Dielectrophoresis and shear-enhanced sensitivity and selectivity of DNA hybridization for the rapid discrimination of Candida species

We present a dielectrophoresis (DEP)-based microfluidic chip that is capable of enhancing the sensitivity and selectivity of DNA hybridization using an AC electric field and hydrodynamic shear in a continuous through-flow. Molecular DEP was employed to rapidly trap ssDNA molecules in a flowing solution to a cusp-shaped nanocolloid assembly on a microfluidic chip with a locally amplified AC electric field gradient. The detection time can be accelerated to sub-minute periods, and the sensitivity can reach the pico-molar level due to the AC DEP-enhanced molecule concentration (at an optimal AC frequency of 900 kHz) in a small region (∼100 μm2) instead of the broad area used in a tank reactor (∼106 μm2). Continuous flow in a microchannel provides a constant and high shear rate that can shear off most non-specific target-probe binding to promote the discriminating selectivity. On-chip multi-target discrimination of Candida species can be achieved within a few minutes under optimal conditions.