We have developed the prototype of an integrated apparatus for the rational optimization of crystal growth by mapping and manipulating temperature-precipitant concentration phase diagrams [1]. This so-called crystallization bench comprises a flow cell dialysis set-up to exchange crystallization conditions and control temperature during experiment.
Based on this macro-scale instrument we have focused on a miniaturizing apparatus that allows precise control of the experiment parameters using microfluidics. The first functional microfluidic chips integrating microdialysis with the volume less than 1µL already exist [2]. These microchips have multiple designs in order to perform single or multiple crystallization experiments at the same time. As a proof of principle, the experiments, notably using dyes, have been performed to demonstrate the high resistance of the dialysis membrane, its proper integration in the chip as well as lack of any leakages during the crystallization experiments.
The success of these preliminary studies allows to drive crystallization experiments with model proteins like lysozyme and a plant kinase. The chemical composition in the chip can be systematically exchanged during crystallization experiment using a pressure-driven pump. It enables to investigate a multidimensional phase diagrams.
The materials that compose the chips have been chosen carefully and tested at the ESRF on synchrotron beamline FIP-BM30A in order to limit significant scattering background. These results were compared to traditional crystallization plates used for in-plate crystallization. We demonstrate that these chips are X-ray compatible allowing to collect in-situ diffraction data at room temperature of a large number of protein crystals grown on the chip.