Label-free rapid electrochemical detection of DNA hybridization using ultrasensitive standalone CNT aerogel biosensor.

We report the development of an ultrasensitive label-free DNA biosensor device with fully integrated standalone carbon nanotube (CNT) aerogel electrode. The multi-directional tenuous network of clustered CNT embedding into the CNT aerogel electrode demonstrates linear ohmic and near isotropic electrical properties, thereby providing high sensitivity for nucleic acid detection. Using this device, the target DNA hybridization is detected by a quantifiable change in the electrochemical impedance, with a distinct response to the single-stranded probe alone or double-stranded target-probe complex. The target DNA is specifically detected with limit of detection (LoD) of 1 pM with a turnaround time of less than 20 min, which is unprecedented for a miniaturized CNT aerogel sensor and impedance spectroscopy without an intermediate DNA amplification step. Moreover, this system is able to differentiate between the closely related target sequences by the distinct impedance response rendering it highly specific. To the best of our knowledge, this is the first report showing the use of standalone bare CNT aerogel electrode without any substrate support, coupled with electrochemical impedance spectroscopy, for the detection of DNA hybridization. Altogether, the results show that our system is fast, sensitive and specific for label-free rapid direct DNA detection, promising a novel avenue for bio-sensing.