Weak antibody-cyclodextrin interactions determined by quartz crystal microbalance and dynamic/static light scattering

In a quest to elucidate the mechanism by which hydroxypropyl beta-cyclodextrin (HP beta CD) stabilizes antibodies against shaking stress, two heavily debated hypotheses exist, namely that stabilization is due to HPOCD's surface activity, or due to specific interactions with proteins. In a previous study by Serno et al. (Pharm. Res. 30 (2013) 117), we could refute the first hypothesis by proving that, although HP beta CD is slightly surface active, it does not displace the antibody at the air-water interface, and accordingly, its surface activity is not the underlying stabilizing mechanism. In the present study, we investigated the possibility of interactions between HP beta CD and monoclonal antibodies as the potential stabilization mechanism using quartz crystal microbalance (QCM) and static as well as dynamic light scattering. In the presence of HP beta CD, the adsorption of IgG antibodies in the native state (IgG A) and the unfolded state (IgG A and IgG B) on gold-coated quartz crystals was studied by QCM. Results show that HP beta CD causes a reduction in protein adsorption in both the folded and the unfolded states, probably due to an interaction between the protein and the cyclodextrin, leading to a reduced hydrophobicity of the protein and consequently a lower extent of adsorption. These results were supported by investigation of the interaction between the native protein and HP beta CD using static and dynamic light scattering experiments, which provide the protein-protein interaction parameters, B22 and k0, respectively. Both B22 and ki) showed an increase in magnitude with increasing HP beta CD-concentrations, indicating a rise in net repulsive forces between the protein molecules. This is further evidence for the presence of interactions between HP beta CD and the studied antibodies, since an association of HP beta CD on the protein surface leads to a change in the intermolecular forces between the protein molecules. In conclusion, this study provides evidence that the previously observed stabilizing effect of HP beta CD on IgG antibodies is probably due to direct interactions between the cyclodextrin and the protein. (C) 2013 Elsevier B.V. All rights reserved.