Nanofils de silicium pour analyse sensible de biomolécules par spectrométrie de masse et pour l'adressage fluidique de cellules en vue des applications laboratoires sur puce et biopuces.

This work deals with the fabrication of an inorganic silicon nanowires substrate dedicated to the sensitive detection of biomolecules by laser desorption/ionisation mass spectrometry (LDI-MS). This technique, in contrast to the matrix-assisted LDI mass spectrometry (MALDI), allows low mass molecules' (<700Da) analysis without parasitic peaks from the organic matrix. The literature reports the difficulty to determine the parameters linked to the technique's performance. We varied the morphology, composition and surface chemistry of silicon nanowires, and discussed the importance of optical and thermal properties, wetting properties and accessibility of analytes to the laser beam on the silicon nanowires performance. The optimized nanowire's substrate shows a high sensitivity for the detection of low mass molecules (50 times higher than classical MALDI). Moreover, the silicon nanowires substrate was successfully used to follow the course of the methylation reaction of peptides in a biochip format. Furthermore, the substrate integration in a lab on chip was investigated. A 1 µL droplet of a peptide mixture (50.10-15M) was displaced by digital microfluidics (electrowetting on dielectric) and successfully analyzed by LDI-MS. Finally, we developed an original method combining the chemistry and topography of silicon nanowires surface using optical lithography technique: areas with different liquid/solid surface tensions are created this way, enabling localized adhesion of proteins, cells and bacteria.