Scanning Electrochemical Microscopy Imaging of DNA Arrays for High Throughput Analysis Applications - Applications of Electrochemistry and Nanotechnology in Biology and Medicine - page 132

(A)
(B)
Figure 11. Left: SECM approach curves obtained at a ds-DNA-modified gold sub-
strate in pH 7.2 PBS containing 2 mM K 4 Fe(CN) 6 . The SECM tip was a
25-μm-diameter Pt disk held at a potential of 0.5 V. (A) Unbiased substrate in the
absence of MB (—), substrate biased at -0.4 V in the absence of MB (---), and
substrate biased at -0.4 V in the presence of 2 μM MB (···). (B) Effect of substrate
potential ( E s ) in the presence of 2 μM MB ( E s = -0.1, -0.2, -0.3, and -0.4 V). Cir-
cles show theoretical curves for finite electron-transfer kinetics. Right: (A) SECM
image of a DNA microarray immobilized on a gold disk substrate biased at -0.4V
in pH 7.2 PBS solution containing 2 mM K 4 Fe(CN) 6 and 2 μM MB. Both rows of
spots correspond to (a) ss-DNA, (b) ds-DNA (complementary), (c) ds-DNA (one
base mismatch), (d) ds-DNA (two base mismatches), and (e) ds-DNA (three base
mismatches). The spots are surrounded by 6-mercaptohexanol. The section profile
reveals negative-feedback-mode imaging. (B) SECM image of a DNA microarray
immobilized on a gold disk substrate biased at -0.4 V in pH 7.2 PBS solution con-
taining 2 mM K 4 Fe(CN) 6 and 2 μM MB. Both rows of spots correspond to (a)
ss-DNA, (b) ds-DNA (complementary), (c) ds-DNA (one base mismatch), (d)
ds-DNA (two base mismatches), and (e) ds-DNA (three base mismatches). The
exposed gold surface was blocked with triethylene glycol
mono-11-mercaptoundecyl ether. The section profile describes that the tip current
enhances at the DNA spot showing positive-feedback response. Reprinted with
permission from Ref. 42. Copyright (2008) American Chemical Society.