A novel method to evaluate protein solubility using a high throughput screening approach

Protein solubility is a key parameter affecting the performance of every biotechnological downstream processing operation. Current methods used to determine protein solubility data, however, are often characterized by the need of pure protein crystals and long experimental time frames lying in the range of weeks to months, while other methods often fail to reach the solubility limits due to a too high dilution during the generation of the respective experimental solutions. This article presents an efficient, high throughput compatible method—based on photometric turbidity measurements—which allows a gentle and controlled concentration of the solution while constantly analyzing the solution state. All experimental tools were developed using the robotic liquid handling station Tecan Freedom Evo 200. The ability to combine sample concentration and solution state analysis acts as a basis for the determination of process relevant solubility phase diagrams and analysis of relevant kinetic effects during precipitation. Effects of several buffers on protein solubility and solubility curves of different insulin variants are shown as examples of relevant screening parameters.