Plastic Capillaries Research Articles

Is the use of plastic capillary tubes justified for blood gases analysis?

Some clinical units, such as neonatal or maternity units, preferentially use capillary tubes when analysing blood gases. Using glass tubes is delicate and nurses must recollect blood when breaking. In order to eliminate this problem, we tested flexible, plastic capillary tubes in both the above mentionned units and in our biochemistry laboratory. Each unit, where glass tubes were habitually used, tested 200 flexible, plastic capillary tubes. In addition, the nursing staffed filled out a questionnaire concerned tube usage. Both units clearly preferred using the flexible tubes. In the laboratory, results for blood gas analyses were compared between rigid glass and flexible plastic capillary tubes for 112 patients. Concordance tests did not showed significant differences between the two tube types, except for hematocrit and total haemoglobin. A questionnaire was also presented to the lab technician, who confirmed the easier usability of plastic capillary tubes.

The separation of immiscible liquid slugs within plastic microchannels using a metallic hydrophilic sidestream

This paper describes experiments and related modelling on a new method for separating aqueous phase slugs from the surrounding organic matrix phase in segmented two phase flow in a plastic microcapillary film (MCF). Kerosene or paraffin oil was metered through a plastic capillary of 630 microns diameter and aqueous phase slugs were generated within the capillary by the continuous sidestream injection of water. It was found that the resulting aqueous phase slugs formed in the MCF could be subsequently easily separated from the organic phase by piercing the downstream sidewall of the plastic capillary with a hydrophilic metal hypodermic needle to draw off an aqueous sidestream. Optical scrutiny of the phase separation process indicated that two distinct disengagement mechanisms are involved, in which the metal needle tip either remains submerged in the aqueous phase or becomes periodically exposed to the organic phase at certain stages of the segregation process. The separation efficiency, i.e. the degree of residual phase cross-contamination, was determined as a function of both the sidestream needle angle and the depth of needle penetration into the capillary for a given flow rate and phase ratio. It was established that the separation efficiency was very sensitive to the downstream pressure balance between the organic mainstream flow in the plastic capillary and the aqueous sidestream flow through the needle. A mathematical model for the pressure balance conditions was developed by making certain simplifying assumptions and taking the Laplace interfacial pressure into account. The model predictions agreed surprisingly well with the experimental findings, thus providing circumstantial evidence for the validity of the insights into the phase separation mechanism.

Large size, high efficiency fiber-shaped dye-sensitized solar cells

A high-efficiency dye-sensitized solar cell prototype has been designed and fabricated, in which the working electrode and counter electrode are in direct contact and singly twisted. The cell is sealed in a capillary. In this solar cell configuration, the area ratio between the counter and working electrode is extremely low which allows the independent adjustment of electrolyte volume and the distance between counter electrode and photo-anode. Also it is more easily sealed compared to planar solar cell. The effects of TiO(2) film thickness, twisted pitch of counter electrode and length of device have been investigated. Our results indicate that this novel configuration has demonstrated excellent modularization function, three dimensional light harvesting capacities and the relative independence of incident light angles due to the symmetry structure. The power conversion efficiency of one cell of 9.5 cm in length can reach up to 5.41% at standard test condition (100 mW cm(-2)) and the power output may double under intense diffuse illumination. As far as we know, this is the longest and most efficient fiber-shaped dye-sensitized solar cell consisting of liquid electrolyte. The longer the fiber-shaped solar cell is, the more suitable it is for woven solar power textile if it is encapsulated in transparent flexible plastic capillary.

High‐throughput screening of chemical exchange saturation transfer MR contrast agents

A new high-throughput MRI method for screening chemical exchange saturation transfer (CEST) agents is demonstrated, allowing simultaneous testing of multiple samples with minimal attention to sample configuration and shimming of the main magnetic field (B(0)). This approach, which is applicable to diamagnetic, paramagnetic and liposome CEST agents, employs a set of inexpensive glass or plastic capillary tubes containing CEST agents put together in a cheap plastic tube holder, without the need for liquid between the tubes to reduce magnetic susceptibility effects. In this setup, a reference image of direct water saturation spectra is acquired in order to map the absolute water frequency for each volume element (voxel) in the sample image, followed by an image of saturation transfer spectra to determine the CEST properties. Even though the field over the total sample is very inhomogeneous due to air-tube interfaces, the shape of the direct saturation spectra is not affected, allowing removal of susceptibility shift effects from the CEST data by using the absolute water frequencies from the reference map. As a result, quantitative information such as the mean CEST intensity for each sample can be extracted for multiple CEST agents at once. As an initial application, we demonstrate rapid screening of a library of 16 polypeptides for their CEST properties, but in principle the number of tubes is limited only by the available signal-noise-ratio, field of view and gradient strength for imaging.

