Crystallization of proteins is performed to determine their 3D structure which needs to be understood for any effective protein engineering, rational drug design, or controlled drug delivery. Currently, large amounts of precious proteins are required for establishing conditions for crystallization. Therefore there is a compelling need to reduce the amount of protein required for screening.

Digital microfluidics using electrowetting is a powerful fluid manipulation technique used to manipulate nanoliter to microliter-sized discrete droplets. Using software control, droplets can be independently and precisely manipulated to setup multiple reactions on a disposable lab-on-a-chip. We have shown the use of digital microfluidics in clinical, genomic, environmental and other biochemical research applications. In this paper we extend the use of our platform to protein crystallization.

Using inexpensive fabrication processes we have developed an electrowetting lab-on-a-chip to setup 24 distinct protein crystallization conditions. The chip accepts 6 reagents and 4 proteins and sets up 6x4=24 conditions (Figure 1). Using this chip we have demonstrated the setup of 4x24=96 crystallization conditions for a model protein Proteinase K (Figure 2). This chip uses only 15nL per condition. Table 1 below lists 16 of these conditions and compares them with experiments on the plate. There is good agreement between hits on plate and on-chip. We have also demonstrated crystallization of lysozyme (Figure 2), glucose isomerase and xylanase on our platform. The same platform can also be used to setup optimization conditions around a hit from the coarse screen.