Life Sciences Division

Thanks to the automation and miniaturization of bioactive molecule production, large-scale research on this type of compound has boomed over the past decade. Today, the pharmaceutical industry can run high-throughput screening on 96, 384, or 1536-well microplates to reduce the volume of reagents required for a measurement down to just a few microliters. However, given that thousands of these measurements are performed every day, these volumes are still too large. Each screening run still consumes several liters of solvents, generating a large volume of plastic waste (discarded microplates).

What are the solutions available? For several years now, researchers at the CEA Biochips Laboratory have been investigating a solution using droplets of just a few dozen nanoliters in size as tiny reactants. An automated pipetting system deposits these nanodrops in rows on a microscope slide. It then adds reagents and makes a reaction mixture in each droplet.  These droplets are kept secure by coating each slide in a repeating motif template that creates hydrophilic (water-friendly) zones surrounded by hydrophobic (water-repelling) zones. The result is that once the nanodrops are positioned on the slide, they stay glued to the hydrophilic zones where they can be used in the same way as microplate wells. This makes it possible to place over a thousand droplet-wells on a single slide! Furthermore, the robustness of the glass surface means each slide can be reutilized several times over.

The scientists also demonstrated through this research that it is possible to successively perform combinatorial chemical synthesis** of bioactive molecules and then screen them, all on a single slide. This was achieved by investigating the example of an inhibitor of a hepatitis C virus (HCV)*** enzyme called protease NS3, which forms functional viral proteins and is therefore a strategic pharmacological target.

The science team synthesized the NS3 protease inhibitors inside the nanodrops using a modular chemical assembly approach. This technique works like LegoTM, assembling a whole cell bank of inhibitor molecules inside the nanodrops based on the same pre-synthesized chemical building-blocks. The advantage of this approach is that it enables a vast range of active molecules to be created directly on the slide from just limited number of combinatorial building blocks. In this project, the team used a collection of around 200 chemical blocks to synthesize over 20,000 different compounds. The NS3 protease-inhibiting capacity of these molecules was then tested directly on the original slides. After several screening cycles, the researchers were able to identify a shortlist of promising candidate NS3 inhibitors that could be employed as the starting point for a development drive launched to produce new antiviral agents.