10.1007/s11452-008-2008-2

The evolution of the CAPEX facility and its basic diagnostics are described. The experiments carried out in the last modification of this facility accomplished with the demonstration of amplified spontaneous emission of neon-like argon (Ar8+) at the wavelength 46.88 nm. The first version of the facility, CAPEX1, operated with a plastic capillary and had a short high-power passive prepulse and an imperfect gas-filling system. In the second version, CAPEX2, a ceramic capillary was used, the prepulse amplitude was lowered, and the gas-filling system was improved. In the third, most successful version, CAPEX3, the capillary bending was reduced, a longer external prepulse was used, and the gas-filling system was further optimized. For each version, results of X-ray measurements are presented and interpreted.

Facilitating protein crystal cryoprotection in thick-walled plastic capillaries by high-pressure cryocooling.

Many steps in the X-ray crystallographic solution of protein structures have been automated. However, the harvesting and cryocooling of crystals still rely primarily on manual handling, frequently with consequent mechanical damage. An attractive alternative is to grow crystals directly inside robust plastic capillaries that may be cryocooled and mounted on the beamline goniometer. In this case, it is still desirable to devise a way to cryoprotect the crystals, which is difficult owing to the poor thermal conductivity of thick plastic capillary walls and the large thermal mass of the capillary and internal mother liquor. A method is described to circumvent these difficulties. It is shown that high-pressure cryocooling substantially reduced the minimal concentrations of cryoprotectants required to cryocool water inside capillaries without formation of ice crystals. The minimal concentrations of PEG 200, PEG 400 and glycerol necessary for complete vitrification under pressure cryocooling were determined.

Resolving crossing fibres using constrained spherical deconvolution: Validation using diffusion-weighted imaging phantom data

Diffusion-weighted imaging can potentially be used to infer the connectivity of the human brain in vivo using fibre-tracking techniques, and is therefore of great interest to neuroscientists and clinicians. A key requirement for fibre tracking is the accurate estimation of white matter fibre orientations within each imaging voxel. The diffusion tensor model, which is widely used for this purpose, has been shown to be inadequate in crossing fibre regions. A number of approaches have recently been proposed to address this issue, based on high angular resolution diffusion-weighted imaging (HARDI) data. In this study, an experimental model of crossing fibres, consisting of water-filled plastic capillaries, is used to thoroughly assess three such techniques: constrained spherical deconvolution (CSD), super-resolved CSD (super-CSD) and Q-ball imaging (QBI). HARDI data were acquired over a range of crossing angles and b-values, from which fibre orientations were computed using each technique. All techniques were capable of resolving the two fibre populations down to a crossing angle of 45°, and down to 30° for super-CSD. A bias was observed in the fibre orientations estimated by QBI for crossing angles other than 90°, consistent with previous simulation results. Finally, for a 45° crossing, the minimum b-value required to resolve the fibre orientations was 4000s/mm2 for QBI, 2000s/mm2 for CSD, and 1000s/mm2 for super-CSD. The quality of estimation of fibre orientations may profoundly affect fibre tracking attempts, and the results presented provide important additional information regarding performance characteristics of well-known methods.

Plastic Versus Glass Capillaries for Rapid-Cycle PCR

Rapid-cycle PCR uses fast temperature transitions and minimal denaturation and annealing times of "0" s to complete 30 cycles in 10 to 30 min. The most popular platform amplifies samples in glass capillaries arranged around a carousel with circulating air for temperature control. Recently, plastic capillary replacements for glass capillaries became available. We compared the performance of plastic and glass capillaries for rapid-cycle PCR. Heat transfer into plastic capillaries was slowed by thicker walls, lower thermal conductivity, and a lower surface area-to-volume ratio than glass capillaries. Whereas the denaturation and annealing target temperatures were reached by samples in glass capillaries, samples in plastic capillaries fell short of these target temperatures by 6 degrees -7 degrees C. Rapid-cycle PCR was performed on two human genomic targets (APOE and ACVRL1) and one plasmid (pBR322) to amplify fragments of 225-300 bp in length with melting temperatures of 90.3 degrees -93.1 degrees C. Real-time amplification data, end-point melting curves, and end-point gel analysis revealed strong, specific amplification of samples in glass and complete amplification failure in plastic. Only the APOE target was successfully amplified by extending the denaturation and annealing times to 5 or 10 s. A 20 s holding period was necessary to reach target temperatures in plastic capillaries.

