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ABSTRACT: To progress in basic science and drug development, convenient methodology for detecting specific biological molecules and their interaction in living organism is in high demand. After more than 20 years of increasing research efforts, micro and nanotechnologies are now mature to propose a new class of miniature devices and principles enabling compartmentalized bioassays. Among them, this review proposes various examples that include array of electro-active microwells for highly parallel single cell analysis, cost-effective nanofluidic for DNA separation, parallel enzymatic reaction in 100pL droplet and high-throughput platform for membrane proteins assays. The micro devices are presented with relevant experiments to foresee their future contribution to translational research and drug discovery.
Drug discovery today 02/2013; · 6.63 Impact Factor
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ABSTRACT: Droplet generation and transportation for biological reactions are conducted with liquid dielectrophoresis (LDEP), forming two hundred picoliter droplets and aligning them in an open environment above the micro-machined electrodes. The generation of the dielectrophoresis signals was critically examined to actuate droplets in biological solutions without excessive Joule heating. Enzymatic reactions between β-galactosidase and fluorescein di-β-D-galactopyranoside were succeeded in manipulated droplets, which was confirmed by fluorescence imaging. These results allow us to propose the integration of LDEP actuation in high throughput biomolecular assays.
ChemPhysChem 07/2012; 13(14):3308-12. · 3.41 Impact Factor
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ABSTRACT: DNA manipulation based on dielectrophoresis between microfabricated electrodes is one of the most efficient methods for the physical handling of molecules. Dielectrophoresis is routinely used for stretching and trapping DNA molecules between the opposing tips of silicon nanotweezers. However, the precise number of trapped molecules is difficult to predict, as a continuous application of ac voltage continually attracts the molecules while the electric-field-induced fluid flow prevents them from bridging the tips. To circumvent this difficulty, the dielectrophoresis signal is applied during very short intervals. In this pulsed mode, the electrohydrodynamic fluid flow is lessened and the molecule trapping success rate is greatly enhanced. A fluorescently labeled single λ-DNA molecule was successfully stretched and captured by the silicon nanotweezers with 50 ms pulses of a 1 MHz, 1 MV m−1 ac dielectrophoresis voltage. This single-molecule trapping between the tweezers' tips is monitored, in real time, under fluorescence imaging.
Journal of Micromechanics and Microengineering 04/2011; 21(5):054020. · 2.11 Impact Factor
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Micromachines. 01/2011; 2:258-273.
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BIODEVICES 2009 - Proceedings of the International Conference on Biomedical Electronics and Devices, Porto, Portugal, January 14-17, 2009; 01/2009
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ABSTRACT: Applications of microelectromechanical systems (MEMS) technology are widespread in both industrial and research fields providing miniaturized smart tools. In this review, we focus on MEMS applications aiming at manipulations and characterization of biomaterials at the single molecule level. Four topics are discussed in detail to show the advantages and impact of MEMS tools for biomolecular manipulations. They include the microthermodevice for rapid temperature alternation in real-time microscopic observation, a microchannel with microelectrodes for isolating and immobilizing a DNA molecule, and microtweezers to manipulate a bundle of DNA molecules directly for analyzing its conductivity. The feasibilities of each device have been shown by conducting specific biological experiments. Therefore, the development of MEMS devices for single molecule analysis holds promise to overcome the disadvantages of the conventional technique for biological experiments and acts as a powerful strategy in molecular biology.
Analytical and Bioanalytical Chemistry 04/2008; 391(7):2385-93. · 3.78 Impact Factor
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ABSTRACT: The study of the electrical properties of DNA has aroused increasing interest since the last decade. So far, controversial arguments have been put forward to explain the electrical charge transport through DNA. Our experiments on DNA bundles manipulated with silicon-based actuated tweezers demonstrate undoubtedly that humidity is the main factor affecting the electrical conduction in DNA. We explain the quasi-Ohmic behavior of DNA and the exponential dependence of its conductivity with relative humidity from the adsorption of water on the DNA backbone. We propose a quantitative model that is consistent with previous studies on DNA and other materials, like porous silicon, subjected to different humidity conditions.
Biophysical Journal 02/2008; 94(1):63-70. · 3.65 Impact Factor
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ABSTRACT: This paper presents a systematic method to isolate and trap long single DNA segments between integrated electrodes in a microfluidic environment. Double stranded lambda-DNA molecules are introduced in a microchip and are isolated by electrophoretic force through microfluidic channels. Downstream, each individual molecule is extended and oriented by ac dielectrophoresis (900 kHz, 1 MV m(-1)) and anchored between aluminium electrodes. With a proper design, a long DNA segment (up to 10 microm) can be instantly captured in stretched conformation, opening way for further assays.
ChemPhysChem 09/2007; 8(12):1875-80. · 3.41 Impact Factor
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ABSTRACT: The analytical method of determining enzyme activity by liquid chromatography-mass spectrometry (LC/MS) was developed and applied for investigation of the effect of polycyclic aromatic hydrocarbons (PAHs) on the enzyme activity of chitinase. The measurement of chitinase activity by LC/MS is useful in order to use the nonderivatized substrate, which can show in vivo chitinase activity. Substrate consumption and product formation were monitored in order to determine chitinase activity. It was shown that, for the first time, in vitro addition of PAHs inhibited the activity of chitinase in a noncompetitive manner. The IC(50) value of benzo[a]pyrene was 1.4 microM, and PAHs containing four or more aromatic rings showed the same or higher inhibitory effect, whereas PAHs with a lower number of aromatic rings showed lower inhibition of the chitinase activity than benzo[a]pyrene.
Analytical and Bioanalytical Chemistry 05/2007; 387(8):2641-4. · 3.78 Impact Factor
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ABSTRACT: A microchip-based method was developed for on-line determination of trace sulfur dioxide (SO(2)) in air. Gaseous SO(2), which diffused through the porous glass materials on the microchip, was absorbed into an absorption solution of triethanolamine (TEA) as sulfite ions and reacted with N-(9-acridinyl)maleimide (NAM), which was used as a fluorescent reagent. The fluorescence of NAM-sulfite in micro-fluidic channel was detected. The calibration curve of sulfite ions in the range of 1.5-30mumol/L (SO(2) 3-60ppbv) showed a linear relation R(2)=0.995, and the relative standard deviation (R.S.D.) was 1.9% for 10mumol/L sulfite ions in five measurements. The entire measurement procedure was achieved by the integrated microchip, and the consumption of reagents was drastically reduced. It was satisfactory to apply this method to determine on-line the SO(2) level in the air.
Talanta 10/2005; 67(3):646-50. · 3.79 Impact Factor
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ABSTRACT: A laser-induced fluorescence microscopic system based on optical parametric oscillation has been constructed as a tunable detector for microchip analysis. The detection limit of sulforhodamine B (Ex. 520 nm, Em. 570 nm) was 0.2 mumol, which was approximately eight orders of magnitude better than with a conventional fluorophotometer. The system was applied to the determination of fluorescence-labeled DNA (Ex. 494 nm, Em. 519 nm) in a microchannel and the detection limit reached a single molecule. These results showed the feasibility of this system as a highly sensitive and tunable fluorescence detector for microchip analysis.
Analytical and Bioanalytical Chemistry 07/2005; 382(4):992-5. · 3.78 Impact Factor
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ABSTRACT: A new NO(2) measurement collection device developed in this study indicates efficient absorption, enough to be applied to the practical determination of atmospheric NO(2), which should become a useful tool compared with conventional methods.
The Analyst 03/2004; 129(2):105-6. · 4.23 Impact Factor
