Surface interactions of monoclonal antibodies characterized by quartz crystal microbalance with dissipation: impact of hydrophobicity and protein self-interactions.

Surface adsorption of two monoclonal antibodies (mAb1 and mAb2), with widely different hydrophobicity and self-association behavior in solution, was examined by quartz crystal microbalance with dissipation monitoring to understand how adsorption and protein self-interactions near the surface are impacted by their intrinsic properties. The dependence of mass and viscoelastic properties of the adsorbed protein layer on the type of surface, presence of a surfactant, protein concentration, and pH were examined. Adsorption was significantly reduced in the presence of surfactant for both proteins, but for the more hydrophobic mAb2, residual adsorption remained on polystyrene (PS) and Teflon surfaces. Protein concentration had little impact on the adsorbed protein mass for silicon dioxide surface but had a significant impact for PS and Teflon surfaces. At high protein concentrations, an irreversible layer formed first upon which a reversible layer builds. Reversible adsorption was significantly greater at higher protein concentrations and significantly higher for mAb2, consistent with its higher propensity to reversibly self-associate in solution. The viscoelastic properties suggest that adsorbed protein layer at high protein concentrations is more hydrated. The adsorbed protein layer at lower pH was more hydrated, and possibly more unfolded, consistent with the behavior of the antibody in bulk solution.

Quartz resonator-based approach to ultrasonic rheology of a mixed-phase micellar system.

We report the application of a quartz crystal microbalance with dissipation monitoring (QCM-D) to rheology of mixed-phase micellar systems. This novel application of QCM-D allows for the facile monitoring of complex systems under a variety of conditions. Viscosity measurements were obtained for sodium dodecyl sulfate (SDS) solutions, ranging from 1.0 to 50.0 mg/mL, in the presence and absence of toluene. Toluene was shown to swell SDS micelles as observed through an increase in viscosity, and an inflection point designating the critical micelle concentration (CMC) was clearly visible. Aqueous SDS solutions were also stabilized with sodium chloride (NaCl), up to 1.2 M, and with n-dodecanol in toluene solutions, up to 5.0 vol %. Rodlike micelle formation and swelling with toluene were observed in both cases, supporting previous studies. These studies show that a QCM-D approach to ultrasonic rheology holds potential for the specific study of multiphase systems, non-Newtonian fluids, and low volumes of analyte, aspects highly useful for complex or expensive colloidal dispersions such as micellar or biomolecular solutions.