Amplification of spontaneous emission of neon-like argon in a fast gas-filled capillary discharge

The evolution of the CAPEX facility and its basic diagnostics are described. The experiments carried out in the last modification of this facility accomplished with the demonstration of amplified spontaneous emission of neon-like argon (Ar8+) at the wavelength 46.88 nm. The first version of the facility, CAPEX1, operated with a plastic capillary and had a short high-power passive prepulse and an imperfect gas-filling system. In the second version, CAPEX2, a ceramic capillary was used, the prepulse amplitude was lowered, and the gas-filling system was improved. In the third, most successful version, CAPEX3, the capillary bending was reduced, a longer external prepulse was used, and the gas-filling system was further optimized. For each version, results of X-ray measurements are presented and interpreted.

Collaborative Study of a T-nos Real-Time PCR Method for Screening of Genetically Modified Organisms in Food Products

In the EU the presence of genetically modified organisms (GMO) in food is controlled by the Member States official laboratories within their national inspection and monitoring programs. The most frequently used approach to detect the presence of GMO material in different food matrices is the PCR-based screening for the CaMV 35S promoter and the nos terminator (T-nos) DNA sequence from Agrobacterium tumefaciens. A real-time PCR method for detection of T-nos and its validation in a collaborative trial study is described in this paper. The PCR system amplifies a 84 bp fragment and showed to be sensitive to detect at least 5 copies of the T-nos DNA sequence. The assay was adapted for use in real-time PCR instruments using plastic reaction vials and glass capillaries, respectively. A total of 24 laboratories participated in the study and each laboratory received 18 DNA blind samples prepared from GMO certified reference materials (0.1 % and 0.5 % NK601 maize) and from a non-GM maize flour. All samples containing NK603 maize DNA were correctly classified as T-nos positive by the participating laboratories. For the blank samples (0 % GMO) only three false-positive results were reported. A detailed evaluation of the results of the collaborative trial study is described.

CE‐ESI‐MS of biological anions in plastic capillaries at high pH

In this study, the potential of poly(methylmethacrylate) (PMMA, Plexiglas) and polyether ether ketone (PEEK) tubing for CE-ESI-MS separations of anions at high pH values was examined. A set of model compounds of biological interest was used to investigate the main operational parameters for CE-ESI-MS, such as the sheath-flow interface design, the polarity of the ionization voltage, the use of ammonia-based separation electrolytes, and the sheath liquid composition. Optimum separations and detection sensitivities in negative ESI mode were obtained using a running electrolyte of 75 mM of ammonia at pH 11 and a sheath liquid of 60:40 v/v or 75:25 v/v isopropanol/water with 0.5% v/v of ammonia. At these experimental conditions, PMMA and PEEK capillaries show good hydrolytic stabilities and lower EOF values than fused-silica columns. Better separation resolutions were obtained with PMMA capillary, but this plastic rapidly swelled and bled because of its limited chemical resistance to the sheath liquid. PMMA columns equipped with a fused-silica tip were used for a safer exposure to the sheath liquid, but the inner surface of the fused-silica tips had limited stability at pH 11. On the other hand, good separations and reproducibility on migration times and peak areas were obtained using PEEK capillaries without capillary column deterioration.

