Comparison of Huggins Coefficients and Osmotic Second Virial Coefficients of Buffered Solutions of Monoclonal Antibodies

Jai A Pathak; Sean Nugent; Michael F. Bender; Christopher J Roberts; Robin J Curtis; Jack F Douglas

doi:10.3390/polym13040601

Comparison of Huggins Coefficients and Osmotic Second Virial Coefficients of Buffered Solutions of Monoclonal Antibodies

Polymers (Basel). 2021 Feb 17;13(4):601. doi: 10.3390/polym13040601.

Authors

Jai A Pathak¹, Sean Nugent¹, Michael F. Bender¹, Christopher J Roberts², Robin J Curtis³, Jack F Douglas⁴

Affiliations

¹ Vaccine Production Program (VPP), Vaccine Research Center (VRC), Formulation and Stabilization Sciences Department, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), 9 W. Watkins Mill Rd., Gaithersburg, MD 20878, USA.
² Colburn Laboratory, Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716, USA.
³ Department of Chemical Engineering and Analytical Science, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
⁴ Materials Science and Engineering Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899, USA.

Abstract

The Huggins coefficient k_H is a well-known metric for quantifying the increase in solution viscosity arising from intermolecular interactions in relatively dilute macromolecular solutions, and there has been much interest in this solution property in connection with developing improved antibody therapeutics. While numerous k_H measurements have been reported for select monoclonal antibodies (mAbs) solutions, there has been limited study of k_H in terms of the fundamental molecular interactions that determine this property. In this paper, we compare measurements of the osmotic second virial coefficient B₂₂, a common metric of intermolecular and interparticle interaction strength, to measurements of k_H for model antibody solutions. This comparison is motivated by the seminal work of Russel for hard sphere particles having a short-range "sticky" interparticle interaction, and we also compare our data with known results for uncharged flexible polymers having variable excluded volume interactions because proteins are polypeptide chains. Our observations indicate that neither the adhesive hard sphere model, a common colloidal model of globular proteins, nor the familiar uncharged flexible polymer model, an excellent model of intrinsically disordered proteins, describes the dependence of k_H of these antibodies on B₂₂. Clearly, an improved understanding of protein and ion solvation by water as well as dipole-dipole and charge-dipole effects is required to understand the significance of k_H from the standpoint of fundamental protein-protein interactions. Despite shortcomings in our theoretical understanding of k_H for antibody solutions, this quantity provides a useful practical measure of the strength of interprotein interactions at elevated protein concentrations that is of direct significance for the development of antibody formulations that minimize the solution viscosity.

Keywords: Huggins coefficient; adhesive hard spheres; flexible polymers; hard spheres; intrinsic viscosity; monoclonal antibody; second virial coefficient; static light scattering; viscosity.