Label-free DNA detection based on modified conducting polypyrrole films at microelectrodes.
A label-free electrochemical detection method for DNA hybridization based on electrostatic modulation of the ion-exchange kinetics of a polypyrrole film deposited at microelectrodes is reported. Synthetic single-stranded 27-mer oligonucleotides (probe) have been immobilized at 2,5-bis(2-thienyl)-N-(3-phosphorylpropyl)pyrrole film formed by electropolymerization on the previously formed polypyrrole layer. The 27- or 18-mer target oligonucleotides were monitored via the electrochemically driven anion exchange of the inner polypyrrole film. The performance of the miniaturized DNA biosensor system was studied in respect to selectivity, sensitivity, reproducibility, and regeneration of the sensor. Control experiments were performed with a noncomplementary target of 27-mer DNA and 12 base-pair mismatched 18-mer sequences, respectively, and did not show any unspecific binding. Under optimized experimental conditions, the label-free electrochemical biosensor enabled the detection limits of 0.16 and 3.5 fmol for the 18- and 27-mer DNA strand, respectively. Furthermore, we demonstrate reusability of the electrochemical DNA biosensor after successful recovery of up to 100% of the original signal by regenerating the DNA "label-free" electrode with 50 mM HCl at room temperature.
Universidade Estadual Paulista, Instituto de Química de Araraquara, R. Prof. Francisco Degni, s/no C. P.: 355, CEP: 14801-970 Araraquara, SP, Brazil.
Carla dos Santos
Cdos S
Riccardi
Hideko
H
Yamanaka
Mira
M
Josowicz
Janusz
J
Kowalik
Boris
B
Mizaikoff
Christine
C
Kranz
D001483:Base Sequence; D015374:Biosensing Techniques; D004247:DNA / Q000032:analysis*; D015342:DNA Probes; D008839:Microelectrodes; D008904:Miniaturization; D009693:Nucleic Acid Hybridization; D011108:Polymers / Q000737:chemistry*; D011758:Pyrroles / Q000737:chemistry*
D015342:DNA Probes; D011108:Polymers; D011758:Pyrroles; C067635:polypyrrole; D004247:DNA