The Placenta

The human placenta is a discoid organ that has a hemochorial relationship with the mother. That is to say, the trophoblast that covers the villi is in direct contact with the maternal blood. Transfer of substances has to traverse the syncytiotrophoblast, cytotrophoblast, villous basement membrane, fetal capillary bed, and its endothelium. Although the placenta is the most available tissue, it is the least thoroughly investigated organ, and many aspects of its control still are unknown. Especially deficient is our knowledge of the genetic control of its many functions. The placenta also has a different imprinting pattern (paternal imprinting) from that of the embryo. The prevailing sentiment is that once delivery has occurred, it is a superfluous tissue that only needs to be discarded. There are many reasons, however, that knowledge of placental pathology can aid materially in a better understanding of newborns who have anomalies or neonatal problems. Further, a detailed examination of the placenta at birth can provide a better insight into prenatal life and its possible disturbances than is possible from notes in the history of the patient. The shape of the placenta is extremely variable (Fig. 1), probably due to placental location, its interaction with the endometrium, and uterine shape. The placenta implants anywhere in the uterus, but most commonly, it is in an anterior or posterior location. Much less often it is on the fundus. The shape often can be understood best by considering the history of its implantation. The reason for a specific shape can be derived further from the frequently aberrant shapes of twin placentas where competition for space in the uterus, a phenomenon that has been termed “trophotropism,” can be inferred to have existed. This term was used initially in attempts to explain the placental features in the uncommon event of a placenta …

Use of plastic capillaries for macromolecular crystallization

Techniques of crystallization of biomolecules in plastic fluorocarbon-formulated capillaries (Nalgene 870 PFA tubing) are presented. These crystallization methods employ batch, free-interface liquid–liquid diffusion alone, or a combination with vapor diffusion. The growth of crystals of test proteins such as thaumatin and glucose isomerase, as well as of proteins studied in the laboratory, such as dihydrolipoamide dehydrogenase, has been demonstrated. Once the solutions were loaded in capillaries, they were stored in the tubes in frozen state at cryogenic temperatures until required for crystallization experiments.

Use of fluoride oxalate tubes to monitor the accuracy of home capillary glucose measurements during pregnancy

AbstractTight control of glycaemia during gestation is the mainstay of antenatal care in women with diabetes. This relies heavily on blood glucose monitoring. A simple technique for assessing the accuracy of the patients' own blood glucose monitoring is described. The method involves patients collecting a few drops of blood in fluoride oxalate‐coated plastic capillary tubes, which they store in their own refrigerator before delivery for laboratory analysis on the day of the antenatal clinic assessment. The readings can be compared with blood glucose monitor readings recorded by the patient and subsequently used by clinicians and nurses to guide therapy. Copyright © 2003 John Wiley & Sons, Ltd.

Simultaneous determination of pesticides using a four-band disposable optical capillary immunosensor.

The development of a four-band capillary optical immunosensor for the simultaneous determination of mesotrione, hexaconazole, paraquat, and diquat is described. Four distinct bands (each corresponding to a different analyte) are created in the internal walls of a plastic capillary by immobilizing protein conjugates of the analytes. To perform the assay, the capillary is filled with a mixture of anti-analyte-specific antibodies together with a standard or sample containing the analyte(s). After a short incubation, a mixture of the appropriate second antibodies labeled with fluorescein is introduced into the capillary. To measure the fluorescence intensity bound onto each band, the capillary was scanned, perpendicularly to its axis, by a laser light beam. Part of the emitted photons were trapped into the capillary walls and waveguided to a photomultiplier placed at the one end of the capillary. The analytical characteristics of the assays of mesotrione, paraquat, diquat, and hexaconazole were as follows: detection limits of 0.04, 0.06, 0.09, and 0.10 ng/mL, respectively; dynamic ranges up to 9, 6, 12, and 15 ng/ mL, respectively, intra- and interassay CVs less than 10%. The analytical characteristics of the assays were comparable with those of the corresponding single-analyte fluoroimmunoassays performed in microtitration wells, proving the ability of the proposed immunosensor for reliable multianalyte determinations. Moreover, the combination of low-cost disposable plastic capillary tubes with the low consumption of reagents, the short assay time, and the multianalyte feature of the proposed immunosensor indicates its potential for environmental analysis.

Use of Capillaries for Macromolecular Crystallization in a Cryogenic Dewar

The enhanced gaseous nitrogen (EGN) dewar is a cryogenic dry shipper with a sealed cylinder inserted inside along with a temperature-monitoring device, and is intended for macromolecular crystallization experiments on the International Space Station. Within the dewar, each crystallization experiment is contained as a solution within a plastic capillary tube. The standard procedure for loading samples in these tubes has involved rapid freezing of the precipitant and biomolecular solution, e.g., protein, directly in liquid nitrogen; this method, however, often resulted in uncontrolled formation of air voids. These air pockets, or bubbles, can lead to irreproducible crystallization results. A novel protocol has been developed to prevent formation of bubbles, and this has been tested in the laboratory as well as aboard the International Space Station during a 42-day long mission of July/August 2001. The gain or loss of mass from solutions within the plastic capillaries revealed that mass transport occurred among separated tubes, and that this mass transport was dependent upon the hygroscopic character of the solution contained in any given tube. The surface area of the plastic capillary tube also related to the observed mass transport. Furthermore, the decreased mass of solutions of protein correlated to observed formation of protein crystals.

