Inclusion of mPRISM potential for polymer‐induced protein interactions enables modeling of second osmotic virial coefficients in aqueous polymer‐salt solutions

Abstract

The downstream processing of therapeutic proteins is a challenging task. Key information needed to estimate applicable workup strategies (e.g. crystallization) are the interactions of the proteins with other components in solution. This information can be deduced from the second osmotic virial coefficient B22 , measurable by static light scattering. Thermodynamic models are very valuable for predicting B22 data for different process conditions and thus decrease the experimental effort. Available B22 models consider aqueous salt solutions but fail for the prediction of B22 if an additional polymer is present in solution. This is due to the fact that depending on the polymer concentration protein-protein interactions are not rectified as assumed within these models. In this work, we developed an extension of the xDLVO model to predict B22 data of proteins in aqueous polymer-salt solutions. To show the broad applicability of the model, lysozyme, γ-globulin and D-xylose ketol isomerase in aqueous salt solution containing polyethylene glycol were considered. For all proteins considered, the modified xDLVO model was able to predict the experimentally observed non-monotonical course in B22 data with high accuracy. When used in an early stage in process development, the model will contribute to an efficient and cost effective downstream processing development.

Non‐monotonic course of protein solubility in aqueous polymer‐salt solutions can be modeled using the sol‐mxDLVO model

“…The solubility model (sol-mxDLVO) is a unique combination of the mxDLVO model, which can predict B 22 data of proteins, developed in a previous work [10] and a solubility equation developed in this work.…”

“…In this work, the potential of the mean force W 22 (r) is calculated using the modified xDLVO (mxDLVO) model developed and described in more detail in our previous work [10,[17][18][19][20][21]. The mxDLVO model describes the potential of the mean force W 22 (r) as the sum of the hardsphere potential W HS (r), the dispersion potential W disp (r), the electrostatic potential W el (r), the osmotic potential W osm (r), and the modified PRISM potential W mPRISM (r), as shown in Eq.…”

“…However, the mxDLVO model was used for the modeling of B 22 data. The parameters of the mxDLVO model are taken from Herhut et al [10] and Marcus [22].…”

“…By using an extension of the xDLVO model (mxDLVO), we recently demonstrated the possibility of calculating B 22 data for lysozyme and D-xylose ketol-isomerase in aqueous polymer-salt solutions as a function of polymer concentration [10]. In the present work, we modify the original B 22 solubility equation to calculate protein solubility in polymer-containing solutions to complete the solubility model.…”

Osmotic Virial Coefficients as Access to the Protein Partitioning in Aqueous Two-Phase Systems

“…It was previously shown by Herhut et al and George and Wilson that the intermolecular interactions between protein molecules in solution, as well as the interactions of protein molecules with other molecules in solution can be used to predict process conditions for protein precipitation/crystallization. Within the work of George and Wilson and Bonneté et al, the second osmotic virial coefficient B 22 is used to characterize the interactions between molecules of one species (e.g., protein–protein).…”