Do Carbon Nanotubes contribute to Electrochemical Biosensing?

Abstract

a b s t r a c tCarbon nanotubes have been attracting a lot of interest as electron transfer mediators to enhance electrochemical biosensing. The main reason behind this is usually recognized in terms of augmented electrochemical active surface area. The aim of this paper is to review other phenomena that occur at the electrochemical interface. Three distinct features of these phenomena mainly appear in electrochemical biosensing. We introduce the Cottrell, Randle-Sevčick, and Nernst effects to address these features. By using these features, several electrochemical biosensing systems are investigated. Differences among the proposed systems are presented and analyzed in light of these effects. We finally have demonstrated that carbon nanotubes may induce completely opposite effects when dealing with different biosensing systems. This paper also shows that even seemingly small differences (e.g., changing metabolite as detected by the same enzyme) might result in opposite effects on the same carbon nanotube based sensor. Nevertheless, it is shown that carbon nanotubes, in some cases, confirm their exceptional nature in enhancing the sensor performance by orders of magnitude. The sensitivity increases from 87 ± 62 to 3718 ± 73 nA/M ×cm 2 and detection limit decreases from 7.5 ± 5.3 mM to 84 ± 2 M in case of cyclophosphamide detected by the cytochromes P450 3A4.

Assessments of Surface Coverage after Nanomaterials are Drop Cast onto Electrodes for Electroanalytical Applications

“…It was also proposed that at hin-film diffusion-related effect must be taken into account during the interpretation of the electrochemical signala tt he porous electrode. [16,26,[36][37][38][39][40] However, experiments using coppere lectrodes in this work also indicated that diffusionc an occur all the way to the base electrode surface, especially when relativelyl ow CNT loadings are used, corresponding to 1-5 drops of the coating solution (< 320 mgcm À2 CNTs). Modifying the surfaceb ya dding layers of MWCNTs changes the diffusion regime from ac lassical semiinfinite planar model to ac ombinationo fs emi-infinite diffusion (from the bulk solution to the electrode) and finite thinlayer diffusion (molecules accumulateda nd are trapped in pockets of solution between the porousn anotube layers) models.…”

“…[1,2,17,19,21,22] Controversy regarding their excellent electrochemical properties has been raised in many review papers, [1,[18][19][20][21] and there are severalt heories/models proposed to explain for the potential misinterpretation of electrocatalysis at CNT-modified electrode systems. [16,[23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] As imple alternate explanation for apparent electrocatalysis is often given by the increase in the electrochemically active surfacea rea of the porousw orkinge lectrode from the high-surface-area nanotube film, resulting in larger current values.…”

“…[16,26,[36][37][38][39][40] Surface modification with nanomaterials changes the mass-transport regime to ac ombinationo fs emiinfinite planar diffusion and finite thin-layer diffusion models; failure to consider the latter has led many authors to misinterpret the enhanced electrochemical response for signs of electrocatalysis. Henstridge et al [37] performed digitals imulations to support that ad ecrease in the oxidation potential was solely caused by thin-layer diffusion and there was no change in the electron-transferk inetics.…”

Full Fabrication and Packaging of an Implantable Multi-Panel Device for Monitoring of Metabolites in Small Animals

“…The sensor sensitivity is improved by using nanostructured materials. In our previous works we proved that carbon nanotubes (CNTs) clearly provide great advantages when used in electrochemical biosensing [6], in terms of sensitivity and detection limit. However, since CNTs may be potentially toxic, the biocompatibility of devices incorporating nanomaterials needs to be investigated.…”

E-health: From sensors to systems

“…The current prototype includes: a sensor array, a CMOS mixed-signal chip and a tridimensional integrated coil for receiving inductive power and transmitting data via backscattering. The sensor array is realized with an innovative technology, where Carbon NanoTube (CNT)-nanostructured electrodes enable us to measure metabolites with increased sensitivity and lower detection limits as compared to the state of the art [2]. The integrated electronic and sensor array requires 0.5 mW to operate: the electronic power is harvested by the coil.…”