functionalized gold nanoparticles, such that only extended products are captured by immobilized streptavidin at the test zone, generating a red line. A second red line is formed at the control zone of the strip by hybridization of the nanoparticles with immobilized oligo(dA). The dipstick test is complete within 10 min. We analyzed six SNPs of the mannose-binding lectin gene (MBL2) using genomic DNA from 27 patients, representing a total of 74 variant nucleotide positions. Patient genotypes showed 100% concordance with direct DNA sequencing data. The described PEXT-dipstick assay is rapid and highly accurate; it does not require specialized instrumentation or highly trained technical personnel. It is appropriate for a diagnostic laboratory where a few selected SNP markers are examined per patient with a low cost per assay.

DNA Primers↗

PubMed2000

Direct TLC-MALDI coupling using a hybrid plate.

A new TLC-MALDI direct coupling method which recovers approximately 100% of the analyte is presented. The method makes use of a hybrid TLC-MALDI plate in which a silica layer and a MALDI layer are configured adjacently on a common backing. After TLC separation, the plate is rotated 90 degrees and the separated analyte spots are eluted from the silica layer to the MALDI layer via capillary action of the MALDI layer. Signal-to-noise ratios are significantly improved over previously reported coupling methods. Low-femtomole detection limits have been demonstrated for small cyclic peptides, which are comparable to detection limits for standard MALDI measurements.

Chromatography, Thin Layer↗

PubMed2004

Nanocolloidal gold-based immunoassay for the detection of the N-methylcarbamate pesticide carbofuran.

Nanocolloidal gold particles were prepared and labeled to an anti-carbofuran monoclonal antibody (Mab). This conjugate was dispensed on the conjugated pad of a porous glass fiber. Ovalbumin (OVA)-carbofuran and goat anti-mouse IgG were dispensed on the nitrocellulose (NC) membrane and served as the test line and control line, respectively. The carbofuran-containing sample migrated to the NC membrane and reacted with the anti-carbofuran Mab labeled with the colloidal gold. The mixture diffused along the membrane and passed through the OVA-carbofuran in the test line via capillary action. The more analyte present in the sample, the more effectively it will compete with the carbofuran immobilized on the test line for binding to the limited amount of antibody labeled with colloidal gold. An adequate amount of carbofuran could prevent attachment of the colored conjugate to the test line. The presence or absence of a colored band on the test line could indicate a negative or positive result, respectively. When measured to the water sample spiked with carbofuran, this was obtained at or above 0.25 mg/L of carbofuran. The major advantages of the one-step strip test are that the detection time needed was <10 min and all of the reagents are included in the test device.

Antibodies, Monoclonal↗

PubMed2005

Filling carbon nanotubes with particles.

The filling of carbon nanotubes (CNTs) with fluorescent particles was studied experimentally and theoretically. The fluorescent signals emitted by the particles were visible through the walls of the nanotubes, and the particles inside the tubes were observable with an electron microscope. Taking advantage of the template-grown carbon nanotubes' transparency to fluorescent light, we measured the filling rate of the tubes with particles at room conditions. Liquids such as ethylene glycol, water, and ethylene glycol/water mixtures, laden with 50 nm diameter fluorescent particles, were brought into contact with 500 nm diameter CNTs. The liquid and the particles' transport were observed, respectively, with optical and fluorescence microscopy. The CNTs were filled controllably with particles by the complementary action of capillary forces and the evaporation of the liquid. The experimental results were compared and favorably agreed with theoretical predictions. This is the first report on fluorescence studies of particle transport in carbon nanotubes.

Capillary Action↗

PubMed1999

Evaluation of the HB-Quick: a portable hemoglobinometer.

