Publication
605
Analyst. , 131, 923-929, 2006.
DOI: 10.1039/b609844b
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Subfemtomolar
electrochemical detection of target DNA by catalytic enlargement of the
hybridized gold nanoparticle labels
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Murielle Rochelet-Dequaire, Benoît Limoges and Pierre
Brossier
Contribution from the Laboratoire de Microbiologie Médicale et Moléculaire, Faculté de Médecine et de Pharmacie, 7 Boulevard Jeanne d'Arc, 21000 Dijon, France and the Laboratoire d'Electrochimie Moléculaire, Université de Paris 7-Denis Diderot, 2 place Jussieu,75251 Paris Cedex 05, France ,
After showing the failure of conventional gold-enhancement procedures to amplify
the gold nanoparticle-based electrochemical transduction of DNA hybridization in
polystyrene microwells, a new efficient protocol was developed and evaluated for
the sensitive quantification of a 35 base-pair human cytomegalovirus nucleic
acid target (tDNA). In this assay, the hybridization of the target adsorbed on
the bottom of microwells with an oligonucleotide-modified Au nanoparticle
detection probe (pDNA-Au) was monitored by the anodic stripping detection of the
chemically oxidized gold label at a screen-printed microband electrode (SPMBE).
Thanks to the combination of the sensitive AuIII
determination at a SPMBE with the large amount of
AuIII released from each pDNA-Au, picomolar detection
limits of tDNA can be achieved. Further enhancement of the hybridization signal
based on the autocatalytic reductive deposition of ionic gold
(AuIII) on the surface of the gold nanoparticle labels
anchored on the hybrids was first envisaged by incubating the commonly used
mixture of AuIII and hydroxylamine
(NH2OH). However, due to a considerable nonspecific
current response of poor reproducibility it was not possible to significantly
improve the analytical performances of the method under these conditions.
Complementary transmission electronic microscopy experiments indicated the loss
of most of the grown gold labels during the post-enlargement rinsing step. To
circumvent this drawback, a polymeric solute containing polyethyleneglycol and
sodium chloride was introduced in the growth media to act as an aggregating
agent during the catalytic process and thus retain the enlarged labels on the
bottom of the microwell. This strategy, which led to an efficient increase of
the hybridization response, allowed detection of tDNA concentrations as low as
600 aM (i.e., 104 lower than without
amplification), and thus offers great promise for ultrasensitive detection of
other hybridization events.
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