Laser-induced Fluorescence Detection Technique Research Articles

Size-resolved counting of circulating tumor cells on pinched flow-based microfluidic cytometry.

Precise cell detecting and counting is meaningful in circulating tumor cells (CTCs) analysis. In this work, a simple cyclic olefin copolymer (COC) microflow cytometer device was developed for size-resolved CTCs counting. The proposed device is constructed by a counting channel and a pinched injection unit having three channels. Through injection flow rate control, microspheres/cells can be focused into the centerline of the counting channel. Polystyrene microspheres of 3, 9, 15, and 20µm were used for the microspheres focusing characterization. After coupling to laser-induced fluorescence detection technique, the proposed device was used for polystyrene microspheres counting and sizing. A count accuracy up to 97.6% was obtained for microspheres. Moreover, the proposed microflow cytometer was applied to CTCs detecting and counting. To mimic blood sample containing CTCs and CTCs mixture with different subtypes, an MDA-MB-231 (human breast cell line) spiked red blood cells sample and a mixture of MDA-MB-231 and MCF-7 (human breast cell line) sample were prepared, respectively, and then analyzed by the developed pinched flow-based microfluidic cytometry. The simple fabricated and easy operating COC microflow cytometer exhibits the potential in the point-of-care clinical application.

Real-Time Continuous Identification of Greenhouse Plant Pathogens Based on Recyclable Microfluidic Bioassay System.

The development of a real-time continuous analytical platform for the pathogen detection is of great scientific importance for achieving better disease control and prevention. In this work, we report a rapid and recyclable microfluidic bioassay system constructed from oligonucleotide arrays for selective and sensitive continuous identification of DNA targets of fungal pathogens. We employ the thermal denaturation method to effectively regenerate the oligonucleotide arrays for multiple sample detection, which could considerably reduce the screening effort and costs. The combination of thermal denaturation and laser-induced fluorescence detection technique enables real-time continuous identification of multiple samples (<10 min per sample). As a proof of concept, we have demonstrated that two DNA targets of fungal pathogens (Botrytis cinerea and Didymella bryoniae) can be sequentially analyzed using our rapid microfluidic bioassay system, which provides a new paradigm in the design of microfluidic bioassay system and will be valuable for chemical and biomedical analysis.

Rapid Determination of Vitamin B2 in Foods by HPLC with in Capillary Optical Fiber Laser-Induced Fluorescence Detection Technique

Rapid Determination of Vitamin B2 in Foods by HPLC with in Capillary Optical Fiber Laser-Induced Fluorescence Detection Technique

Note: A laser-flash photolysis and laser-induced fluorescence detection technique for measuring total HO2 reactivity in ambient air

A novel instrument for measuring total HO2 reactivity in the troposphere was successfully developed using a laser-flash photolysis and laser-induced fluorescence detection technique. Validation and testing were conducted through kinetic measurements of the reaction of HO2 radicals with NO2, and the results were found to be in good agreement with recent recommended values. The limit of detection (LOD) for HO2 loss rate measurement is achieved to be 0.024 s(-1) (3σ) with 60 times decay integrations. An observation of ambient air was carried out in a suburb of Tokyo to test the practical use of the developed instrument and un-expected rapid HO2 loss rate has been observed.

Analysis of trace amino acid neurotransmitters in hypothalamus of rats after exhausting exercise using microdialysis

A simple but effective coupling of microdialysis and capillary electrophoresis with laser induced fluorescence detection technique was applied to analysis of amino acid neurotransmitters in the hypothalamus of rats after acute exhausting exercise. The separation of amino acids was achieved using an uncoated fused-silica capillary (57 cm×75 μm I.D.) with a buffer of 10 m M disodium tetraborate at pH 10 and an applied voltage of 12.5 kV. The detection limit was 10 −10 M for each amino acid. It is sufficiently sensitive and rapid for the determination of amino acids in a 5-μl Microdialysate. In comparison to pre-exercise, a significant increase in the levels of six hypothalamic amino acids (arginine, glycine, lysine, glutamic acid, alanine, γ-amino- n-butyric acid) was found after exercise. These results demonstrate that the increase of metabolic amino acids in the hypothalamus of rats can be induced by exhausting exercise and suggests that amino acid neurotransmitters may play functional roles in the central effects of exercise.

Laser-induced fluorescence detection of malignant gliomas using fluorescein-labeled serum albumin: Experimental and preliminary clinical results

To delineate the tumor margins of malignant gliomas laser-induced fluorescence detection technique was applied using 5-aminofluoresceln-albumin as the fluorescent dye. The 5-aminofluorescein was linked to serum albumin (= AFlc-SA) as a cumulative protein label using residualizing markers. In a C6-glioma model the biodistribution and pharmacokinetics of the injected dye were investigated by labeling the protein conjugate with 111 In-DTPA. Twenty-four hours after Intravenous Injection of the dye, fluorescence was activated by an argon laser and inspected in the C6-gliomas. Histological examinations were performed to compare the microscopic margins of the fluorescence-stained tumors with hematoxylin/eosin. The tumor uptake 24 h after dye injection was 23-fold higher than in the surrounding brain. Fluorescence inspection under laser activation demonstrated clearly stained and sharply demarcated tumors. The microscopic borders of the tumors corresponded exactly with the fluorescence, also demonstrating intracellular tumor uptake of the dye. In a preliminary study, three patients with malignant gliomas were operated using laser-induced fluorescence detection technique after injection of AFlc-SA. In all patients, the borders of the malignant gliomas were clearly stained by AFlc-SA during surgery. Laser-induced fluorescence imaging using the albumin conjugate AFlc-SA may be a promising method for delineating tumor margins which are hard to detect under the operating microscope alone. [Neurol Res 2000; 22: 481-489]

Kinetic study of the reactions of cyanyl radical with oxygen and carbon dioxide from 292 to 1500 K using high-temperature photochemistry

Absolute rate constants for the reaction of CN with O{sub 2} have been measured as a function of temperature (292-1,565 K) and pressure (5-80 Torr), by combining the laser-induced fluorescence detection technique with high-temperature reactor technology. CN radicals were generated by using 193-nm excimer laser photolysis of dilute C{sub 2}N{sub 2}/Ar mixtures. Decays of the radical concentration were monitored by using laser-induced fluorescence (LIF) near 387 nm under pseudo-first-order conditions. The reaction of CN with O{sub 2} has a negative temperature dependence and is independent of pressure. These data contain minimal curvature and are adequately fit by the expression k ({plus minus}2{sigma}) = (1.02 {plus minus} 0.12) {times} 10{sup {minus}11} exp((+220 {plus minus} 25)/T) cm{sup 3}/(molecule s). This result represents the widest continuous temperature range over which this rate constant has been measured to date. For the reaction with CO{sub 2}, the Cn decays are complex and are strongly dependent on the gas temperature. No detectable reaction is observed for temperatures below 900 K. For temperatures above about 1150 K, CN decays are biexponential. Because of the complexities in the behavior of the data, no reliable Arrhenius rate parameters were determined.

Laser-induced fluorescence study of the F + I2→ IF + I reaction

The F + I2→ IF + I reaction has been studied in a crossed-beam experiment. The IF rovibrational distribution has been measured with the laser-induced fluorescence detection technique. Many new and important results concerning the energy disposal in this reaction are thus obtained. Moreover, a bimodal rotational distribution is observed in several vibrational levels: this phenomenon seems to be due to migratory collisions.