Frequency-selective electrokinetic enrichment of biomolecules in physiological media based on electrical double-layer polarization

Abstract

Proteomic biomarkers of interest to the early diagnosis of diseases and infections are present at trace levels versus interfering species. Hence, their selective enrichment is needed within bio-assays for speeding binding kinetics with receptors and for reducing signal interferences. While DC fields can separate biomolecules based on their electrokinetic mobilities, they are unable to selectively enrich biomarkers versus interfering species, which may possess like-charges. We present the utilization of AC electrokinetics to enable frequency-selective enrichment of nanocolloidal biomolecules, based on the characteristic time constant for polarization of their electrical double-layer, since surface conduction in their ion cloud depends on colloidal size, shape and surface charge. In this manner, using DC-offset AC fields, differences in frequency dispersion for negative dielectrophoresis are balanced against electrophoresis in a nanoslit channel to enable the selective enrichment of prostate specific antigen (PSA) versus anti-mouse immunoglobulin antibodies that cause signal interferences to immunoassays. Through coupling enrichment to capture by receptors on graphene-modified surfaces, we demonstrate the elimination of false positives caused by anti-mouse immunoglobulin antibodies to the PSA immunoassay.

On the recent developments of insulator‐based dielectrophoresis: A review

“…Lower frequencies (100–300 kHz) produced pDEP while higher frequencies (1 MHz) produced nDEP . More recent study by these groups reported the use of nanoslit devices for the ultrafast enrichment of biomarkers and label‐free quantification of intracellular mitochondrial modifications . These recent reports further demonstrate the great applicability of iDEP for trapping, enrichment, and manipulating of relevant nanobioparticles of interest.…”

“…Figure D shows nDEP trapping of 200 nm red particles with “low” surface charge, these particles are pushed out of the constriction region by nDEP. Successful trapping of nanoparticles has also been demonstrated in devices with nano‐constrictions, the Swami research group and the Chou research group have worked substantially on this area, some of their findings have been published in collaboration . In 2012 they demonstrated pDEP and nDEP of streptavidin proteins employing a device with nano‐constrictions.…”

Brownian Motion and Large Electric Polarizabilities Facilitate Dielectrophoretic Capture of Sub‐200 nm Gold Nanoparticles in Water

“…In addition to artificial sub‐micron nanoparticles, DEP has recently been applied to smaller biological nano‐objects: proteins, nucleic acids, and extracellular vesicles . In the case of proteins and nucleic acids, the required very high electric field gradients are achieved using sub‐micron and nanometer‐scale electrode gaps, that concentrate the electric field gradients in extremely small volumes.…”

“…[27] DEP is of interest for the development of lab-on-chip analysis methods, [28] and has been used to concentrate plasmonic particles for various modes of Raman spectroscopy. [27,29] In addition to artificial sub-micron nanoparticles, DEP has recently been applied to smaller biological nano-objects: proteins, [30][31][32][33][34] nucleic acids, [35,36] and extracellular vesicles. [37,38] In the case of proteins and nucleic acids, the required very high electric field gradients are achieved using sub-micron and nanometer-scale electrode gaps, that concentrate the electric field gradients in extremely small volumes.…”

Designing Diagnostic and Prognostic Platforms for Analysis and Probing Disease Emergence

“…With nDEP enrichment inside the nanoslit device, no significant difference is observed between the immunoassay with just 50 pg/mL PSA versus that with an additional level (210 4 -fold higher levels) of interfering antimouse IgG antibodies. The kinetic plot in Figure 11b shows that steady-state signals can be reached within 2 minutes of binding under nDEP enrichment of PSA, whereas in the absence of nDEP enrichment the signal does not reach a steady-state level, presumably due to anti-mouse IgG induced non-specific binding that causes false positives [68].…”