Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Lab-on-a-chip News: A self-organizing nanoparticle-based molecular sieve is developed to identify and separate DNAs or cells

22.03.2002


Because living organisms contain millions of different molecules, identifying or separating any single one of these from their natural environment in order to carry out research work or perform diagnoses is quite like looking for a needle in a haystack. A number of molecular separation technologies are of course available, and are used by laboratories on a daily basis, but they are often unwieldy and costly. Scientists the world over are therefore attempting to develop a new generation of analytic devices, known as labs-on-a-chip, where all the technological phases of laboratory work are integrated into speedy automated procedures, in what can be deemed to be a single sample to diagnosis step.



CNRS scientists (1) working at the Institut Curie, together with an ESPCI team, have broken new ground in this field, coming closer to such systems with a technology they have called Ephesia (2) . Combining knowledge and tools developed in physics, chemistry, and biology, they have developed an original approach based on the use of self-organizing nanospheres, which handle the key molecule sorting phase within these chips. This new technology paves the way to a whole field of applications both in genetics and in biochemistry, ranging from the study of molecules to medical diagnostics, in particular in oncology with a view to detecting mutations or micrometastases. These new results are to be published by Science magazine on March 22.

A wide range of labs-on-a-chip using very different concepts and materials are currently being developed the world over. The basic idea which they all share is that the various component phases involved in the analysis of given samples are conducted within microchannels (ranging from one tenth to one hundredth of a millimeter) etched onto a microchip. The samples and the substances used to process them, with a view to extracting specific molecules, are injected into these channels and moved about using micropumps, ultra-small pneumatic systems, and electric fields. The device developed by the Institut Curie team is based on a silicone rubber wafer with a 4 cm diameter, within which fine channels have been moulded. This medium was initially developed by G.M. Whitesides at Harvard University in the United States and is well suited for mass production because of its low cost. One of the major issues in developing a lab-on-a-chip involves building molecule-sorting sieves that will operate within these microchannels. This is the problem to which the Institut Curie and ESPCI teams have provided an original solution, interfacing physics, chemistry, and biology.


Ephesia, a novel molecular sieve

Teams headed by Jean-Louis Viovy at the Institut Curie (joint CNRS/Institut Curie research unit UMR 168 "Physico-chimie Curie") and Jérôme Bibette at the ESPCI (Colloids and Nanostructures Laboratory) decided to use magnetic nanospheres (under one thousandth of a millimeter small) which work as tiny magnets in a water-based suspension. When no magnetic field is applied, the nanoparticles do not have any special orientation, and float about in a liquid medium. They are therefore easy to introduce into a channel, however small. When a magnetic field is applied to this suspension, the particles line up following the field lines, and form rigid columns barring the microchannel with a regular array of obstacles. This new device, a product of magnetic nanoparticle chemistry and the corresponding physics, can therefore effectively and spontaneously self-organize a sieve within the chip, in order to separate biological molecules. The molecules are simply introduced into the device, using a very low voltage electric field, and the ancillary channels etched onto the chip. An electric field is also used to push the molecules through the sieve.

A nanoscopic hurdle race

The hurdle race then begins and as in all races, not all runners will cross the finish line at the same time. As larger molecules are the slowest because of the trouble they have making their way around the hurdles, sorting can be performed according to size. In order to see the molecules, an optical system has been devised which catches them when they cross a light beam barring the channel just after the obstacle array. This original approach has three major advantages as compared to all other technologies traditionally used in laboratories (see "Electrophoresis Technologies"). On the one hand, Ephesia is reversible: as mentioned earlier, the obstacle array spontaneously appears when a magnetic field is applied, but it returns to a liquid suspension immediately upon field switch-off. The sieve can therefore easily and automatically be replaced in between runs, thus avoiding deterioration or contamination. On the other hand, Ephesia is adjustable: sieve size can be adapted to that of the molecules or objects to be separated. Finally, Ephesia is very convenient for implementation on miniature devices as the sieve can be set up remotely and without direct contact, through the application of a magnetic field.

From gene analysis to the detection of micrometastases

Ephesia technology developed by Jean-Louis Viovy?s team is currently relevant to large-size DNAs. Up till now, separating these very large molecules involved using a slow and tedious technology known as pulsed-field electrophoresis (which would take about 24 hours). The new technology is a considerable leap forward, insofar as separation time has been brought down to 20 minutes for DNAs with 10 to 200 kilobase pairs, or kbp.

The team?s goal is now to reach the 500 kpb level as soon as possible, in order to allow for the speedy and convenient analysis of all DNAs contained in gene banks, the contents of which are growing ever faster in the framework of major genomics projects. These large DNAs are inter alia involved in research into the large-scale genomic changes occurring in cancer cells.

Other future application of Ephesia are also being contemplated. Jean-Louis Viovy?s team is thus attempting to graft antibodies onto the nanospheres so that they can lock on to specific cell types. Another very promising project was recently initiated in Jean Paul Thiery?s laboratory at the Institut Curie (UMR 144 CNRS/Institut Curie). It involves using the new technology to identify residual cancer cells known as micrometastases that may survive in some patients following initial treatment, in order to help physicians eliminate such cells before they trigger a possible recurrence of the disease.

Scientists at the Institut Curie are also looking into integrating this new concept into a genuine, entirely automated lab-on-a-chip. They hope to develop small, easy to use, economical and speedy devices for biologists and physicians alike, which will have better analytic and diagnostic capabilities than the most sophisticated laboratory apparatus currently available.

(1) CNRS Department of Physics and Mathematics, and CNRS Department of Chemistry.
(2) After the Temple to Artemis with numerous columns, which was repeatedly destroyed and rebuilt during Antiquity.



Catherine Goupillon | alphagalileo

More articles from Life Sciences:

nachricht What the world's tiniest 'monster truck' reveals
23.08.2017 | American Chemical Society

nachricht Treating arthritis with algae
23.08.2017 | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

What the world's tiniest 'monster truck' reveals

23.08.2017 | Life Sciences

Treating arthritis with algae

23.08.2017 | Life Sciences

Witnessing turbulent motion in the atmosphere of a distant star

23.08.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>