Entanglement Model of Antibody Viscosity

Abstract

Antibody solutions are typically much more viscous than solutions of globular proteins at equivalent volume fraction. Here we propose that this is due to molecular entanglements that are caused by the elongated shape and intrinsic flexibility of antibody molecules. We present a simple theory in which the antibodies are modeled as linear polymers that can grow via reversible bonds between the antigen binding domains. This mechanism explains the observation that relatively subtle changes to the interparticle interaction can lead to large changes in the viscosity. The theory explains the presence of distinct power law regimes in the concentration dependence of the viscosity as well as the correlation between the viscosity and the charge on the variable domain in our anti-streptavidin IgG 1 model system.

In silico selection of therapeutic antibodies for development: Viscosity, clearance, and chemical stability

“…Recognizing that for mAbs of similar isotype (IgG1 in the present case), the variable domain Fv (and the CDRs within) presumably plays a critical role in defining intermolecular interactions leading to differences in viscosity (8,9), we set out to determine what parameters can be extracted to capture the contributing hydrophobic and electrostatic elements (10,11). It has been postulated recently that such interactions may produce molecular entanglements, leading to increased viscosity (12). We focused on sequence only because this provided the simplest means of data generation and analysis.…”

Protein aggregation and its impact on product quality

“…As such, folded or native dimers and oligomers are not observed until very high concentrations (~ 10 2 mg/mL), or are not observed at all within the range of concentration up the protein solubility limit [14,15]. In some cases, stable dimers and oligomers are a predominant and long-lived species [13].…”

“…In some cases, stable dimers and oligomers are a predominant and long-lived species [13]. In other case they may be small transient clusters [15,16], although there remains debate as to the limitations and interpretation of the available experimental techniques [17–20]. In the opposite extreme, large clusters can be stable and isolated for imaging, providing one can avoid difficulties with metastable or trapped aggregate states [21].…”

“…For case (ii), if the aggregates are compact (e.g., microcrystals or dense amorphous nanoparticles [21]), viscosity is expected to decrease as aggregation occurs, because the proteins have lower net excluded volume. But if one considers aggregates that behave more like extended structures that can entangle with one another, then viscosity is expected to rise as a result of aggregate formation [15,41]. This highlights that the “type” of aggregates that are formed are important for even qualitatively predicting whether aggregation cause positive or negative effects for product quality.…”

Biopharmaceutical Evaluation of Intermolecular Interactions by AUC-SE

“…It should be noted that the effect of aggregates on viscosity requires careful investigation because the shape of aggregates can play an important role on viscosity. Elongated and flexible aggregates have an effect to enhance the viscosity, whereas spherical aggregates reduce the viscosity (Yadav et al 2012;Schmit et al 2014).…”