Sensitivity Control of Label-free DNA Hybridization Detection Based on Poly(thionine)-Modified Glassy Carbon and Gold Electrodes

Abstract

Poly(thionine) (PTH)-modified glassy carbon (PTH-S/GCE and PTH-D/GCE) and gold (PTH-S/Au) electrodes were prepared for the label-free detection of DNA hybridizations and their performances in terms of sensitivity and selectivity were compared. Single-strand probe DNA (pDNA) was immobilized on the PTH films via covalent bonding between the amine (-NH2) group of PTH and the phosphate (PO43-) group at the 5' end of the pDNA. The PTH oxidation current was decreased because of the increase in the stiffness of PTH films. The current was further decreased after the duplex was formed by the hybridization of the target complementary DNA (cDNA). The pDNA/PTH-S/GCE, pDNA/PTH-D/GCE, and pDNA/PTH-S/Au sensors showed excellent sensitivities of ca. 2.1, 55, and 1.9 mu A/cm(2)/nM, respectively, and the detection limits (S/N = 3) were ca. 40.6, 1.5, and 45 pM, respectively, for the hybridization of target cDNA.