Nanoparticles with multiple functions for in vivo microscopy.

ELIZABETH A. JARES-ERIJMAN

Los Cocos, Cordoba, Argentina

Conferencia; 9th Latin American Conference on Physical Organic Chemistry (CLAFQO 9), Novena Conferencia Latinoamericana de Fisico-química Orgánica; 2007

Research on luminescent semiconductor nanocrystals (also known as quantum dots) has advanced from electronic materials science to biological applications. In our laboratory, we are interested in devising probes including small molecules and nanoparticles as probes for cellular function. Multiple sites at the surface of the nanoparticles could be exploited to achieve multiple functions. Examples of such functions with special relevance in cellular studies include specific targeting of biomolecules, modulation of the optical properties of the nanoparticles to facilitate tracking, sensing of pH and polarity, and exerting a biological function.We are presently developing several strategies for creating orthogonal methods for specific targeting including ligands and expression probes. In addition, we bind photochromic compounds to the nanoparticle surface to achieve the modulation of the luminescence and color of QDs a method conceived to facilitate the tracking of particles at a selected location in the cell. Finally, we have demonstrated that it is possible to exploit the multiple reactive sites at the surface of the nanoparticle to assemble artificial nucleation centers that exert a biological impact in a cellular event of our interest, namely the aggregation of α-synuclein. α-synuclein is an abundant and natively unfolded pre-synaptic protein (14 kDa) related to the pathogenesis of Parkinson’s disease, where aberrant, amyloid-like deposits of this protein are characteristic. There is growing evidence to the cytotoxicity of α-synuclein oligomerization for motor neurons, and many efforts are devoted to unveil the mechanisms underlying α-synuclein physiological function and pathological self-association. We fused α-synuclein with a 12-aa peptide bearing a tetracysteine tag (CCPGCC) for binding fluorogenic biarsenical compounds (e.g. FlAsH, ReAsH). α-synuclein-conjugated QDs can act as nucleation seeds that induce aggregation of FlAsH-labeled α-synuclein-C4 (α-synuclein-C4-FlAsH). We were able to track simultaneously the fate of both the nucleation seeds and the bulk protein through fluorescence spectroscopy and microscopy in vitro and inside cells and proposed a nucleation-propagation mechanism for α-synuclein fibrillation.