Dielectrophoretic enrichment of low-abundance nanoparticles using a nanotip-concentrator for nanoengineered medicine and biology

Enrichment of low-concentration nanoparticles (NPs) is of great interest in medicine and biology. In particular, the enrichment of biomolecules such as DNA and protein can have broad impacts on disease diagnosis and drug discovery. Currently available methods utilize centrifugation or magnetic field. However, these methods are limited in cumbersome preparation steps and low sensitivity. Electric field-based methods have demonstrated potential for NP enrichment, but conventional planar electrodes trapping NPs are limited in sensitivity and imaging capability. Here, we present a nanotip-concentrator using dielectrophoresis (DEP) for NP enrichment. Unlike conventional planar electrodes, a nanostructured probe-tip can facilitate more sensitive detection of NPs because of high electric field strength. The NP enrichment mechanism is studied through numerical computation, and then validated through experiment using Au NPs. For optimized enrichment of NPs, 8 nm-long oligonucleotides are used to enrich through hybridization reactions, which shows the sensitivity at 10 aM (9 copies in a 1.5 μL sample). The nanotip-concentrator will offer a novel enrichment platform for highly sensitive NP detection and analysis.