Impedimetric Aptasensors Based on Carbon Nanotubes – Poly(methylene blue) Composite

Abstract

The effect of aptamer structure and immobilization platform on the efficiency of thrombin binding and its detection using electrochemical impedance spectroscopy (EIS) characteristics was investigated with aptasensors based on glassy carbon electrodes covered with multiwalled carbon nanotubes (MWNTs). Aptamers with one or two binding sequences GGTTGGTGTGGTTGG specific for thrombin and poly(dA) and poly(dT) tags able to form dimeric products (aptabodies) were used to establish significance of steric and electrostatic factors in aptasensor performance. We have shown that electropolymerization of methylene blue onto MWNTs significantly improved electrochemical characteristics and sensitivity of thrombin detection against bare MWNTs. Charge transfer resistance and capacitance of the surface layer were measured in the presence of redox probe [Fe(CN) 6 ] 3À/4À . Aptasensors make it possible to detect thrombin in the concentration range 1 nM-1 mM with the limit of detection of 0.7 nM (monitoring resistance changes) and 0.5 nM (capacitance changes), respectively.

Aptasensor for Thrombin Based on Carbon Nanotubes‐Methylene Blue Composites

“…One can see that the MB addition increases the affinity of thrombin binding by one order of magnitude in comparison with parent immobilization techniques. Also, LOD obtained in the presence of adsorbed MB and MWNTs in the surface layer are about three times lower than that of QCM sensor based on electropolymerized MB on bare gold electrode [28]. The effect of MB on analytical performance of MWNTs based EQCM sensor can be related to the electrostatic interactions providing necessary coordination of an aptamer and thrombin at the negatively charged carboxylic terminal groups of MWNTs.…”

“…It has been shown that the sensitivity of detection depends both on the method of immobilization as well as on the method of detection. Most recently we showed high sensitivity of the electrochemical QCM (EQCM) aptasensor based on immobilization of DNA aptamers onto the surface of polymerized MB [28] and on multiwalled carbon nanotubes (MWNTs) formed by electropolymerization of MWNTs with MB at the surface of AT-cut quartz [29]. In this article we compared the sensitivity of the thrombin detection for two receptor systems -the single stranded aptamers and those based on so-called aptabodies.…”

“…The coordination makes MB very sensitive to the changes in the electrostatic interactions followed by aptamers-thrombin interactions. This enhances the sensitivity of amperometric detection of thrombin in comparison with the use of polymeric forms of phenothiazine dyes previously described [28].…”

“…The mechanism proposed assumes the mobility of phenothiazine dye within the surface layer. The electropolymerization of MB on blank GCE makes the appropriate amperometric signal quite stable and insensitive toward thrombin concentration even though the affinity of aptamer-thrombin interaction was found by QCM measurements very high [28].…”

Electrochemical nanomaterial-based nucleic acid aptasensors

“…Moreover, as in the case of metal nanoparticles, CNTs have been used to increase the surface area of working electrodes and to incorporate specific redox probes [98][99][100]. A selective potentiometric sensor using CNTs was developed in the work discussed in Ref.…”