Droplet millifluidic tool for determining phase diagrams of single or mixed proteins

Abstract

The investigation of protein solubility requires high-performance screening tools to map their assembly states depending on physical-chemical conditions. For this purpose, we developed a new simple tool based on tubular droplet millifluidics that allows (i) the generation of a homogeneous mixture of proteins/buffer and/or proteins/biopolymers in a short period of time (~s), (ii) the variation of the composition of the mixtures by adjusting the flow rates, and (iii) the determination of the turbidity of the drop by gray level analysis. The proof of concept of this device, i.e. mixing efficiency, turbidity vs. grey level calibration, was performed using colloidal titanium dioxide (TiO2) dispersions. It was then validated through the establishment of a known phase diagram of biopolymers (ß lactoglobulin / acacia gum). The use of millifluidics reduced the amount of material required by a factor of ten and the experimentation time by a factor of five compared to a conventional tube approach.