Investigation on Adsorption Dynamics of Protein/Tween‐20 Mixture at the Surface of Solution by Surface Pressure Measurement

Armoring the Interface with Surfactants to Prevent the Adsorption of Monoclonal Antibodies

The pharmaceutical industry uses surface-active agents (excipients) in protein drug formulations to prevent the aggregation, denaturation, and unwanted immunological response of therapeutic drugs in solution as well as at the air/water interface. However, the mechanism of adsorption, desorption, and aggregation of proteins at the interface in the presence of excipients remains poorly understood. The objective of this work is to explore the molecular-scale competitive adsorption process between surfactant-based excipients and two monoclonal antibody (mAb) proteins, mAb-1 and mAb-2. We use pendant bubble tensiometry to measure the ensemble average adsorption dynamics of mAbs with and without the excipient. The surface tension measurements allow us to quantify the rate at which the molecules "race" to the interface in single-component and mixed systems. These results define the phase space, where coadsorption of both mAbs and excipients occurs onto the air/water interface. In parallel, we use X-ray reflectivity (XR) measurements to understand the molecular-scale dynamics of competitive adsorption, revealing the surface-adsorbed amounts of the antibody and excipient. XR has revealed that at a sufficiently high surface concentration of the excipient, mAb adsorption to the surface and subsurface domains was inhibited. In addition, despite the fact that both mAbs adsorb via a similar mechanistic pathway and with similar dynamics, a key finding is that the competition for the interface directly correlates with the surface activity of the two mAbs, resulting in a fivefold difference in the concentration of the excipient needed to displace the antibody.

Droplet formation in microfluidic T-junction generators operating in the transitional regime. III. Dynamic surfactant effects

This study extends our previous work on droplet generation in microfluidic T-junction generators to include dynamic interfacial tension effects created by the presence of surfactants. In Paper I [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016322 (2012)], we presented experimental findings regarding the formation process in the squeezing-to-transition regime, and in Paper II [T. Glawdel, C. Elbuken, and C. L. Ren, Phys. Rev. E 85, 016323 (2012)] we developed a theoretical model that describes the performance of T-junction generators without surfactants. Here we study dynamic interfacial tension effects for two surfactants, one with a small molecular weight that adsorbs quickly, and the other with a large molecular weight that adsorbs slowly. Using the force balance developed in Paper II we extract the dynamic interfacial tension from high speed videos obtained during experiments. We then develop a theoretical model to predict the dynamic interfacial tension in microfluidic T-junction generators as a function of the surfactant properties, flow conditions, and generator design. This model is then incorporated into the overall model for generator performance to effectively predict the size of droplets produced when surfactants are present.

Insights into protein-polysorbate interactions analysed by means of isothermal titration and differential scanning calorimetry

Therapeutic proteins formulated as liquid solutions at high protein concentration are very sensitive to chemical and physical degradation. Especially avoiding the formation of protein aggregates is very crucial for product quality. In order to stabilize the colloidal properties of protein therapeutics various excipient are used. Especially the detergents polysorbate 20 and 80 are common. However, the mechanism upon which the detergents protect the protein from aggregation is not really known. The present study investigates the interaction of polysorbate 20 and 80 with different proteins: lysozyme, bovine serum albumin (BSA) and an immunoglobulin. The interaction and binding of the detergents to the proteins is investigated by isothermal titration calorimetry (ITC). From ITC the thermodynamic parameters (DeltaH: change in enthalpy, DeltaS: entropy and DeltaG: free energy) upon binding are derived as well as the binding constant K (a). The thermal stability of the proteins in the presence of the detergent is assessed by differential scanning calorimetry (DSC). The results show that both detergents bind to BSA with K (a) between 8 and 12 x 10(3) M(-1) with DeltaH -50 to -60 kJ/mol (25 degrees C). One to two detergent molecules bind to BSA. The presence of both detergents induces a weak stabilisation of the thermal denaturation properties of BSA. However, the interaction of polysorbate 20 and 80 with lysozyme and the immunoglobulin is quite negligible. The presence of the detergents up to a concentration of 2 mM has no impact on the heat capacity curve neither a destabilisation nor a stabilisation of the native conformation is observed.