Channel height dependent protein nucleation and crystal growth in microfluidic devices

We report on results of a study of protein crystallization in microfluidic devices with different channel heights. Multilayer soft lithography has been used for the fabrication of devices with integrated microvalves and crystallization channels of height in the range from 15 mu m to 180 mu m. To demonstrate the channel height dependent nucleation and crystal growth, a standard batch crystallization solution composed of 60 mg/ml lysozyme, 100 mM acetate buffer pH 4.6 and 1.5 M NaCl was used with minimized sample quantity. Our results show that deep channels favorite the nucleation whereas shallow ones favorite the crystal growth. When the channel height is less than 50 mu m the number of lysozyme crystals is dramatically reduced whereas their mean size is increased. Furthermore, our results also show the feasibility of decoupling nucleation and crystal growth in a stair-like channel which should facilitate the appearance of single crystals suitable for X-ray diffraction. (C) 2009 Elsevier B.V. All rights reserved.