OBJECTIVE: The Hb-Quick is a new portable hemoglobinometer that uses disposable cuvettes to measure the total hemoglobin concentration of capillary, venous, or arterial blood. Therefore, the objectives of this study were 1) to evaluate the performance of this compact, battery-powered hemoglobinometer by assessing its precision, accuracy, and linearity, 2) to determine whether its measurements suffer from interference by hemolysis, bilirubin, fetal hemoglobin, or hemodilution, and 3) to establish whether it can easily be used by clinical personnel with little or no laboratory training. METHODS: The precision of the test instrument was assessed by making repeated measurements on blood samples. Its accuracy and linearity were evaluated by comparing its measurements with the internationally accepted cyanmethemoglobin method. Samples of whole blood with and without bilirubin, fetal hemoglobin, hemolysis, and hemodilution were also analyzed to determine if any interference occurred when these disturbances were present, and it was placed in physicians' offices to evaluate its use by non-laboratory personnel. RESULTS: Repeated measurements on blood samples with a wide range of hemoglobin concentrations were consistent with the precision specification (0.25 g/dl). The bias of the new hemoglobinometer was calculated as the mean difference between its readings and measurements with the cyanmethemoglobin method, and its accuracy as the standard deviation of the differences between the two methods. As assessed in this manner, the new hemoglobinometer had a bias of -0.04 g/dl and an accuracy of 0.40 g/dl. The linearity was checked over a hemoglobin concentration range from 0 to nearly 30 g/dl. There was a highly significant linear relationship between its readings and measurements with the cyanmethemoglobin method (slope = 0.997, y-intercept = 0.005, r = 0.999). Complete hemolysis of the sample increased the readings on average by only 0.22 g/dl. Bilirubin (17.5 mg/dl) increased the reading by an average of 0.29 g/dl, and fetal hemoglobin (76.5% HbF) reduced the readings by an average of only 0.035 g/dl. Diluting blood samples with saline also did not appreciably affect its accuracy. CONCLUSIONS: The new hemoglobinometer is fast and easy to operate. No sample preparation or pipetting is required. To operate the instrument, the user simply allows a drop of blood to fill the disposable cuvette by capillary action and inserts the cuvette into the instrument. The instrument analyzes the 10 microl sample and displays the results in less than 10 seconds. The interference caused by hemolysis, hemodilution with saline, fetal hemoglobin, and bilirubin were too small to be of any dinical importance. Tests in physician's offices indicated that clinical personnel with little or no formal laboratory training could successfully use this device. The observed precision, accuracy, linearity, and freedom from interference indicate that this hemoglobinometer is suitable for near-patient testing in a wide range of clinical settings including physicians' offices.

Bilirubin↗

PubMed2001

Removal of hydrocarbons from wastewater using treated bark.

This paper explores the possibility of removing hydrocarbons (HCs) and trace elements from synthetic and industrial effluents using treated bark as biosorbent. Coniferous bark was treated either chemically (Tc) or biologically (Tb) to eliminate soluble organic compounds of bark. The removal efficiency (RE) of the HCs from a synthetic oil-water mixture containing spent diesel motor oil exceeds 95% using 2 g/L of treated bark mixed with a synthetic oil-water mixture containing 2 g/L of spent oil. Under these conditions, the retention capacity (RC) was approximately 1 g HC/g dry substrate. The sorption reaction seems to be quasi-instantaneous, and the retention capacity of spent oil on treated bark increases as the temperature augments. This implies that the retention mechanism is related to the capillary action. Results of Fourier transform infrared (FTIR) spectroscopy indicate that spent oil is mainly composed of alkanes. They also suggest that no chemical bonds between Tc and spent oil were established. Measurement of the surface tension of spent oil and the wetting index of the bark suggests that only spent oil will be retained by the substrate. Treatment of an industrial effluent containing 14.4 g/L of total HCs was performed using Tc. It was possible to remove 97% of HCs and retain some trace elements such as Al, Ca, Fe, Mg, S, and so on.

Biodegradation, Environmental↗

PubMed2005

Membrane-based wet electrostatic precipitation.

