Label-free detection ofDNA using high-κLu2Ti2O7 electrolyte-insulator-semiconductors

Abstract

In this study, we propose a disposable poly-N-isopropylacrylamide (PNIPAAm) as an immobilizing biological material based electrolyte-insulator-semiconductor (EIS) device for DNA detection, prepared from a high-κ Lu₂Ti₂O₇ sensing membrane. X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy were used to investigate the structural and morphological features of these films annealed at various annealing temperatures. The high-κ Lu₂Ti₂O₇ EIS device annealed at 900 °C exhibited a higher sensitivity of 60.04 mV/pH, a smaller hysteresis voltage of 3 mV, and a lower drift rate of 0.623 mV h⁻¹ than those at other annealing temperatures. These results are attributed to the large surface roughness and the small number of crystal defects. In the biosensing experiments, the immobilization of a negatively charged single-stranded DNA probe (ssDNA) on the Lu₂Ti₂O₇ surface caused an increase in the reference voltage value, whereas the hybridization of complementary target DNA (cDNA) decreased the reference voltage value. The Lu₂Ti₂O₇ EIS biosensor using a ssDNA-immobilized PNIPAAm gel was successfully used for the detection of DNA hybridization. The detection limit of complementary DNA was as low as 10 pM, and the output signal of the Lu₂Ti₂O₇ biosensor increased linearly with the logarithm of cDNA concentration in the range of 10⁻¹¹ to 10⁻⁴ M.