Effect of dextran as a run buffer additive in drug-protein binding studies using capillary electrophoresis frontal analysis.

The study of drug-protein interactions by capillary electrophoresis frontal analysis requires establishment of a sufficient mobility difference between the mobility of the ligand and protein. The potential utility of dextran as a run buffer additive to manipulate the electrophoretic mobilities of low molecular weight ligands and protein in capillary electrophoresis frontal analysis binding studies was assessed. It was demonstrated that dextran was effective in improving the separation between the ligands warfarin and flurbiprofen and human serum albumin. Separation of ligand and protein increased with the concentration of added dextran (0-7.5% (w/w)), while molecular weight of the additive (70,000-2,000,000) only had a minor effect. The effect of dextran addition on viscosity and electrophoretic and electroosmotic mobilites was systematically studied. Optimal frontal analysis settings were a compromise between achieving satisfactory separation and acceptable analysis times without loss of plateau peak conditions. No effect of dextran upon the drug-human serum albumin interactions could be detected for the model ligands. Introduction of dextran into the electrophoresis buffer expands the applicability of capillary electrophoresis frontal analysis in drug research to binding interactions between proteins and low molecular weight ligands possessing similar electrophoretic mobilities.