Nucleic acids circulating in body fluids are drawing great attention due to their potential use for disease diagnostics and
prognostics. Current detection methods have yet to demonstrate the capability to selectively detect the low abundance
nucleic acids. The challenge lies in the separation of circulating DNA from the genomic DNA in normal cells.
Here we present an approach employing a nano-structured tip, which directly concentrates nucleic acids to the tip from a
sample solution. The high aspect ratio tip is able to collect nucleic acid molecules out of a buffer solution by using
dielectrophoretic (DEP) and surface tension force. The DEP force attracts DNA and other biomolecules in the vicinity of
a nanotip from the sample solution. Among the attracted molecules, circulating nucleic acids whose dimensions are
much smaller than the nanotip diameter are selectively captured to the tip while other bioparticles comparable to or
larger than the tip diameter remain in the solution due to surface tension induced force. The concentrated DNA molecules are characterized by SEM, X-ray, and fluorescent microscopy, which demonstrate DNA capturing out of a sample solution having a 1pg/mL DNA concentration. The nanotip-based capturing method will facilitate rapid, but highly sensitive detection of circulating DNA directly from minimally treated- or raw samples.