Label-Free Flexible DNA Biosensing System Using Low-Temperature Solution-Processed In-Zn-O Thin-Film Transistors
We investigated a novel deoxyribonucleic acid (DNA) sensing system based on low-temperature solution-processed In-Zn-O (IZO) thin-film transistors (TFTs) suggesting an alternative evolutionary line to the traditional DNA biosensors. The IZO TFTs exhibited a favorable microenvironment for adsorbed biomolecule such as DNA to transfer electron, which emerges potential sensing behavior. Superior sensing ability to detect and distinguish 0.45 mu L of 0.1 mu M of target DNA oligomers was secured, and indeed selectivity based on oxidation potentials of each oligomer was achieved. Our IZO TFT had a turn-on voltage (V (ON)) of -1.2 V, on/off ratio of 3.55 x 10(6), and on-current (I (ON)) value of 9.02 mu A in pristine condition. A dry-wet method was applied to immobilize target DNA oligomers on the IZO surface, after which we observed a negative shift of the transfer curve accompanied by a significant increase in the I (ON) and the degradation of the V ON and ON/OFF ratio. Furthermore, the variances in these parameters became increasingly severe following the concentration of target DNA. In addition, the sensing mechanism, oxidation of DNA that had been figured out in our previous research offered selectivity in different types of oligomer based on their capabilities to be oxidized; our biosensors were more sensitive to guanine and cytosine compared with adenine. The biosensor applied on a flexible substrate under the same fabrication conditions obtained exactly analogous sensing behavior. These results suggest a prominent candidate to conventional biosensor area and also its posterior applications by demonstrating remarkable sensitivity, selectivity, and feasibility of flexible device.