A centrifugal microfluidic device for screening protein crystallization conditions by vapor diffusion

This paper describes a centrifuge-based microfluidic device for performing nanoliter-scale protein crystallization trials by vapor diffusion. By combining the capillary effect and centrifugal force, this device spontaneously and parallelly meters and dispenses protein samples and precipitants into 24 reaction chambers for crystallization screening. Furthermore, the design of two-level capillary stop valves and vapor-diffusion chambers in this device allows vapor transport between the protein droplet and the stored precipitant, perfectly equivalent to that observed in conventional vapor diffusion techniques, which slowly brings the protein droplet into a supersaturation state to nucleate and grow protein crystals. We demonstrate the power of this device by testing it for rapid screening of protein crystallization conditions. Compared with the conventional hanging-drop technique, this device can identify more crystallization conditions and provide a wider range of supersaturation rates, while using two orders of magnitude less protein sample. This centrifuge-based microfluidic device provides a simple and low-cost tool for individual laboratories to rapidly screen initial protein crystallization conditions. (C) 2015 Elsevier B.V. All rights reserved.