Dielectrophoretic characterization and separation of antibody-coated submicrometer latex spheres

The dielectrophoretic behavior of carboxylated 216-nm-diameter latex spheres has been characterized as a function of both medium conductivity and applied field frequency. Dielectrophoretic crossover measurements and analysis were used to characterize the dielectric properties of the particles. The particles were functionalized with antibodies using 1-ethyl- 3-(3-dimethylaminopropyl)carbodiimide (EDAC)-based coupling. Measurements indicated that the surface conductance of the native particles was 1.2 nS and that this reduced to a value of 0.7 nS after EDAC treatment and 0.25 nS after antibody coupling. Changes in the dielectrophoretic spectrum of the particles were exploited to demonstrate the principle of separation of unlabeled and protein-labeled particles. This demonstrates the potential for the development of new affinity separation systems based on ac electrokinetic methods.