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.
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