Development of a cheap and portable sensing system for electrochemical genotyping

This paper reports a cheap and portable electrochemical sensing system, which is based on AT90S8535 one-chip micro-controller, for electrochemical genotyping using a DNA chip. The proposed electrochemical sensing system consists of a signal input part including 555-timer based circuit, a signal detection part including T-feedback amplifier based circuit, a signal control part including AT90S8535, and an output display part. Au was used as the electrode material, 2-mercaptoethanol was used as the self-assembled monolayer for linking the DNA to the Au electrode, and methylene blue was used as an indicator that can be selectively bound to double stranded DNAs. By this sensing system, the measured reductive peak voltage of double stranded DNAs (148 mV) was larger by approximately 74 mV than that of the single stranded DNAs (74 mV). Through the analysis of these values measured from DNA modified electrodes, it is possible to distinguish double stranded DNAs from single stranded DNAs. Thus, the result of genotyping is able to be displayed onto LCD or to be transmitted to a computer in just several seconds.