Investigation on Liquid-Liquid Phase Separation in Immunoglobulin G Solutions

Abstract: Liquid-liquid phase separation (LLPS) is an important phenomenon in soft condensed matter that explains many properties of membraneless organelles in living cells. The research on this topic is, therefore, a field with a wide range of applications such as biopharmacy and biomaterials. In this project, we investigate the LLPS of the antibody protein Immunoglobulin G (IgG) by analyzing the liquid dynamics of IgG solutions at a wide range of temperatures with dynamic light scattering (DLS). It was found that the slow component of the autocorrelation function increases with decreasing temperature below 0 °C. This can be attributed to either the number of protein clusters increasing as the sample approaches phase separation or LLPS droplets forming in the solution. LLPS was detected through optical microscopy, visualising the droplet formation in the IgG solution. This work confirms that LLPS can be detected for bovine IgG solutions without the presence of cosolvents and without water freezing in the sample.