Dynamic single-cell analysis is a very important and frontier research field of single-cell analysis. Microfluidic techniques
have become new and effective tools for precise, high-throughput, automatic analysis of single-cell dynamic process. This
review aims to give an overview of dynamic single-cell analysis methods based on microfluidic platforms, with emphasis on
the recent developments of microfluidic devices and its application to real-time dynamic monitoring of the signal molecules
release from single living cell with temporal and spatial resolution, dynamic gene expression in single cells, the cell death
dynamic events at the level of a single cell, and direct cell—cell communication between individual cell pairs.
[Show abstract][Hide abstract] ABSTRACT: A general procedure is presented for the fabrication of miniaturized continuous flow analytical microsystems based on photometric
detection using the low temperature co-fired ceramics technology. Optical elements such as light emitting diodes and photodiodes
(all in the size of a few hundred micrometers) are integrated by means of an off-chip approach. A simple procedure is demonstrated
to integrate a glass window after the ceramic sintering in order to minimize the decrease in sensitivity due to the reduction
of the optical path length when scaling down. A flow cell with a shape of a bubble has been used to increase the area of the
light beam. The device is robust, affordable, and small-sized. It enables absorbance measurements to be performed in-situ
or for continuous monitoring of environmental samples. Specifically, a microsystem is introduced for colorimetric determination
of chromium (VI) ion in waters based on the diphenylcarbazide reagent as a model. Under the optimized conditions, a linear
response is obtained for the concentration range from 0.1 to 20mgL−1, with a detection limit of 50μgL−1.
KeywordsLow-temperature co-fired ceramics–Microanalyzer–Photometric detection–Chromium (VI)–Diphenylcarbazide
[Show abstract][Hide abstract] ABSTRACT: The immobilization of acetylcholinesterase on platinum microelectrodes modified with p-nitrobenzenediazonium is optimized. In the first step, a layer of p-nitrophenyl groups was deposited on the surface and then reduced to p-aminophenyl groups. Finally, the enzyme was linked to the amino groups on the surface using glutaraldehyde. Each step of the electrode modification was characterized by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) at acidic and neutral pH to modify the electric charges of different bound moieties. The deposition of diazonium groups was attempted by potentiometry, amperometry or CV, but only potentiometry proceeded without passivation of the surface. The use of microelectrodes improved the limit of detection of ethylparaoxon measurements to 20 nM (compared to 100 nM in case of screen-printed electrodes based on the same method of immobilization). The method allowed the production of stable and reproducible amperometric microbiosensors and may be adapted to other enzymes and electrode materials.
[Show abstract][Hide abstract] ABSTRACT: The ability to perform a fluorescence-based quantitative determination of a biologically important analyte directly released from mammalian cells using a standard microtiter plate reader to measure wells integrated into a microfluidic device is reported. Specifically, the amount of nitric oxide (NO) released from flowing erythrocytes (ERYs) exposed to a hypoxic buffer is measured using a fluorescein-based probe. The ERYs are pumped through channels in one layer of the poly(dimethylsiloxane) (PDMS) device; as these cells release NO, it flows through a porous polycarbonate membrane to the probe. The device is then placed into a standard microtiter plate reader for measurement, with the entire calibration and analyte determination occurring simultaneously. Using this method, NO release from hypoxic ERYs was determined to be 6.9 +/- 1.8 microM, a significantly increased value in comparison to that from normoxic ERYs of 0.60 +/- 0.04 microM (p < 0.001, n = 4 rabbits). Furthermore, the reproducibility (reported as a %RSD) of measuring fluorescence standards was 3.5%. Detection limits, dynamic range, and optimal membrane pore diameters are also reported. This device enables the use of a standard high-throughput tool (the plate reader) to measure analytes in a microfluidic device, the ability to improve the quantitative determination of a relatively unstable molecule (NO), and the incorporation of a flow component and blood constituent into a system that can be combined with microtiter plate technology.
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