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A Lab-on-a-CHIP

Biosensors and biochips are progressing by leaps and bounds, and feature among the most exciting new approaches in nanobiotechnology. Biosensors, though still at the prototype stage, “are used to detect a particular 'biological species' (such as DNA, proteins, viruses, etc.), for instance in a highly complex system like a drop of blood,” explains Anne-Marie Gué, of LAAS.1

lab on a ship

© E. Perrin/LAAS/CNRS Photothèque

Nanomanufacturing technologies are used to develop tools for biology or medicine, like the biochips shown here.



“The possibilities opened up by nanotechnology are far-reaching. For example, scientists can use 'probes'—DNA strands, or antibodies—grafted on silicon nanowires or nanobeams to catch specific molecules.” When the target binds to an ultra-sensitive microbeam, the beam starts to vibrate, showing that the target molecule has been captured, while the rest of the system analyzes it. “At the Institute for Fundamental Electronics (IEF),2 we are developing a novel nano-biosensor. Each beam has an internal channel etched into it along which biological fluid can circulate. So the beam itself is not immersed in the fluid,” explains Jean-Michel Lourtioz. “This trick makes it easier to detect variations in the amplitude or in the frequency of vibration.”
And then there are biochips, already used by some medical laboratories. Rather than identifying a single molecule in a biological sample, “the objective here is to carry out a large number of analyses at the same time,” says Gué.
To do this, the biochips are made up of a solid substrate (glass, plastic, or silicon) covered with a microarray of tiny sites on which are placed molecules of DNA, proteins, or chemical groups that can specifically capture complementary DNA or RNA (DNA chips), or proteins (protein chips). “A DNA chip is able to simultaneously analyze anywhere between dozens and thousands of different DNA sequences to identify a virus or detect a specific marker for a disease.” Unlike biosensors, signal readout is not incorporated into the biochip, but carried out by external instruments. “One promising development, where both technologies would meet, is the integration of nanobio-sensors at each site of a biochip,” adds Gué. But the real challenge is to integrate complete analytical procedures on very small surface areas. Biosensors and biochips could thus become a “lab-on-a-chip” (LOC). In such a device, it would even be possible to integrate lasers, made from semi-conducting nanostructures of the gallium nitride (GaN) and zinc oxide (ZnO) families, which are very much in fashion at CRHEA.3 “We're testing the feasibility of a nanolaser based on GaN nanowires emitting in the ultraviolet,” says researcher Jesús Zúñiga Pérez. Approximately 100 nm across, this laser, integrated on an LOC, could be used to excite organic molecules in a biological sample and analyze the composition of such molecules. But in order to develop these pocket-size labs, researchers need to master fluid dynamics for volumes of less than a nanoliter, and to be able to manipulate biological species right down to the level of a single cell.

Notes :

1. Laboratoire d'analyse et d'architecture des systèmes (CNRS).
2. Institut d'électronique fondamentale (CNRS / Université Paris-XI).
3. Centre de recherche sur l'hétéroépitaxie et ses applications (CNRS).

Contacts :

Anne-Marie Gué,
anne-marie.gue@laas.fr
Jean-Michel Lourtioz,
jean-michel.lourtioz@ief.u-psud.fr
Jesús Zúñiga Pérez,
jesus.zuniga.perez@crhea.cnrs.fr


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