Dielectrophoretic immobilisation of antibodies on microelectrode arrays

Abstract

A silicon based chip device with a regular array of more than 100,000 cylindrical sub-microelectrodes has been developed for the dielectrophoretic (DEP) manipulation of nanoparticles and molecules in solution. It was fabricated by a standard CMOS (complementary metal oxide semiconductor) compatible process. The distribution of the electrical field gradient was calculated to predict the applicability of the setup. Heating due to field application was determined microscopically using a temperature sensitive fluorescent dye. Depending on voltage and frequency, temperature increase was found to be compatible with protein function. Successful field controlled immobilisation of biomolecules from solution was demonstrated with the autofluorescent protein R-phycoerythrin (RPE) and with fluorescently labelled IgG antibodies. Biological activity after DEP application was proven by immobilisation of an anti-RPE antibody and subsequent binding of RPE. These results demonstrate that the developed chip system allows the directed immobilisation of proteins onto microelectrodes by dielectrophoresis without the need for any chemical modification and that protein function is preserved. Being based on standard lithographical methods, further miniaturisation and on-chip integration of electronics towards a multiparameter single cell analysis system appear near at hand.

Aligned Immobilization of Proteins Using AC Electric Fields

“…The interaction forces responsible for holding the protein molecules at the surface presumably are of hydrophobic nature . The strength of the electric field and field gradient, respectively, close to the electrode surface acting on the protein molecules is so high that the water of the proteins' hydration layer is pushed aside leading to immediate contact between protein and surface.…”

“…So far, however, this phenomenon has not been further investigated with regard to a permanent alignment of proteins. Only recently, we have shown that proteins like antibodies and enzymes can be attracted and permanently immobilized on electrode substrates with AC electric fields while maintaining the proteins' capability to bind antigens or to catalyze enzymatic reactions …”

Functionality of dielectrophoretically immobilized enzyme molecules

“…DEP is a promising method for the immobilization of functional biomolecules without the need to modify either the support or the protein. Only recently has the preservation of protein function of dielectrophoretically immobilized anti‐R‐phycoerythrin antibodies been demonstrated . The purpose of this work is to extend these findings to enzymes, including an investigation of electric parameters and their influence on immobilization and enzyme activity.…”

Protein Dielectrophoresis and The Link to Dielectric Properties

“…[48]. Immobilization of proteins in a microelectrode and nanoelectrode array using DEP have also been reported recently by Hoelzel's group [49,50] and Sanghavi et al . [51] was able to preconcentrate neuropeptides for further electrochemical detection.…”