Single‐Walled Carbon Nanotubes Modified Gold Electrodes as an Impedimetric DNA Sensor

Abstract

A gold surface modified with a self-assembled monolayer of 11-amino-1-undecanethiol (AUT) was used for the covalent immobilization of oxidized single-walled carbon nanotubes (SWNTs). The as-described SWNTs-modified substrate was subsequently used to attach single-stranded deoxyribonucleic acid (ssDNA) used as a substrate for DNA hybridization. Electrochemical impedance spectroscopy measurements were performed to follow the DNA hybridization process by using the redox couple [Fe(CN) 6 ] 3À/4À as a marker ion. Specifically, changes in charge transfer resistance obtained from the Nyquist plots were used as the sensing parameter of DNA hybridization. The substrate sensitivity towards changes in target DNA concentration, its selectivity toward different DNA sequences and its reusability are successfully demonstrated in this report.

Electrochemical DNA Hybridization Sensors Based on Conducting Polymers

“…The distinctive electrical, thermal, chemical, mechanical, and 3-D spatial characteristics of CNTs suggest that it is possible to construct DNA biosensors with high sensitivity, selectivity, and multiplexing by exploiting Watson–Crick base-pairing [ 93 ]. Rodriguez et al covalently attached single-walled CNTs (SWNTs) to a gold surface modified with 11-amino-1-undecanethiol (AUT) and subsequently immobilized a DNA probe on the Au/AUT/SWNTs through covalent linkage [ 94 ]. The interaction and covalent immobilization of DNA probes on functionalized CNTs and CNT/CP-composite-modified electrodes have been widely studied [ 95 , 96 ].…”

Label‐free indicator‐free nucleic acid biosensors using carbon nanotubes

“…In all the above cases, the nanotubes form the active component of the biosensing electrode. However, they can also be used as additives to improve the electrical and electrochemical characteristics of other standard bulk electrodes such as glassy carbon electrode (GCE) , carbon paste electrode , graphite electrode , or gold electrode. For example, CNTs can be incorporated into a polymer matrix on the surface of such bulk electrodes (see Fig.…”

“…A). In many cases, the CNT surface contains carboxyl groups, and probe DNA with a terminal amino group is used for the functionalization . The most common linking strategy involves the use of EDC/NHS (1‐ethyl‐3‐(3‐dimethylaminopropyl)carbodiimide hydrochloride/ N ‐hydroxysuccinimide), which activates the carboxyl groups on the nanotube surface, allowing for the coupling to the amino group of the DNA resulting in an amide bond.…”

“…This increases the “charge transfer resistance,” which serves as a sensor signal for the amount of target analyte bound to the probe . The detection here is mainly performed using impedimetric techniques in order to obtain a good signal‐to‐noise ratio . The sensitivity and the detection limit are usually improved when using indicators.…”

Quantum dot-based microfluidic biosensor for cancer detection

“…This may further be correlated with the probe DNA hybridization with the complementary DNA strands, resulting in the doublestranded DNA helix formation that increases the negative charge of the electrode surface and consequently the R ct . 9,11,22 On incubation with the non-complementary DNA, negligible change in the R ct value is observed (7.2 kX; curve ii) suggesting that there is no double-stranded DNA formation occurring at the biochip surface. Since, the noncomplementary DNA bases do not match the probe DNA bases, it is expected that hybridization event should not take place.…”