The stability of biologics can be highly dependent on formulation pH. The pH can be screened by buffer exchanging proteins into a variety of buffer salts and running follow-up analytics to determine stability. Current practices for buffer exchange all have limitations. Dialysis requires a large excess of buffer and time. Centrifugal filters and desalting columns are faster, but require more hands-on time. Additionally, all three methods require dilution or concentration steps to reach target protein concentrations. Automating buffer exchange eliminates these bottlenecks, making it easy to explore a greater experimental space.
Grunt removes the buffer exchange bottleneck (Figure 1) by automating a pressure-based ultrafiltration/ diafiltration (UF/DF) method (Figure 2). Buffer exchange is accomplished by repeating cycles of volume measurement, pressurization with gentle orbital mixing and buffer refilling. Grunt, Lunatic and Uncle used in series allows for automated formulation preparation followed by a quick assessment of protein quality and stability. Lunatic enables concentration, mass recovery and sample quality analysis with only 2 μL of sample in a 16- or 96-well format. Uncle multiplexes stability measurements including Tm, Tagg, sizing and polydispersity for up to 48 samples at the same time with 9 μL of sample. Scientists can efficiently study a wider range of formulation conditions when automated buffer exchange is combined with small-volume analytical measurements.
This application note demonstrates how Grunt, Lunatic and Uncle (Figure 3) can be easily combined to create formulations and assess stability. A pH screen from 4.0 to 8.0 was performed using Grunt for buffer exchange and concentrating of a biologic, followed by a formulation quality and stability assessment using Lunatic and Uncle.