Dielectrophoretic (DEP) microarray devices allow important cellular nanoparticulate biomarkers and virus to be rapidly isolated, concentrated and detected directly from clinical and biological samples. A variety of sub-micron nanoparticulate entities including cell free circulating (cfc) DNA, mitochondria and virus can be isolated into DEP high-field areas on microelectrodes, while blood cells and other micron-size entities become isolated into DEP low-field areas between the microelectrodes. The nanoparticulate entities are held in the DEP high-field areas while cells are washed away along with proteins and other small molecules which are not affected by the DEP electric fields. DEP carried out on 20 µL of whole blood obtained from Chronic Lymphocytic Leukemia (CLL) patients showed a considerable amount of SYBR Green stained DNA fluorescent material concentrated in the DEP high-field regions. Whole blood obtained from healthy individuals showed little or no fluorescent DNA materials in the DEP high-field regions. Fluorescent T7 bacteriophage virus could be isolated directly from blood samples, and fluorescently stained mitochondria could be isolated from biological buffer samples. Using newer DEP microarray devices, high molecular weight (hmw) DNA could be isolated from serum and detected at levels as low as 8–16 ng/mL.

BACKGROUND Circulating cell-free DNA (ccf-DNA) is becoming an important biomarker for cancer diagnostics and therapy monitoring. The isolation of ccf-DNA from plasma as a “liquid biopsy” may begin to replace more invasive tissue biopsies for the detection and analysis of cancer-related mutations. Conventional methods for the isolation of ccf-DNA from plasma are costly, time-consuming, and complex, preventing the use of ccf-DNA biomarkers for point-of-care diagnostics and limiting other biomedical research applications. METHODS We used an AC electrokinetic device to rapidly isolate ccf-DNA from 25 μL unprocessed blood. ccf-DNA from 15 chronic lymphocytic leukemia (CLL) patients and 3 healthy individuals was separated into dielectrophoretic (DEP) high-field regions, after which other blood components were removed by a fluidic wash. Concentrated ccf-DNA was detected by fluorescence and eluted for quantification,PCR,and DNA sequencing. The complete process, blood to PCR, required <10 min. ccf-DNA was amplified by PCR with immunoglobulin heavy chain variable region (IGHV)-specific primers to identify the unique IGHV gene expressed by the leukemic B-cell clone, and then sequenced. RESULTS PCR and DNA sequencing results obtained by DEP from 25 μL CLL blood matched results obtained by use of conventional methods for ccf-DNA isolation from 1 mL plasma and for genomic DNA isolation from CLL patient leukemic B cells isolated from 15–20 mL blood. CONCLUSIONS Rapid isolation of ccf-DNA directly from a drop of blood will advance disease-related biomarker research, accelerate the transition from tissue to liquid biopsies, and enable point-of-care diagnostic systems for patient monitoring.

Common epifluorescent microscopy lacks the sensitivity to detect low levels of analytes directly in clinical samples, such as drug delivery nanoparticles or disease related DNA biomarkers. Advanced systems such as confocal microscopes may improve detection, but several factors limit their applications. This study now demonstrates that combining an epifluorescent microscope with a dielectrophoretic (DEP) microelectrode array device enables the detection of nanoparticles and DNA biomarkers at clinically relevant levels. Using DEP microarray devices, nanoparticles and DNA biomarkers are rapidly isolated and concentrated onto specific microscopic locations where they are easily detected by epifluorescent microscopy. In this study, 40nm nanoparticles were detected down to 2–3 × 103/ul levels and DNA was detected down to the 200 pg/ml level. The synergy of epifluorescent microscopy and DEP microarray devices provides a new paradigm for DNA biomarker diagnostics and the monitoring of drug delivery nanoparticle concentrations. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Recent reports of CF-HMW DNA in a variety of diseases has led to interest in its use as a prognostic biomarker, a diagnostic or screening tool for cancer. Apoptotic DNA (&lt;200bp) is present in the circulation of normal healthy individuals. In cancer, unregulated cell growth leads to uncontrolled cell death, or necrosis, which produces HMW DNA (&gt;500bp) that is then trafficked into circulation. Dielectrophoresis, or DEP (movement of particles in a non-uniform AC electric field), based electrokinetic techniques have been used for protein biomarker screening, cell separation, and DNA manipulation. Using specific DEP frequencies, analytes are moved to known locations (high or low field region) based on their inherent dielectric properties. The process allows specific nano-sized particles to be highly concentrated into high field regions, while micron-size cells are held weakly in low field regions. With fluidic washing, cells can be removed while nano-sized particles are held in high field regions. This method can effectively act as a CF-HMW DNA enrichment process for biological fluids. Unfortunately, DEP does not work well in (high conductance) physiological buffers, requiring significant dilution of the sample and, as a result, the target analyte concentration. Here, we describe a novel AC electrokinetic (ACE) technique using a custom microelectrode array and AC parameters to isolate and analyze CF-HMW DNA from high conductance serum. DNA from normal serum samples and the A549 cell line were isolated using Qiagen kits to determine initial DNA quantities. Normal sera were spiked with A549 cell line DNA at concentrations from 0 to 500 ng/ml and subjected to a 20 minute ACE protocol. DNA isolation was visualized in situ using SYBR Green I fluorescence and then eluted for use in secondary analyses. Results showed minimal fluorescence from samples without spike whereas A549 DNA spiked samples showed concentration-dependent fluorescence on the microelectrodes. After elution, levels of DNA were quantitated using ALU-sequence based qPCR and K-ras mutational status was confirmed by ABI CastPCR. Future experiments will compare CF-HMW DNA levels from normal and cancer patients across a variety of solid tumors. The ACE technique enables rapid isolation and detection of CF-HMW DNA directly from biological fluids without prior sample prep and has broad utility for diagnosis and monitoring of cancer and other diseases in which CF-HMW DNA may be used as a marker. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1704. doi:1538-7445.AM2012-1704