Viscosity measurements of antibody solutions by photon correlation spectroscopy: an indirect approach – limitations and applicability for high-concentration liquid protein solutions

Abstract

Photon correlation spectroscopy (PCS) is compared with classic rheological measurements using the cone-and-plate technique for the determination of the viscosity of protein solutions. The potential advantages using PCS are small sample volume and fast determination of zero-shear viscosity. The present study assesses potentials and limitations of the applicability of this method for the determination of viscosity of antibody solutions in protein science development. The principle of the assay is based on the determination of the apparent hydrodynamic radius of commercial available latex beads of known size added to protein solutions. Using the Stokes-Einstein equation, the hydrodynamic radius can be converted to viscosity. Several latex particle sizes and concentrations were evaluated and the assay optimized. The PCS assay for viscosity determination was tested using water/glycerol-mixtures, where the viscosity was measured with rheometer using the cone-and-plate method and also compared with published data. Different protein solutions of bovine serum albumin, lysozyme and monoclonal antibodies were then used and the PCS results were compared with viscosity data obtained by the cone-and-plate method. It could be shown that the PCS assay has limitations for the determination of the viscosity of protein solutions, especially monoclonal antibodies. The main reason is due to protein-latex bead interactions leading to the formation of larger aggregates. The use of surface modification of the latex beads can in principle prevent this interaction.

Impact of aggregate formation on the viscosity of protein solutions

“…29 We proved experimentally that the tracer nanoparticles are stable under the conditions of interest, and that they are not affecting the kinetics of mAb aggregation by successively verifying that: (i) the elevated temperature required to induce mAb aggregation does not destabilize the nanoparticles ( Fig. S4(a), ESI †); (ii) the nanoparticles are stable in the presence of mAb molecules under native conditions ( Fig.…”

Scattering Techniques for the Characterization of Biopharmaceuticals

“…It should be noted that several other critical factors need to be satisfied to successfully conduct these experiments [50,52] that include the following: To do this, one needs to measure the diffusion of a particle of known size, whose scattering significantly overshadows the scattering contributions from the inherent biopharmaceutical that is in solution.…”

A Microliter Capillary Rheometer for Characterization of Protein Solutions

“…It fails whenever a probe particle changes the structure of the fluid to be measured . This failure occurs in highly charged concentrated colloidal solutions, of which protein solutions are a good example . Another failure occurs when the probe particle is small compared with the size of structures in the fluid.…”

“…Another failure occurs when the probe particle is small compared with the size of structures in the fluid. This happens whenever protein solutions form large aggregates and thus become heterogeneous . Guidelines involving a series of double checks to avoid the pitfalls of this method are elaborated by Amin et al…”