PNA-microprobe biosensing platform for label-free impedance-based detection of neurodegenerative repeat expansions.

DNA interfaces with 0–3 dimensional materials through physisorption and chemisorption mechanisms acquire unique interfacial character for novel biomedical applications.

We present a PNA-based microprobe sensing platform to detect nucleic acid repeat mutations by electrochemical impedance spectroscopy. The microprobe platform discriminated Huntington’s disease-associated CAG repeats in cell-derived total RNA. This sensitive, label-free, and PCR-free detection strategy has the potential to detect a plethora of length mutation disorders.

We present a PNA-based microprobe sensing platform to detect nucleic acid repeat mutations by electrochemical impedance spectroscopy. The microprobe platform discriminated Huntington's disease-associated CAG repeats in cell-derived total RNA. This sensitive, label-free, and PCR-free detection strategy has the potential to detect a plethora of length mutation disorders.Nucleic acid repeats of various types are responsible for more than 40 genetically transferrable diseases. 1 Their detection has been challenging owing to their length. 2 Current state-of-the-art detection of repeats relies on PCR-based methods and prone to frequent falsepositive and false-negative results. 3 Despite the high sensitivity of the electrochemical techniques, down to attomolar level, 4, 5 there were a few efforts to detect expanded repeats and most of them relied on chemical labelling, detecting short target lengths (maximum 10 repeats), while standing at proof-of-concept level. 6-11 DNA probes were previously proposed for label-free detection of G 4 C 2 repeats in cell-derived RNA by measuring the charge transfer resistance (R ct ) of the interface. 12 Despite the label-free strategy, the sensitivity of the system was lower because difference in the detection signal between abnormal and normal target was only factor of 1.2 and the amount of RNA sample used (1 µg/µL) was relatively high for electrochemical platform. 12 Lower sensitivity of surface-bound probes in electrochemical biosensing may be a challenge due to limited control of probe orientation and density, and low hybridization efficiency on surface. 13,14 Peptide nucleic acid (PNA) probes can mitigate these problems due to the excellent stability and improved hybridization efficiency owing to their electrostatic neutrality and stiff backbone.