Micro- and macro-viscosity relations in high concentration antibody solutions

Area of Science:

• Biophysics
• Protein Formulation
• Analytical Chemistry

Background:

• High concentrations of monoclonal antibodies (mAbs) lead to increased solution viscosity, complicating drug manufacturing and delivery.
• Current viscosity measurements require substantial sample volumes, which are often unavailable during early-stage formulation development.

Purpose of the Study:

• To evaluate fluorescence correlation spectroscopy (FCS) as an ultra-low volume technique for measuring viscosity in concentrated mAb solutions.
• To assess the validity of the Generalized Stokes-Einstein (GSE) relation under molecular crowding conditions.

Main Methods:

• Utilized FCS with fluorescent tracers of varying sizes to measure microviscosities.
• Compared FCS-derived microviscosity measurements with traditional macroviscosity measurements.
• Analyzed the concentration dependence of viscosity using an exponential model and determined the interaction parameter (kD).

Main Results:

• FCS-derived microviscosity measurements correlated with macroviscosity, with similar trends observed across different solvent conditions.
• A link was established between the viscosity concentration dependence parameter (k) and the protein-protein interaction parameter (kD).
• Observed deviations from the GSE relation for similarly sized tracers and crowders, particularly under attractive interaction conditions.

Conclusions:

• FCS is a viable ultra-low volume method for assessing viscosity in concentrated mAb solutions.
• The study provides insights into the relationship between viscosity, molecular crowding, and protein-protein interactions.
• FCS can be applied to screen mAb formulations, aiding in the selection of optimal drug products.