In-depth insight into the methods of plasma protein-drug interaction studies: Comparison of capillary electrophoresis-frontal analysis, isothermal titration calorimetry, circular dichroism and equilibrium dialysis.

Plasma protein-drug binding assays are routinely performed during the early stages of drug discovery and development, which creates demand for an automated high-throughput screening assay to increase laboratory efficiency. A comprehensive comparison of the four methods typically used for determining the binding parameters is presented in this study with respect to the above demand. Capillary electrophoresis-frontal analysis, isothermal titration calorimetry, circular dichroism and equilibrium dialysis were used to study the affinity of human serum albumin for diclofenac and lidocaine. These model drugs were chosen due to their different physico-chemical properties and different binding sites on the albumin molecule, also resulting in different binding strength. The binding parameters estimated under the conditions as similar as possible were comparable among all these approaches as well as to the literature values. Besides this, the comparison of the results and especially other considerations demonstrated the benefits and drawbacks of the selected methods, with capillary electrophoresis-frontal analysis being the best candidate for such studies.