Dielectrophoretic detection and quantification of hybridized DNA molecules on nano-genetic particles

DNA-DNA hybridization reactions on 100 nm oligonucleotide-functionalized silica nanoparticles are found to sensitively affect the amplitude and direction of the dielectrophoretic mobility of the particles at nanomolar target ssDNA concentrations. Such sensitivity permits visual detection of the hybridization event without fluorescent labeling and confocal microscopy by imaging the cross-over frequency (cof) of the particle suspension on a quadrupole electrode array. Strong correlation with effective particle radius and zeta-potential measurements suggests that the dielectrophoretic cof offers not just sensitive signatures for successful functionalization and hybridization but also those for three distinct DNA surface conformations that appear at different surface densities of hybridized DNA. A properly normalized cof calibration chart allows simplified quantification of the target ssDNA concentrations. These results provide a simple, rapid and portable genetic detection method compatible for use outside the laboratory.