Multi-analyte capillary immunosensor for the determination of hormones in human serum samples

In this work we present the development of a multi-analyte immunosensor for the determination of follitropin, human chorionic gonadotropin and prolactin in human serum. The immunosensor is based on plastic capillaries. According to the methodology, discrete areas of the internal capillary surface are coated with different antibodies, which are highly specific for each one of the analytes to be determined. The sample that will be analyzed along with a mixture of analyte-specific biotinylated antibodies is introduced into the capillary. The coated and the detection antibodies react with different epitopes of the analytes in the sample to form a ‘sandwich’. The detection is based on reaction of the immobilized biotinylated antibody with streptavidin labeled with R-phycoerythrin. The fluorescent areas formed were quantified by scanning the capillary with a light beam of appropriate wavelength. A light sensor placed at the end of the capillary detects the emitted photons, that are trapped and waveguided into the capillary walls. The multi-analyte immunosensor assays were characterized by high specificity and short analysis time. In addition, the results obtained by the multi-analyte optical capillary immunosensor were comparable to those obtained by immunofluorimetric assays performed in microtitration wells. Potential applications of the proposed immunosensor include determination of several analyte panels in a broad spectrum of disciplines such as endocrinology, hematology, and oncology.

Fabrication of a capillary immunosensor in polymethyl methacrylate

A method for fabricating capillary-based immunosensors in a coupon milled from an inexpensive, commodity plastic (PMMA, plexiglass) is demonstrated. The key feature of the technique is the use of sol–gel technology to deposit a glass-like (SiOH) film on surfaces of the plastic capillary channels to facilitate antibody immobilization. The utility of this method was demonstrated in the context of continuous flow displacement immunosensors for the explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). These sensors exhibited sensitivity to low μg/l RDX concentrations and peak-to-peak signal variations that were generally less than 10% for multiple injections at a single RDX concentration. The useful lifetime of the coupons in these experiments was greater than 10 h even after multiple exposures to high (1000 μg/l) RDX levels. This sensor platform has the physical characteristics needed for a portable field instrument: small, light-weight, and rugged.

Separation of porphyrins by capillary electrophoresis in fused-silica and ethylene vinyl acetate copolymer capillaries with visible absorbance detection.

A mixture of 5 porphyrins were separated by capillary electrophoresis. A UV-VIS detector was used to detect the separated components. Separation was performed in 2 types of capillaries, i.e. fused-silica and ethylene vinyl acetate copolymer (EVA) plastic capillaries. The concentration limit of detection (CLOD), mass limit of detection (MLOD), and relative standard deviations (RSD) of migration time and area were investigated. LOD was comparable to that of epi-fluorescence detection. LOD was lower when separation was performed in EVA capillary compared to fused-silica capillary. RSD of migration times of the porphyrins when separated in fused-silica capillary ranges between 0.5 to 1.6% and in EVA capillary ranges between 0.3 to 1.2%. Area RSD in fused-silica capillary ranges between 7 to 20% and in EVA capillary ranges between 4.7 to 12.3%. Urine spiked with porphyrins was also analysed by CE using fused-silica and EVA capillaries. Analysis of urine sample spiked with porphyrins showed that stacking effect of porphyrins was observable only in fused-silica and not in EVA capillary. This led to similar LOD in fused-silica capillary to those for EVA capillary.

Determination of the isoelectric point of the capillary wall in capillary electrophoresis: Application to plastic capillaries

A refined method for measuring endoosmotic flow in capillaries based on weighing the amount of liquid transferred is described. The method has been applied to the estimation of isoelectric points of two types of plastic capillaries (polytetrafluoroethylene and polytetrafluoroethylene—polyhexafluoropropylene copolymer). Contrary to expectation both plastic capillaries exhibited considerable electroosmotic flow and changes in hydrodynamic flow resistance without applied voltage. The nature of these phenomena is discussed.