Voltammetric Application of Polypyrrole-Modified Microelectrode Array for the Characterization of DNA Methylation in Glutathione S-Transferase Pi 1

ABSTRACT

Direct and efficient label-free voltammetric detection of glutathione S-transferase Pi 1 (GSTP1) hypermethylation is reported using a custom-developed 16-channel microelectrode array chip. The microelectrode array chip is used in a dipstick configuration allowing detection of DNA hybridization in a solution volume of only 0.35 mL. Platinum microelectrode disks (n = 16) 30 µm in diameter have been modified with a polypyrrole bilayer before any contact with the oligonucleotides. The attachment of 15-mer Probe DNA to the bilayer is random but controlled by the presence of aliphatic tether groups allowing it to form a bidentate complex with the probe DNA. The voltammetric detection procedure of methylated GSTP1-specific target DNA is combined with bisulfite treatment of target DNA. Changes at the interface of the modified microelectrodes in an array configuration are used to record simultaneously cyclic voltammetry on all of the devices. The detection of hybridization is evaluated statistically by a yes or no event by comparing the changes in recorded cyclic voltammograms before and after exposure to the target DNA. All cyclic voltammograms of the methylated target show a greater percentage change than those with the nonmethylated target exposure and show a greater change in cyclic voltammogram area after methylated target exposure. We observe an average percentage difference of 25.6 ± 4.9% with a variation of 19.1%. These results demonstrate that the fast sensing strategy possesses sensitivity and good specificity. Furthermore, this technology can potentially support rapid, accurate diagnosis and risk assessment of patients with prostate cancer.

KEYWORDS:

• DNA hybridization
• glutathione S-transferase
• label-free biosensor
• prostate cancer
• voltammetric detection

Acknowledgments

We thank Dr Janusz Kowalik for providing the precursors of pTPTC3PO₃H₂. We also thank Dr Hang Chen at the Institute for Electronics and Nanotechnology (IEN) at Georgia Tech for facilitating the fabrication process.

Additional information

Funding

Research reported in this publication was supported by Hampton University’s Minority Men’s Health Initiative (MMHI) through a grant awarded by the National Institute on Minority Health and Health Disparities of the National Institutes of Health under Award Number U54MD00862.