Label-free detection of DNA using novel organic-based electrolyte-insulator-semiconductor

In this study, we have constructed the first organic field effect sensor based on an electrolyte-insulator-semiconductor structure (OEIS) and applied this novel device to pH and DNA sensing. Variations in the insulator-electrolyte surface potential, which originate from either the change of the ionization states of the insulator surface groups or the binding of charged molecules to the insulator surface, modify the flat band voltage (VFB) of the OEIS sensor. The pH sensing experiments of OEIS sensor showed that the output signal linearly depended on pH solution in the range from pH 2 to pH 12, and an average sensitivity of 44.1 mV/pH was obtained. In the biosensing experiments, the absorption of positively charged poly-l-lysine on the insulator surface resulted in the reduction of the VFB value, whereas the subsequent binding of negatively charged single-stranded DNA probe (ssDNA) via electrostatic interaction increased the VFB value. Furthermore, the ssDNA-immobilized OEIS device was successfully used for the detection of DNA hybridization. The detection limit of complementary DNA was as low as 1 μM, and the output signal of OEIS biosensor linearly increased with the logarithm of complementary DNA concentration in the range from 5 × 10−5 to 10−7 M. The easy and inexpensive fabrication of the OEIS device allows to be served as a potentially disposable and sensitive biosensor.