Emissions of fine particulate matter, PM2.5, in both primary and secondary form, are difficult to capture in typical dry electrostatic precipitators (ESPs). Wet (or water-based) ESPs are well suited for collection of acid aerosols and fine particulates because of greater corona power and virtually no re-entrainment. However, field disruptions because of spraying (misting) of water, formation of dry spots (channeling), and collector surface corrosion limit the applicability of current wet ESPs in the control of secondary PM2.5. Researchers at Ohio University have patented novel membrane collection surfaces to address these problems. Water-based cleaning in membrane collectors made of corrosion-resistant fibers is facilitated by capillary action between the fibers, maintaining an even distribution of water. This paper presents collection efficiency results of lab-scale and pilot-scale testing at FirstEnergy's Bruce Mansfield Plant for the membrane-based wet ESP. The data indicate that a membrane wet ESP was more effective at collecting fine particulates, acid aerosols, and oxidized mercury than the metal-plate wet ESP, even with approximately 15% less collecting area.

Air Movements↗

PubMed1992

Effect of drying period and soil moisture on egg hatch of the tadpole shrimp (Notostraca: Triopsidae).

Tadpole shrimp (Triops spp.) are potential biological control agents against larval mosquitoes in temporary ponds and flood-irrigated fields. In some rice field situations, however, they may become pests that uproot and eat young rice plants. In cursory observations, it has been reported that tadpole shrimp eggs do not readily hatch on flooding when the soil or substrate containing eggs is moist before flooding. The relationship between drying (moisture content) of soil and tadpole shrimp hatch was determined in studies conducted in mesocosms at the University of California Aquatic and Vector Control Research facilities at Riverside and at Oasis in the Coachella Valley of southern California. In laboratory hatching trials, an increase in hatch of Triops longicaudatus (LeConte) with declining soil moisture content was demonstrated (t = 8.4, P less than 0.001; r2 = 0.76). In field trials in mesocosms at Riverside, egg hatch increased with increased drying period and declining soil moisture content (G = 29.8, P less than 0.01). No hatch of eggs occurred after 3 d of drying, when soil moisture content was high, but a high level of hatching occurred after 7 and 14 d of drying, when soil moisture declined to low levels. At Oasis, soil moisture did not decrease with drying time because of porous soil and capillary action of water from adjacent flooded mesocosms and thick vegetation covering the pond bottoms. Therefore, hatch rates at Oasis were not associated with the length of the drying period (G = 35, P greater than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

In vitro alteration of Schirmer's tear strip wetting by commonly instilled anesthetic agents.

The Schirmer's tear test is often performed with topical anesthesia to reduce reflex tearing. Fluress (Barnes-Hind, Sunnyvale, CA, U.S.A.) and Fluoracaine (Akorn, Abita Springs, LA, U.S.A.) are commonly used anesthetic-fluorescein preparations that contain viscous additives. Because the rate of Schirmer's strip wetting is dependent on capillary action, a property related to solution viscosity and surface tension, spurious results may be obtained if these agents are used for anesthesia. We report in vitro Schirmer's strip wetting rates for various concentrations of Fluress and Fluoracaine, as well as pure fluorescein solution using a tear substitute (Dacriose; IOLAB, Claremont, CA, U.S.A.) as a diluent. Results showed a direct concentration-dependent reduction of Schirmer's strip wetting with time for both Fluress and Fluoracaine dilutions compared with Dacriose alone (p < 0.001) or Dacriose-fluorescein solutions (p < 0.001). In addition, Schirmer's wetting with Dacriose-fluorescein solutions caused a separation of the Dacriose and fluorescein wetting fronts (p < 0.001) but did not affect the overall Dacriose wetting. These data have clinical implications concerning false-positive results when testing for dry eyes.

Anesthetics, Local↗

PubMedDate not supplied

An in vitro model for studying the effect of the subcutaneous tunnel and the skin exit site on the accuracy of central venous catheter tip cultures.

