Highly sensitive colorimetric detection of DNA hybridisation with high
spatial resolution
R. Wirtz†*, C. Wälti†, W.A. Germishuizen‡, A.P.J. Middelberg‡, A.G. Davies† and M. Pepper†
University of Cambridge, UK
: Semiconductor Physics Group, Cavendish Laboratory
‡
: Department of Chemical Engineering
†
With the possible use of DNA in molecular electronic applications as either a scaffold for conducting wires
[1] or a conducting wire itself [2], the need to assemble and detect DNA on metal electrodes has emerged.
Whilst the use of fluorescent tags to detect DNA on non-metallic surfaces is widely applied in DNA
microarrays, using the same technique on metallic surfaces proves difficult owing to electronic quenching of
fluorescence by the close proximity of the metal surface [3].
Using a colorimetric detection method, we are able to detect biotinylated oligonucleotides hybridised to
thiolated complementary strands bound to a gold surface. Bulk concentrations down to 10 -9 M of
biotinylated oligonucleotides were detectable. Unlike previous colorimetric detection methods [4,5], our
method has the advantage of providing spatial information of the binding event, which is of higher
resolution than that of an optical microscope. In addition it can also be used on a metal surface, unlike
previous colorimetric detection methods. We are able to detect biotinylated single-stranded DNA from a
solution containing a maximum number of only 7000 molecules on a microarray size spot (approx. 40 µm
diameter, see Figure). This is equivalent to a minimum detectable surface coverage of 7108 molecules per
cm2, assuming that all the 7000 molecules in the solution hybridise to the surface. The real minimum
detectable surface coverage is probably even one or two orders of magnitude lower, making our detection
mechanism much more sensitive than, for example, surface plasmon resonance amplified by gold
nanoparticles.
[1] E. Braun, Y. Eichen, U. Sivan and G. Ben-Yoseph Nature 1998, 391, 775.
[2] Y.A. Berlin, A.L. Burin and M.A. Ratner Supperlattice. Microst. 2000, 28, 241.
[3] D.H. Waldeck, A.P. Alivisatos and C.B. Harris Surf. Sci. 1985, 158, 103.
[4] H. Berney, J. West, E. Haeferle, J. Alderman, W. Lane and J.K. Collins Sensor Actuat. B-Chem. 2000, 68, 100.
[5] I. Alexandre et al. Anal. Biochem. 2001, 295(1), 1.
* Semiconductor Physics Group
Cavendish Laboratory
Madingley Road
Cambridge CB3 0HE
United Kingdom
E-mail: rw236@cam.ac.uk
Phone: +44 (0)1223 762924
Fax: +44 (0)1223 334796