Monoclonal antibodies (mAb) represent an important class of biologic therapeutics that can treat a variety of diseases including cancer. Despite many advantages, their processing, storage and/or administration remains challenging because of either the high flow environment in processing or presence of hydrophobic interfaces during administration and storage promote mAb aggregation. In this work, we use a combination of dynamic surface tensiometry and a spatially resolved Point RESolved Spectroscopy (PRESS) NMR spectroscopy to investigate the adsorption of a model mAb to the oil-water interface. Experiments were performed on a model mAb that consists of a maltose-based protein with a molecular weight of 155 kDa at different concentrations and temperatures. Dynamic surface tensiometry shows that interfacial tension at the mAb-oil interface decrease over time confirming the adsorption of mAbs to the oil-water interface. Additionally, using localized NMR spectroscopy , the structure of a model mAb was evaluated in the bulk (mAb in sodium phosphate buffer) as well as in incrementally closer voxels (375x1500x1500 mm) that approach a model water-oil interface, as well as voxels at the interface and within the oil. Both short echo time and diffusion-weighted REPRESS acquisitions were acquired from nine adjacent voxel locations in 375-mm steps, with six voxels in the bulk mAb above the interface, one voxel centered at the water-oil interface and two voxels below the interface in the oil. NMR spectroscopy results indicate that REPRESS spectra of mAb approaching the interface differ dramatically from the bulk mAb.
With modification of the PRESS sequence, diffusion- and T2-weighted experiments on the sample at and near the interface were conducted to determine if the changes are a result of aggregation or adsorption to the interface. The apparent diffusion coefficient of the mAb as well as its spin-spin (T2) relaxation were measured. Interestingly, the voxel-selective REPRESS spectra demonstrate conformational changes in the mAb as the hydrophobic interface is approached, but the mAb diffusion coefficient becomes higher at the water-oil boundary, indicating a reduction of the association of potentially aggregated mAb compared to its more entangled bulk counterpart.
With the help Ion Cyclotron Resonance facility at the NHMFL, protein fingerprint of the mAb has been determined and molecular dynamic simulations are being conducted to identify the molecular regions of the mAb that are impacted by adsorption to the interface.
