By Deyong Zhu, Xiaohu Zhou and Professor Bo Zheng of The Chinese University of Hong Kong, China

This paper reports the design and construction of a plastic-glass hybrid microfluidic platform for performing protein crystallization trials in nanoliter double emulsions. The double emulsion-based protein crystallization trials were implemented with both the vapor-diffusion method and microbatch method by controlling the diffusion of water between the inner and outer phases and by eliminating water evaporation. Double emulsions, whose inner and outer environments can be easily adjusted, can provide ideal conditions to explore protein crystallization with the advantages of a convection-free environment and a homogeneous interface. The property of the water-oil interface was demonstrated to be a critical factor for nucleation, and appropriate surfactants should be chosen to prevent protein adsorption at the interface. The results from the volume effect study showed a trend of fewer crystals and longer incubation time when the protein solution volume became smaller, suggesting that the nucleation in protein crystallization process can be controlled by changing the volume of protein solutions. Finally, sparse matrix screening was achieved using the double emulsion-based microbatch method. The double emulsion-based approach for protein crystallization is a promising tool for enhancing the crystal quality by controlling the nucleation process.

Figure 7. Crystallization results of lysozyme in plugs (a,d), droplets (b,e) and double emulsions (c,f). 

Figure 9. Effects of the protein solution volume in plugs, single droplets and double emulsions on protein crystallization. 

Figure 11. Polarized light photographs showing the screening results for thaumatin under three successful screening conditions.

Zhu, D.; Zhou, X.; Zheng, B. A Double Emulsion-Based, Plastic-Glass Hybrid Microfluidic Platform for Protein Crystallization. Micromachines 2015, 6, 1629-1644; doi:10.3390/mi6111446.

This article belongs to the Special Issue Droplet Microfluidics: Techniques and Technologies. http://www.mdpi.com/2072-666X/6/11/1446