(394n) Frequency Dependence of Protein Dielectrophoresis Probed with Insulator Based Devices

Dielectrophoresis (DEP) occurs when polarized particles in a non-uniform electric field move towards (positive DEP) or away (negative DEP) from high electric field gradients. When applied to biomolecules, DEP has great potential as a bioanalytical tool for pre-concentration, fractionation, and separation. However, in contrast to well-characterized biological cells, the mechanism of protein DEP is not well understood limiting its potential for bioanalytical applications. The use of insulator posts (i-DEP) is a novel method that generates inhomogenous electric field gradients within a microchannel. In order to enhance the DEP force on proteins, we combine optical lithography with focused ion beam milling (FIBM) to build an array of nanostructured insulator posts in a microfluidic channel and study the DEP behavior of immunoglobulin G (IgG) molecules under DC and AC conditions. Under DC conditions, IgG molecules move according to positive DEP as reported previously [1]; however, utilizing AC, we observed a change from positive to negative DEP. Our preliminary results show that at 1Hz, IgG molecules concentrate in regions of high electric field gradients indicating positive DEP, however above 5Hz, the particles move away of these regions showing negative DEP behavior. This study indicates that such a novel fabrication process has the potential to improve applications for dielectrophoric separation, concentration, and fractionation of biomolecules.

[1] Nakano A.; Chao T.-C.; Camacho-Alanis F., Ros A. Immunoglobulin G and bovine serum albumin streaming dielectrophoresis in a microfluidic device. Electrophoresis 2011, 32, 2314-2322.