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Nano-Biological Probes

Biology is another field where nanotechnology has real and exciting applications. Biologists are particularly interested in semiconducting nanocrystals (or “quantum dots”) devised in the past few years by physical chemists, which they would like to use as probes to explore biological processes at the molecular scale.

nano biological probes

© S. Godefroy/CNRS Photothèque

A fluorescence microscope is used to follow the movement of molecules inside cells.



These objects are made up of several tens or hundreds of thousands of atoms arranged in a crystal lattice structure, with an overall size of approximately 2-8 nm. When excited by light—a laser, for example—they become fluorescent.
The trick is to attach the quantum dots to biological molecules such as proteins (enzymes, antibodies) or nucleic acids (DNA, RNA). The light emission wavelength can then be chosen by varying their size (the smaller the nanoparticles, the more the emission is shifted towards blue), which would make it possible to distinguish biological processes from one another. “In fact, the nanoparticles behave like tiny light bulbs that can be tracked for several tens of minutes using a microscope,” explains Maxime Dahan, of the Kastler-Brossel Laboratory (LKB).1 “They tell us in real time about the motion and position of the biological players to which they are attached.” Such imaging techniques at the level of individual nanoparticles, which were only just beginning to emerge five years ago, have since been vastly improved and are finding a greater number of applications.
They let us “see” beyond the cell membrane what occurs inside the cell, a region which until now was extremely hard to access. Eventually, by attaching probes of different colors to different proteins, it will be possible to record the motion of all these players simultaneously and study their interactions in vivo. This will improve our understanding of the complexity of the innermost mechanisms of living organisms.
So far, this technology has only been applied to cultured cells, but researchers hope to eventually use it in vivo, which should lead to major improvements in medicine. In particular, by making biological imaging ultrasensitive, it should help both physicians and surgeons identify the smallest tumors and metastasis, on the scale of a hundred thousand rather than a billion cells.

Notes :

1. Laboratoire Kastler Brossel (CNRS / École normale supérieure / Université Pierre-et-Marie-Curie).

Contacts :

Maxime Dahan,
maxime.dahan@lkb.ens.fr


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