Validation of a rapid equilibrium dialysis approach for the measurement of plasma protein binding

Equilibrium dialysis (ED) is one of the most frequently used approaches to investigate drug binding, where the major drawbacks are the time to reach equilibrium (varying between 6 and 24 h), a long assay preparation time and complexity of automation. A rapid equilibrium dialysis (RED) device has recently become commercially available (Pierce Biotechnology, ThermoFisher Scientific, Waltham, MA) offering the potential for reduced preparation and equilibration times. The RED device comprises a Teflon base plate which holds up to 48 disposable dialysis cells. Each dialysis insert is made up of two side-by-side chambers separated by a vertical cylinder of dialysis membrane with a high membrane surface area-to-volume ratio. An independent validation of the RED approach for the measurement of human plasma protein binding (PPB) was carried out as a comparative analysis with standard ED evaluating equilibration time, assay reproducibility and accuracy and ease of use. Using a diverse set of 18 commercially available drugs spanning a range of physicochemical properties we have shown this to be a robust and accurate methodology, with a shorter preparation and dialysis time, capable of being automated as a high-throughput assay for the determination of PPB.