Fabrication of a multi-electrode array DNA sensor form electrochemical genotyping

One of the essential conditions of genotyping is a high precision in detection such as that required in gene diagnosis to detect genetic lesions and mutations. Using a fabricated multi-electrode array (4 by 4) DNA sensor, we were able to distinguish perfectly matched double-stranded DNAs from both single-stranded DNAs and single-base mismatched DNA double strands. Au was used the electrode material, and a photoresist (AZ1512) was used as an insulating layer. 2-mercaptoethanol was used as the self-assembled monolayer for linking the DNA to the Au electrode, and methylene blue (MB) was used as an indicator that could be selectively bound to double-stranded DNA. Using cyclic voltammetry to measure the redox reaction of methylene blue, we observed the reductive peak current of methylene blue when the input voltage of cyclic voltammetry was -260 mV at the working electrode (vs. Ag/AgCl). The measured current of perfectly matched double-stranded DNA was 590 nA at this potential. This value was larger than that of the single-base mismatched DNA double strand (340 nA). Thus, normal double-stranded DNA can be distinguished from a single-base mismatched DNA through an analysis of reductive peak current of methylene blue. This result makes possible a precise electrochemical genotyping using this multi-electrode array DNA sensor which can detect a single-base mismatched DNA double strand in just a few seconds.