Control of concentration and volume gradients in microfluidic droplet arrays for protein crystallization screening

A novel screening platform for the screening and optimization of protein crystallization is reported. Here we present two key experiments to generate protein crystallization phase diagrams. One is to precisely generate spatial gradient droplet arrays; the other is to trap and identify each droplet in place in order to carry out temporal and spatial analysis. The generated concentration and volume gradient ranges from 0% to 100% and from 155 to 310 pico liters, respectively. Furthermore, the active trapping of a droplet array in a microfluidic chip for hours to days to study the dynamic phase changes in protein crystallization is demonstrated. This microfluidic platform can be used for rapidly generating the solubility diagram for protein in various salt solutions.