The diagnosis of central venous catheter-related sepsis depends on a positive culture obtained from the distal intravascular portion of the catheter. The effects of the subcutaneous tunnel and the skin exit site on the accuracy of cultures obtained from the catheter are unknown. We have developed an in vitro model to study the effect of these variables. By inoculating polyethylene catheters embedded in agar with Pseudomonas aeruginosa, we were able to show that: (1) capillary action occurs along catheters in an agar tunnel, (2) organisms that are growing on the distal segment (tip) of the catheter can be dislodged from the surface of the catheter when it is pulled through the agar tunnel, and (3) pulling a catheter through a contaminated area results in distal contamination.

Agar↗

PubMed1993

Water Relation Alterations Observed during Hypersensitive Reaction Induced by Bacteria.

Upon exposure to pathogenic bacteria, resistant and nonhost plants undergo a hypersensitive reaction (HR) that is expressed as rapid plant cell death. If sufficient concentrations of these bacteria are inoculated to such plant tissue, then that portion of the tissue rapidly collapses and becomes necrotic. As the tissue collapses the water relations of inoculated tissues become markedly disturbed. We measured a decline in the relative water content (RWC) in the leaf-like cotyledons of cotton (Gossypium hirsutum cv Immune 216) within the first 4 h (cut at 1 h) after inoculation with Pseudomonas syringae pv tabaci. However, the decrease in RWC was not caused by a decrease in initial fresh weight but by increased water uptake during incubation in water. By 8 h after inoculation, cotyledons still on the plant had lost turgidity, and their area decreased. K+ efflux was also observed concurrently with the decrease in RWC, providing a reason for the loss of turgidity in the tissue. These observations suggest that cells lose turgor and change shape from cylinders with large intercellular spaces to those of a more tabular shape. During this change cell walls come closer together, providing an avenue for increased water uptake through capillary action. The stomatal diffusive resistance of intact cotyledons increased; hence, water loss through stomata is not the cause of the observed wilting and RWC decline. An increase in K+ per dry weight suggests that phloem loading or movement may also be impaired during bacterially induced HR.

Journal Article↗

PubMed1994

High-pressure freezing of cell suspensions in cellulose capillary tubes.

A procedure for efficient cryoimmobilization of large volumes of cell suspensions or micro-organisms by high-pressure freezing is described. This procedure uses transparent, porous cellulose capillary tubes with an inner diameter of 200 microns, into which the suspensions are drawn by capillary action. The tubes are processed by high-pressure freezing and freeze-substitution as if they were tissue samples. Centrifugation of suspensions at low temperatures is no longer necessary and cryopreparation is greatly facilitated. A very high yield of adequately frozen specimens is obtained due to the constant, defined sample geometry. This approach can also be used to process suspensions by conventional chemical fixation, eliminating the need to embed pellets in low-melting-point agarose, for example, prior to chemical fixation. The preparation procedure is demonstrated with suspensions of nematodes, paramecia and bacteria.

Animals↗

PubMed1969

Micromethod for assaying serum levels of erythromycin.

A micromethod for assaying serum levels of erythromycin is described. The assay had the following characteristics: detection of 0.03 to 0.035 mug/ml, a long-range curve which minimizes sample dilution, 0.04 ml for a single measurement (0.3 ml required for full coverage), and utility for a variety of body fluids. The method employs radial diffusion from small paper discs which were saturated by capillary action rather than by dipping or pipetting. Although the method was designed to handle serum in which the sample volume is limited, statistical analysis demonstrated that the method has satisfactory precision for routine use. A study of 10 consecutive assays indicates a precision of +/-12% at the 95% confidence limits. The method of least squares was used to calculate the line of best fit, and the statistics were developed on this basis. The assay method is applicable to a variety of antibiotics.

Anti-Bacterial Agents↗

PubMed1990

Comparative analysis of protein content in rat mesenteric tissue, peritoneal fluid, and plasma.

