Dielectrophoretic characterization and separation of antibody coated submicrometer latex spheres

The dielectrophoretic behavior of carboxylated 216-nm-diameter latex sphere s has been characterized as a function of both medium conductivity and appl ied field frequency. Dielectrophoretic crossover measurements and analysis were used to characterize the dielectric properties of the particles. The p articles were functionalized with antibodies using 1-ethyl-3-(3-dimethylami nopropyl)carbodiimide (EDAC)-based coupling. Measurements indicated that th e surface conductance of the native particles was 1.2 nS and that this redu ced to a value of 0.7 nS after EDAC treatment and 0.25 nS after antibody co upling. Changes in the dielectrophoretic spectrum of the particles were exp loited to demonstrate the principle of separation of unlabeled and protein- labeled particles. This demonstrates the potential for the development of n ew affinity separation systems based on ac electrokinetic methods.