The aging of our society leads to a development of neurodegenerative disease like Alzheimer's disease. Patients require an important caring by their family and specialized organisms. Moreover, the mechanisms which lead to the disease are not very well known yet, and progresses in the understanding of these should help to find new treatment. Memory and compartmental troubles associated to Alzheimer's disease come from neuronal and synaptic losses. A scenario proposed to explain those losses is the aggregation of a small protein, β-amyloid, in neuronal area. It leads to the formation of senile sheets at neuron surface which is characteristic of Alzheimer's disease. The reaction is multifactor: it is influenced by β-amyloid concentration, metallic ions, temperature, surface's property. Furthermore, the classical tools of biochemistry can hardly assess the first kinetic steps of aggregation. In this context, this thesis describes original microfluidic tools to study β-amyloid aggregation, according to two approaches. In the first one, concentration gradients combined to on-chip triggering of the aggregation enable screening reaction's conditions. We have essentially tested the impact of β-amyloid concentration and we show a concentration threshold. The second design is devoted to studying the reaction kinetics. We used reaction-diffusion chip to measure the diffusion coefficient with and without aggregation. It should enable measuring the evolution of the size of aggregates. We have successfully determined the diffusion coefficient for some model β-amyloid peptides. However, in aggregating conditions, adsorption of the peptide on the wall still prevents quantitative interpretation of our experiments. With this thesis, we have developed microfluidics tools to study β-amyloid aggregation. In the first part we develop a chip able to screen many reaction conditions. In the second part, we make reaction-diffusion chip to have information about aggregation's kinetics. The main limitation of this chip is the control of peptide interaction with surfaces.
Outils microfluidiques pour la maladie d'Alzheimer: Etude de l'agrégation de l'amyloïde-B