3D BROwnian motion Microscopy – 3D BROM

For free nanoobjects in liquid environments, Brownian motion plays a major role, underlying an extremely wide range of biological phenomena, specially in cell biology. Taking advantage of the possibilities of heterodyne numerical holography, the present projects aims at developing optical tools for the accurate characterization and understanding of the Brownian motion of gold nanoparticles, and at creating new stochastic nanoscopy techniques using this random motion to develop novel characterization methods.
The precise characterization of Brownian motion will be achieved using a specially developed numerical holography system taking advantage of the computing power of PC graphic cards to enable the real time reconstruction of digital holograms and the 3D tracking of the position of one or several nanoparticles with a precision of 10x10x150 nm3.
This tool will be applied to the study of Brownian motion in crowded environment which, besides being of theoretical interest in physics, is of major importance in biology. In crowded environments (e.g. cell nuclei), diffusion plays a crucial role for transport-limited processes, when proteins (such as transcription factors) must rapidly find a target (e.g. a short DNA sequence). We will address these problems by estimating the ''Mean First Passage Time'' (MFPT) of gold particles.
In parallel, this holographic tool will be used to develop a novel type of near field microscope using the Brownian gold particles as local scatterers of the optical field, extending concepts validated with fluorescent probes in Stochastic Reconstruction Microscopy (STORM) to metallic particles. The random motion of the particles will allow a complete exploration of the sample and a measurement of its optical near field. Metallic nanoantennas on glass substrates will be fabricated and characterized using digital holography and SNOM, and will serve to characterize and illustrate the possibilities of the new stochastic microscope. Eventually, the rotation frequency of anisotropic nanoparticles (rods) will be available using heterodyne holography, giving access to the temperature and viscosity of their local environment.