Sequence-Specific Electrical Purification of Nucleic Acids with Nanoporous Gold Electrodes.

Nucleic-acid-based biosensors have enabled rapid and sensitive detection of pathogenic targets; however, these devices often require purified nucleic acids for analysis since the constituents of complex biological fluids adversely affect sensor performance. This purification step is typically performed outside the device, thereby increasing sample-to-answer time and introducing contaminants. We report a novel approach using a multifunctional matrix, nanoporous gold (np-Au), which enables both detection of specific target sequences in a complex biological sample and their subsequent purification. The np-Au electrodes modified with 26-mer DNA probes (via thiol-gold chemistry) enabled sensitive detection and capture of complementary DNA targets in the presence of complex media (fetal bovine serum) and other interfering DNA fragments in the range of 50-1500 base pairs. Upon capture, the noncomplementary DNA fragments and serum constituents of varying sizes were washed away. Finally, the surface-bound DNA-DNA hybrids were released by electrochemically cleaving the thiol-gold linkage, and the hybrids were iontophoretically eluted from the nanoporous matrix. The optical and electrophoretic characterization of the analytes before and after the detection-purification process revealed that low target DNA concentrations (80 pg/μL) can be successfully detected in complex biological fluids and subsequently released to yield pure hybrids free of polydisperse digested DNA fragments and serum biomolecules. Taken together, this multifunctional platform is expected to enable seamless integration of detection and purification of nucleic acid biomarkers of pathogens and diseases in miniaturized diagnostic devices.