Biomedical subjects

Gilles Marchand

Publications and source records attributed to Gilles Marchand.

3 recordsLinked to original sources

PubMed2006

Ionic liquid droplet as e-microreactor.

A powerful approach combining a droplet-based, open digital microfluidic lab-on-a-chip using task-specific ionic liquids as soluble supports to perform solution-phase synthesis is reported as a new tool for chemical applications. The negligible volatility of ionic liquids enables their use as stable droplet reactors on a chip surface under air. The concept was validated with different ionic liquids and with a multicomponent reaction. Indeed, we showed that different ionic liquids can be moved by electrowetting on dielectric (EWOD), and their displacement was compared with aqueous solutions. Furthermore, we showed that mixing ionic liquids droplets, each containing a different reagent, in "open" systems is an efficient way of carrying supported organic synthesis. This was applied to Grieco's tetrahydroquinolines synthesis with different reagents. Analysis of the final product was performed off-line and on-line, and the results were compared with those obtained in a conventional reaction flask. This technology opens the way to easy synthesis of minute amounts of compounds ad libitum without the use of complex, expensive, and bulky robots and allows complete automation of the process for embedded chemistry in a portable device. It offers several advantages, including simplicity of use, flexibility, and scalability, and appears to be complementary to conventional microfluidic lab-on-a-chip devices usually based on continuous-flow in microchannels.

Ions↗

PubMed2005

Electrical detection of DNA hybridization based on enzymatic accumulation confined in nanodroplets.

Electrical monitoring of DNA hybridization is one way to reduce the cost and size of the DNA chip reader in comparison with the more classical optical detection. Within electrical methods, electrochemical detection shows very high performances in terms of accuracy and sensitivity, especially when an enzymatic accumulation is used to amplify the signal. However, signal multiplexing for miniaturized systems based on both enzymatic accumulation and electrochemical detection remains challenging due to the Brownian diffusion of the detected product of the enzymatic reaction. We present here a DNA chip with electrical detection based on the following sequence: (i) hybridization of nucleic acids and washing in a liquid layer as usual, (ii) formation of independent nanodroplets on each detection site, (iii) enzymatic accumulation in each droplet avoiding cross-contamination between neighboring sites, and (iv) electrochemical detection of the product accumulated during the enzymatic reaction. The simple and fast transition from the liquid layer (hybridization step) to an array of nanodroplets (enzymatic accumulation and detection steps) was performed through the filling of the hybridization chamber with a solution containing the enzymatic substrates, the drawing of this solution, and the simultaneous creation of droplets thanks to retention areas based on circular rims or hydrophilic rings. Using this approach, hybridization is achieved in a liquid layer as usual, followed by the enzymatic accumulation in nanodroplets to avoid the cross-talk between neighboring sites. Moreover, working in droplets enables a fast increase in the concentration of the product generated by the enzymatic reaction and thus an improvement of the detection limit of the system.

Base Pairing↗

PubMed2005

Opto-electronic DNA chip: high performance chip reading with an all-electric interface.

Reading of DNA chips is usually based on fluorescence labeling of hybridised target molecules. Combined with the use of confocal fluorescence scanners, this approach shows very high performances in terms of accuracy and sensitivity. However, fluorescence readers remain costly and cumbersome. This prevents the use of DNA chips as a decentralised testing tool. Electrical monitoring of hybridisation is one way to reduce the cost and size of the reader. However, the multiplexing of electric detection-based systems in a miniaturised form remains challenging. Here, we present a system based on the use of a low cost CMOS photodetector array as a solid support for a DNA chip, coupled with revelation by enzyme-catalysed chemiluminescence. This system is shown to allow the detection of low pM target concentrations with a 3 logs dynamic range on dense DNA microarrays, with excellent inter-spot reproducibility. Combining electric interface and high analytical performances, this opto-electronic DNA chip is one attractive solution for nucleic acids detection and analysis in disposable, fully automatised, total analysis systems developed for decentralised testing.

Biosensing Techniques↗