International audienceWe describe a universal, high-throughput droplet-based microfluidic platform for crystallization. It is suitable for a multitude of applications, due to its flexibility, ease of use, compatibility with all solvents and low cost. The platform offers four modular functions: droplet formation, on-line characterization, incubation and observation. We use it to generate droplet arrays with a concentration gradient in continuous long tubing, without using surfactant. We control droplet properties (size, frequency and spacing) in long tubing by using hydrodynamic empirical relations. We measure droplet chemical composition using both an off-line and a real-time on-line method. Applying this platform to a complicated chemical environment, membrane proteins, we successfully handle crystallization, suggesting that the platform is likely to perform well in other circumstances. We validate the platform for fine-gradient screening and optimization of crystallization conditions. Additional on-line detection methods may well be integrated into this platform in the future, for instance, an on-line diffraction technique. We believe this method could find applications in fields such as fluid interaction engineering, live cell study and enzyme kinetics
Here, we describe a plug-and-play microfluidic platform, suitable for protein crystallization. The droplet factory is designed to generate hundreds of droplets as small as a few nanoliters (2 to 10nL) for screening and optimization of crystallization conditions. Commercially-available microfluidic junctions and tubing are combined to create the appropriate geometry. In addition, a "chemical library" is produced in tubing. The microfluidic geometry for a "crystallization agent-based chemical library" is validated by screening crystallization conditions of lysozyme. The microfluidic geometry for a "ligand-based chemical library" is also explored to co-crystallize the protein QR2 with a ligand, for the purposes of structure-based drug design. This platform mixes aqueous phases (containing the protein and the crystallization agent) and organic phases (containing the ligand), during the droplet generation and circulation without using any surfactant. The droplet composition is controlled by the respective flow-rates of the different solutions, and checked by measuring online absorbance. The low volumes involved in the crystallization trials, the speed of execution and the absence of a microfabrication stage make our platform a cheap, easy-to-use and versatile tool for crystallization studies.
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