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ELECTROCHEMICAL DNA BIOSENORS
SUMMARY
What’s a biosensor?
 Electrochemical DNA Hybridization Sensing Strategies
 Inosine based hybridization detection by using carbon paste electrode (CPE)
 Gold nanoparticles based detection of hybridization by using disposable pencil graphite electrode (PGE)
 Detection of Factor V Leiden Mutation by using CPE and PGE from real PCR samples.
 Carbon Nanotubes
 TiO2 nanoparticles
Introduction
 The detection of specific DNA sequences provides the basis for detecting a wide variety of infectious and inherited diseases.
 Traditional methods for DNA sequencing, based on the coupling of electrophoretic separations and radioisotopic detection, are labor intensive and time consuming, and are thus not well suited for routine and rapid medical analysis, particularly for point-of-care tasks.
 Electrochemical hybridization biosensors (genosensors) for the detection of DNA sequences may greatly reduce the assay time and simplify its protocol. Such fast on-site monitoring schemes are required for quick preventive action and early diagnosis.
 Therefore, genosensors have recently been the subject of extensive research activities.
 DNA biosensor scheme
Basic principle of a glucose biosensor
GOX
b-D-glucose + O2 + H2O Gluconolactone + H2O2
Transducer
Analytical signal
PNA vs. DNA
 Electrochemical DNA Hybridization Sensing Strategies
1.Label based
a) Hybridization indicators
– metal complexes
– organic dye molecules
– anticancer agents etc.
b) Labelled probe
- Metal label (Au or Ag-nanoparticles,)
- oligonucleotide containing -SH, -NH2, groups.
2. Label free
– Electrochemical signals of DNA purine bases
guanine, (Inosine), adenine
DNA-Chip technology
 Oxidation signal of DNA bases
 The Factor V Leiden mutation,
 designated as 1691 G > A or R506Q, is the major heritable risk factor for venous thromboembolism.
 This mutation in the coagulation factor V gene results in the resistance of Factor V to inactivation by activated protein C (APC).
 If the coagulation Factor V cannot be inactivated, blood coagulates in venums.
Sequences
Wild-type (WT) capture probe :
5’ – AAT ACC TIT ATT CCT CIC CTI TC – 3’
Wild-type target :
5’ – GAC AGG CGA GGA ATA CAG GTA TT – 3’
Mutant (MT) capture probe :
5’ – AAT ACC TIT ATT CCT TIC CTI TC – 3’
Mutant target :
5’ – GAC AGG CAA GGA ATA CAG GTA TT – 3’
Part I
 An electrochemical DNA biosensor was described for the detection of Factor V Leiden mutation and the discrimination of mutation type using the oxidation signal of guanine in connection with DPV for the first time.
 There have not yet been any literature reports about the detection of heterozygous or homozygous mutations from PCR amplified amplicons by using the guanine signal without any modifications in the native bases or any external labels.
 In this study,
 Inosine substituted synthetic oligonucleotide capture probes related to the wild – type or mutant type amplicons were used and these probes were hybridized with their complementary DNA sequences (target sequence or PCR amplicons) at carbon paste electrode (CPE).

Hello friend I would like to ask can it be implemented on MEMS as well
MEMS based have u tried that