DNA electrochemical biosensor of methylene blue as the hybridization indicator

A novel electrochemical DNA biosensor system based on methylene blue (MB) as hybridization indicator for DNA hybridization detection was presented in this paper. 5' end -SH modified DNA (HS-DNA) as nucleotide probes were self-assembled onto the surface of Au electrode. The complementary single stranded DNA (ssDNA) was hybridized with this nucleotide probes to form double-stranded DNA (dsDNA) system in Tris-HCl buffer solution (pH=8.0). Compared with the electrochemical signal of HS-DNA electrode, the electrochemical signal of dsDNA electrode system was decreased after the hybridization program. When the methylene blue, as hybridization indicator, was introduced into this system, the cathodic peak current (ΔIp) of Au electrode with dsDNA was increased significantly after the hybridization program. If the target was a mismatching base-pair DNA sequence, the electrochemical signal of electrode would have no changes almost. This result showed that this DNA biosensor system had an excellent sensitivity with a complete complementary DNA sequence. When the target DNA concentration was 5.0×10 -10 mol/L to 1.8×10-9 mol/L, the cathodic peak current of Au electrode system with the MB as indicator was linearly related, and the detection limit was about 5.0×10-10 mol/L.