Gold Nanoparticle-Based Electrochemical DNA Biosensors - Electrochemical DNA Biosensors - page 130

Table 4.5. Label-free electrochemical impedance and conductimetric
genosensors

Modified Electrode Detection

Analyte Substrate Technique Detection Limit Reference

×

10 − 11 M72

DNA PAT transgene GCE EIS 2.4

10 − 12 M

Synthetic DNA strains GCE EIS 73

Synthetic DNA strands SNFETs Conductance 100 fM 71

10 − 14 M

×

Synthetic DNA strands SiO 2 Conductance 5 68

10 − 13 M21

PAT gene sequence GCE EIS 3.1 ×

Thrombin AuE EIS 0.02 nM 70

Synthetic DNA strands Quartzcrystal Conductance 5.0 fmol 74

Synthetic DNA strands Pt Conductance 25 pmol 75

2.3 × 10 − 13 M76 CaMV35S gene fragment CPE EIS

6.7 × 10 − 13 M15

Synthetic DNA strands AuE EIS

5.6 × 10 − 13 PAT gene sequence CPE EIS 69

CaMV35S: 35S promoter from cauliflower mosaic virus; CPE: carbon paste electrode; EIS:
electrochemical impedance spectroscopy; GCE: glassy carbon electrode; PAT: phosphinothricin
acetyltransferase; SNFETs: field-effect transistors based on single-walled carbon nanotube
networks.

between the wanted signal augmentation and the reproducibility of
the assays [27]. Furthermore, strategies involving enlargement of
Au-NPshavebeenemployedaswelltoenhancetheelectroanalytical
signalmonitoringDNA hybridizationevents.
Silver enhancement is based on the reduction of silver ions from
one solution (usually the enhancer) by another (the initiator) in
the presence of Au-NPs [77]. The reduction reaction causes silver
to build up preferentially on the surface of the Au-NPs, giving rise
to a core-shell structure. An illustrative example is the work from
Bonanni et al. [78].Theyusedstreptavidin-coatedAu-NPsandsilver
enhancement kits to amplify the impedimetric signal generated in
a biosensor detecting the DNA hybridization event. The scheme
displaying the sensor preparation procedure is shown in Fig. 4.13.
A good reproducibility was achieved (RSD lower than 8.5%), the
detection limitbeing 11.8 pmol.
The same group discussed recently described impedimetric
detection methods for double-tagged DNA from PCR amplification
of Salmonella spp.[77].Oneofthesemethodsinvolvedamplification
of the impedimetric signal by using a monoclonal IgG1kappa anti-