Fast Separation of Charged Molecules by Electrodialysis

Dialysis is one of the most used methods for biomolecule separation based on differences in permeability through membranes. In its simple design, the dialysis membrane works as a physical barrier for molecules larger than the size of the membrane pores. Although simple, the diffusion-driven separation process is slow and requires extended times to complete. However, many of the molecules to be separated are charged; therefore the process may be sped up by adding a supplementary driving force of an electrical nature. Although this principle is utilized for molecular separation based on size and charge, the available instruments require a fixed volume of the sample to be enclosed in a sealed compartment for correct functioning. To avoid sample dilution or poor separation due to insufficient volume, we designed an open dialysis chamber to be used for the separation of molecules by size and charge. The chamber was tested for the separation of dyes from solutions of liposomes, and for buffer exchange. The duration of the dialysis process needed for complete equilibration was less than one hour for all tested samples. In conclusion, electrodialysis may offer a low-cost and fast alternative for separation of ions and charged molecules in small samples.