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Two-Photon Excitation in Life Sciences: From Observation to Action
Frédéric Bolze, Annette Niehl, Manfred Heinlein, Nuria Mjdasiri, Jean-Luc Rehspringer, Nicolas Schaeffer, Pascal Didier,Youri Arntz, Yves Mély, Sylvestre Gug, Alexandre Specht, Maurice Goeldner and Jean-François Nicoud

Two-photon (TP) excitation of organic chromophores is of great interest for decades, as applications of such phenomena from 3-dimentional (3D) microfabrication to optical limiting and optical data storage, are of increasing importance. More recently, two-photon excitation found important applications in biology, notably in two-photon excited microscopy (TPEM) or two-photon photodynamic therapy (2P-PDT). Nevertheless, these techniques were using dyes or sensitizers designed for one-photon processes with low two-photon response. The lack of efficient molecules specifically designed for two-photon applications has led us to design new chromophores for biological applications with increased sensitivity to two-photon excitation and specifically added properties useful in biological media, such as water solubility. Here we describe the molecular engineering of such dyes mainly for cell and small animal observation by TPEM and their conjugation to magnetic nanoparticles and bio-nanoparticles such as viruses.We will then focus on the possibility to use photochemical reaction for cell triggering by two-photon photorelease of biologically active substances the so-called two-photon uncaging.

Keywords: Two-photon absorption, bio-imaging, virus, magnetic nanoparticle, uncaging, neurotransmitters.

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