A label-free DNA detection method utilizing capacitive touchscreen

Abstract

A touchscreen is an electronic visual display that can detect the presence and location of a touch within the display area. It is generally used in personal digital assistants (PDAs), satellite navigation devices, and smart phones. There are some kind of touchscreen technology according to methods of sensing touch, which are resistive, infrared, surface acoustic wave (SAW), and capacitive touchscreen. Among them, the capacitive touchscreen has been widely used recently because of increasing smart phone users. Basically, touching the surface of the screen induces capacitance changes of electrodes which can be detected by a capacitive touchscreen. In this study, a novel label-free DNA detection system was developed based on the capacitive property of DNA which could be detected by the capacitive touchscreen. For this purpose, we first fabricated the touchscreen panel by patterning the ITO electrodes on the glass panel, and the ITO electrodes were connected to the capacitive touchscreen controller. On the touchscreen panel, the PDMS chamber was covered and ITO electrodes were chemically modified by 3-aminopropyltrimethoxysilane (APTES). For covalent binding of capture probes after spotting, the electrodes were exposed to UV light for 10 min. The capture probe was specifically designed to be complementary to the target pathogen, Chlamydia trachomatis DNA. The capture probe-modified electrodes were rinsed with water and Tris buffer before target addition. To detect target DNA, we applied DNA samples to the capture probe immobilized ITO electrodes and washed with SSPE buffer after 30 min hybridization. In the case of the target DNA in the samples, the capacitance signal of ITO layer increased. On the other hand, when there is no target DNA in the sample, no capacitance change was recorded. With this system, we have successfully detected target DNA in a label-free manner. This new label-free DNA detection strategy has some advantages owing to properties of touchscree...