Biology Reference
In-Depth Information
Figure 5.8.
Schematic representation of the immobilization and
hybridization of DNA on the PABSA/TiO
2
nanosheets (adapted from Ref. 41
with permission). See also Color Insert.
event could be monitored through impedance measurements. The
LODobtainedwas1.7pMoftargetprobe(CaMV35Sgenesequence)
with a RSD of 4.91% (for 1.0
μ
M of target DNA) and the biosensor
selectivity was tested with non-complementary and double-base
mismatched sequences. Since this hybridization detection does not
require labeling of the oligonucleotide probe or target prior to the
assay, this procedure results in an advantageous method in terms of
simplicity, non-invasiveness,and low costs.
5.4.2
Electrocatalytic Activity of Osmium Oxide
Nanoparticle Labels
Isoniazid-capped 25 nm osmium oxide nanoparticles (OsO
2
-NPs)
were reported by Gao and Yang [42] as successfully electrocatalytic
tags in a microRNA ultrasensitive detection system, schematized
in Fig. 5.9. The assay employs an ITO electrode with immobilized
capture probes (antisense to microRNAs for testing) and after
hybridization with periodate-treated microRNAs, the OsO
2
-NP tags
are brought to the electrode through a condensation reaction
between isoniazid molecules, grafted onto the nanoparticles and
the 3'-end dialdehydes of the microRNA in a hydrazine PBS buffer.
Thereadoutoxidationpotentialofhydrazinewasdirectlycorrelated
to the concentration of the hybridized microRNA and the assay
