Microcavity-enhanced energy transfer for biodetection

Schematic diagram : The incident blue light excites fluorescent nanocrystals ("quantum dots", QDs) placed under the surface of a polymer sphere a few micrometers in diameter. Their green fluorescence emission is coupled with so-called whispering gallery modes, in which the light circulates and remains trapped under the surface of the microsphere. When red dyes (dyeNP) in solution come and bind near the surface of the microsphere, for example because of the recognition of a specific biomolecule, they can then be excited by this green light, and re-emit in the red.
New challenges related to public health and the advent of personalized medicine require the development of more sensitive, easy-to-use bio-detection methods that can efficiently detect proteins or other biomolecules in a specific way.

Researchers from the Laboratory of Physics and Study of Materials (LPEM, ESPCI/Sorbonne University/CNRS) have highlighted a new phenomenon that could allow sensitive and simple to implement bio-detection. They have loaded micrometric polymer spheres with fluorescent semiconductor nanocrystals emitting in the green. The fluorescence of the nanocrystals then excites so-called whispering gallery modes, in which the light is trapped by total internal reflection inside the microsphere. For certain wavelengths, the light travels around the circumference of the sphere returning to the starting point with the same phase, forming a resonant cavity in which the light can travel from tens of thousands up to millions of revolutions before escaping. In collaboration with a team of chemists from the Laboratory of Bioimaging and Pathologies (LBP, University of Strasbourg/CNRS), they then placed nanoparticles loaded with red-emitting dyes close to the surface of the microsphere. Thanks to this resonant cavity effect, the green light trapped in the microsphere then excites these red dyes very efficiently, only when they are present in the first few tens of nanometers above the surface. This energy transfer is more efficient and works over a greater distance than the energy transfer phenomena used in different biosensing methods. The two teams are now working to use this phenomenon to develop more sensitive biosensing methods, in which the presence of a target biomolecule would be detected simply by a change in fluorescence color from green to red.

Associated publication :
"Microcavity-Enhanced Fluorescence Energy Transfer from Quantum Dot-Excited Whispering Gallery Modes to Acceptor Dye Nanoparticles"
Jana, Subha ; Xu, Xiang ; Klymchenko, Andrey ; Reisch, Andreas ; Pons, Thomas

Contact chercheur :
Thomas PONS, thomas.pons (arobase) espci.fr

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