Albumin, transferrin, and total protein concentrations were measured in the mesenteric tissue, peritoneal fluid, and plasma of 12 ketamine-Nembutal-anesthetized Sprague-Dawley rats. Tissue samples were obtained with an 8-mm trephine; tissue water content was determined by a microgravimetric method to be 5.2 +/- 0.3 microgram water/microgram dry wt. Peritoneal fluid was collected by capillary action in hematocrit tubes, and blood samples were taken from a femoral artery catheter. Total protein concentrations of plasma (5.8 +/- 0.3 g/dl) and peritoneal fluid (2.6 +/- 0.1 g/dl) were determined by Lowry assay. Ratios of peritoneal fluid and tissue densitogram areas to plasma area were used to calculate total protein content of peritoneal fluid (2.5 +/- 0.1 g/dl) and tissue (1.8 +/- 0.2 g/dl). Albumin concentrations were 1.1 +/- 0.1 g/dl for tissue, 1.4 +/- 0.1 g/dl for peritoneal fluid, and 2.8 +/- 0.1 g/dl for plasma. Transferrin concentrations were 0.09 +/- 0.01 g/dl for tissue, 0.13 +/- 0.01 g/dl for peritoneal fluid, and 0.28 +/- 0.01 g/dl for plasma. Peritoneal fluid protein concentrations were similar to values found for lymph in previous studies. Protein concentration in the tissue buttons was significantly less than that of peritoneal fluid. This contradicts the widely held assumption that the protein concentration of fluid outside the matrix is representative of a well-mixed interstitial matrix fluid protein concentration.

Albumins↗

PubMedDate not supplied

VACUTEX: a dressing designed for patients, tailored by nurses.

VACUTEX is a new rapid capillary action dressing comprising three layers: two 100% polyester filament outer layers, and a 65% polyester and 35% cotton woven inner layer. The outer surfaces are fused in such a way as to prevent micro fibres shedding within the wound bed. No two wounds are alike, and wounds are often located in difficult-to-dress areas. This article will describe how VACUTEX, when used with creativity, addresses many of the challenges of wound management.

Aged↗

PubMed2004

Evaluation of a wound dressing using different research methods.

This article examines different methods of assessing wound progress in order to better inform future research designs and thus produce a more credible and valid bank of knowledge. Data collected in a study of Vacutex, a capillary action dressing, were reassessed using four different mechanisms: non-blind assessment by a research nurse; two different scoring systems based on wound size and appearance; and a blind randomized assessment using initial and final images of wounds.Non-blind assessment indicated that the Vacutex dressing was superior to standard dressings by +40.8% (P=0.022); assessment by wound area and overall appearance indicated +11.2% superiority (P is not significant); and the blind randomized image-based assessment indicated a +20.6% difference (P is not significant). Assessment by wound area and description did not allow a percentage superiority to be identified and the conclusion of this method was that there was no significant difference by rank sum testing. The different assessment techniques resulted in significantly different conclusions about the effectiveness of Vacutex. On balance, the blind, randomized, image-based assessment may miss some finer nuances of wound progress but is probably the most unbiased option because those assessing the wounds are not aware of which images are taken before or after wounds have been treated.

Bandages↗

PubMed1988

Effect of patient positioning on distribution of tetracycline in the pleural space during pleurodesis.

Thoracostomy tube drainage with tetracycline (TCN) instillation is an effective technique for management of recurrent, symptomatic, malignant pleural effusions. Although patient rotation through various positions after instillation of TCN has been advocated empirically, it has not been shown scientifically to be necessary and is often uncomfortable for the patient and time-consuming for personnel. Five patients with symptomatic, malignant pleural effusions were studied during pleurodesis using radiolabelled TCN. Scintigraphic imaging was done immediately after TCN instillation prior to patient rotation. Patients were rotated through six positions and multiple images were obtained at 30 and 120 minutes. Tetracycline dispersed throughout the pleural space within seconds. Patient positioning had no effect on the intrapleural distribution of TCN in four of the five patients. In one patient with loculated hydropneumothorax and trapped lung, rotation minimally improved distribution of TCN to the apex. Rotation during pleurodesis does not appear to be necessary in patients with a relatively normal pleural space. However, patient rotation enhances distribution of TCN when the lung is separated substantially from the chest wall, as with trapped lung. Possibly, in this situation the properties of fluid mechanics and capillary action no longer apply.

Adult↗