An AC electrokinetic method for enhanced detection of DNA nanoparticles

In biomedical research and diagnostics it is a chatlenge to isolate and detect low levels of nanoparticles and nanoscale biomarkers in blood and other biological samples. While highly sensitive epifluorescent microscope systems are available for ultra low level detection, the isolation of the specific entities from large sample volumes is often the bigger limitation. AC electrokinetic techniques like dielectrophoresis (DEP) offer an attractive mechanism for specifically concentrating nanoparticles into microscopic locations. Unfortunately, DEP requires significant sample dilution thus making the technology unsuitable for biological applications. Using a microelectrode array device, special conditions have been found for the separation of hmw-DNA and nanoparticles under high conductance (ionic strength) conditions. At AC frequencies in the 3000-10000Hz range, 10 mu m microspheres and human T lymphocytes can be isolated into the DEP low field regions, while hmw-DNA and nanoparticles can be concentrated into microscopic high field regions for subsequent detection using an epifluorescent system. Final separation and detection of 150 ng/mL OliGreen fluorescent stained high molecular weight (hmw) DNA in. 1 x TBE buffer (109 mS/m). The DEP field was applied at 10000Hz and 10 volts pk-pk for 5 minutes to group of nine microelectrodes. The green fluorescent image (Ex 505 nm, Ern 520 nm) shows fluorescence from the OliGreen stained hmw DNA concentrated on the 80-micron diameter microelectrodes with the far right column of unactivated microelectrodes showing no concentration of hmw-DNA. (C) 2009 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim