Thomas Mangeat

High-resolution dose–response screening using droplet-based microfluidics

A critical early step in drug discovery is the screening of a chemical library. Typically, promising compounds are identified in a primary screen and then more fully characterized in a dose–response analysis with 7–10 data points per compound. Here, we describe a robust microfluidic approach that increases the number of data points to approximately 10,000 per compound. The system exploits Taylor–Aris dispersion to create concentration gradients, which are then segmented into picoliter microreactors by droplet-based microfluidics. The large number of data points results in IC50 values that are highly precise (± 2.40% at 95% confidence) and highly reproducible (CV = 2.45%, n = 16). In addition, the high resolution of the data reveals complex dose–response relationships unambiguously. We used this system to screen a chemical library of 704 compounds against protein tyrosine phosphatase 1B, a diabetes, obesity, and cancer target. We identified a number of novel inhibitors, the most potent being sodium cefsulodine, which has an IC50 of 27 ± 0.83 μM.

Gold/Silica biochips: Applications to Surface Plasmon Resonance and fluorescence quenching

We report Gold/Silica biochips for low cost biosensor devices. Firstly, the study of biochemical interactions on silica by means of Surface Plasmon Resonance (SPR) is presented. Secondly, Gold/Silica biochips are employed to reduce the strong quenching that occurs when a fluorophore is close to the gold surface. Furthermore, the control of the Silica-like thickness allows optimizing the distance between the metallic surface and the fluorophore in order to enhance the fluorescent signal. These results represent the first steps towards highly sensitive, specific and low cost biosensors based, for example, on Surface Plasmon Coupled Emission (SPCE) techniques.

Gold/silica thin film for biosensors applications: Metal enhanced fluorescence

The work described here concerns the fabrication of cost-effective biosensors that permit to amplify a fluorescence signal without a complex nano-structuration of the surface. The idea is to put to profit the natural pseudo nano-structuring that is observed when depositing metallic layers by various micro-fabrication techniques. This new architecture consists of a glass substrate. A gold film is deposited on the top of it and a silica layer onto the gold. A dye (Cy5) is then absorbed onto the surface and the fluorescence intensity is measured. This intensity depends on the distance between the dye and the metal. It also depends on the properties of the metallic film. The goal of the work is to determine which gold deposition method leads to the highest fluorescence amplification and which silica thickness is required to achieve this amplification.