  Here, we report a facile method for electro-addressable functionalization of
a probe comprising of closely spaced three individually addressable carbon
fiber electrodes for detection of nucleic acids. First, a multi electrode array
probe comprising three adjacent carbon fiber electrodes was fabricated through
pulling a three-barrel glass capillary with a single carbon fiber in each
barrel using a micropuller. Second, electropolymerization based doping was used
for electro-addressable functionalization of the multi-electrode array probe.
To demonstrate that the current strategy works, anti-miR-34a was electrografted
on only one of three electrodes by electropolymerization of pyrrole on the
specific electrode. A second electrode was coated only with polypyrrole (PPy)
and the third was left unmodified. Electrochemical impedance spectroscopy (EIS)
was used for analysis and the results clearly showed charge transfer resistance
of the PPy + anti-miR-34a modified electrode increased significantly after
hybridization, while charge transfer resistance of the other two electrodes
remained almost constant. The results demonstrate that the present strategy has
great potential for constructing multiplex nucleic acid micro/nano biosensors
for local and in situ detection of multiple nucleic acid molecules such as
miRNAs at a time.
