The detection of DNA is currently an area of tremendous interest in genetics, clinics, pathology, criminology, pharmacogenetics, food safety, and many other fields. Most NVP-ADW742 ADW742 of DNA biosensors  onto the electrode surface labeled with an electrochemical indicator to recognize its complementary target sequence. CNTs are promising materials for the development of electrochemical DNA hybridization biosensors. The unique properties of CNTs can be united with the specific molecular recognition features of DNA by coupling SWNTs to peptide nucleic acid and hybridizing these macromolecular wires with complementary DNA. Both covalent and non covalent linkage of DNA with CNTs have been reported where the former provide the best stability, accessibility, and selectivity during competitive hybridization.
Figure 4 shows an overview of the covalent attachment process. By this attachment, it was found that DNA molecules BSI-201 are accessible to hybridization and strongly favor hybridization with molecules having complementary sequences compared with noncomplementary sequences. The integration of CNTs with other materials has been also used for the immobilization of DNA. Yang et al. described a sensitive DNA hybridization biosensor based on ZrO2 nanoparticles and MWCNTs. The MWCNTs/nano ZrO2/CS modified GCE was fabricated by dispersing ZrO2 nanoparticles and MWCNTs in CS and oligonucleotides were immobilized on a modified GCE. The hybridization reaction on the electrode was monitored by DPV analysis where electroactive daunomycin was used as an indicator.
Jiao and co workers applied the same approach for DNA biosensor using ZnO nanoparticles instead of ZrO2 nanoparticles. Recently, Ma et al. fabricated an electrochemical DNA biosensor based on LBL self assembly of MWCNTs and GNPs via covalent bonding interaction. Doxorubicin was used as an intercalator and the hybridization events were monitored electrochemically by DPV measurement. The biosensor showed an improved sensitivity with an excellent reproducibility due to the high catalytic activities of GNPs and the ability of CNTs to promote electron transfer reactions. A wide linear response range from 0.5 to 0.01 nM with a detection limit of 7.5 pM for target DNA was achieved. Recently, Niu et al.
used manganese complex of rutin as a redox intercalator with carboxylic acid group functionalized MWCNTs and fabricated DNA biosensor for DNA hybridization detection. The modified electrode dramatically increased the amount of DNA attachment and the sensitivity of the complementary ssDNA detection mostly due to the large surface area and good charge transport characteristics of CNTs. Erdem et al. described a new DNA biosensor based on the enhancement of guanine signal at MWCNTs modified pencil graphite electrode using DPV. PGE behaved as a microelectrode array coupled with its higher porosity and showed improved performance compared to GCE. Another new DNA biosensor based on electrochemical impedance was described by Fang,s group. They modified GCE using a composite material of PPy and carboxylic group terminated MWCNTs.