Electrolyte-gated carbon nanotube field-effect transistor-based biosensors: Principles and applications

Abstract

Nowadays, there is a high demand for sensitive and selective real-time analytical methods suitable for a wide range of applications, from personalized telemedicine, drug discovery, food safety, and quality control, to defense, security, as well as environmental monitoring. Biosensors are analytical devices able to detect bio-chemical analytes (e.g., neurotransmitters, cancer biomarkers, bio-molecules, and ions), through the combination of a bio-recognition element and a bio-transduction device. The use of customized bio-recognition elements such as enzymes, antibodies, aptamers, and ion-selective membranes facilitates achieving high selectivity. Among the different bio-transduction devices currently available, electrolyte-gated field-effect transistors, in which the dielectric is represented by an ionic liquid buffer solution containing the targeted analyte, are gaining increasing attention. Indeed, these biotransduction devices are characterized by superior electronic properties and intrinsic signal amplification that allow the detection of a wide rangeofbiomolecules with high sensitivity (down to pM concentration). A promising semiconducting material for bio-transduction devices is represented by carbon nanotubes, due to their unique electrical properties, nanosize, bio-compatibility, and their simple low-cost processability. This work provides acomprehensive and critical review of electrolyte-gated carbon nanotube field-effect transistor-based biosensors. First, an introduction to these bio-sensing devices is given. Next, the device configurations and operating principles are presented, and the most used materials and processes are reviewed with a particular focus on carbon nanotubes as the active material. Subsequently, different functionalization strategies reported in the literature, based on enzymes, antibodies, aptamers, and ion-selective membranes, are analyzed critically. Finally, present issues and challenges faced in the area are investigated,theconclusions are drawn, and a perspective outlook over the field of bio-sensing technologies, in general, is provided.

An Aptasensor Based on a Flexible Screen-Printed Silver Electrode for the Rapid Detection of Chlorpyrifos

“…Afterward, the electrodes were rinsed with DI (deionized) water to remove the excess of 11-MUA and air-dried at room temperature. The -SH group, due to the high affinity to conjugate with noble metals, attaches to the Ag working electrode forming the SAM, while the -COOH group remains free for subsequently amide coupling of the aptamers [ 45 ]. To form a strong amide bond, first, the activation of the -COOH group was performed via EDC/NHS chemistry.…”

“…Therefore, 6 µL of 300 mM of EDC and 35 mM of NHS were dropcasted on top of WE and kept for 1 h as previously employed by Nerantzaki et al [ 46 ]. Afterward, on top of each WE, 6 µL of 1 µM aptamer dispersion (diluted in double-distilled water) was dropcasted and kept at 4 °C for 16 h. The reaction of these chemicals with the -COOH leads to a semi-stable amine-reactive NHS-ester group, which once exposed to the aptamers, reacts with the primary amines (found in aptamers) to form a strong and stable amide bond [ 45 ]. The electrodes were rinsed with DI water to remove the excess aptamers and, finally, incubated with 0.5% of BSA to ensure specific binding.…”

Gas Sensors Based on Single-Wall Carbon Nanotubes

“…In this section, we will focus more on the materials aspect. For details about the design of sensor configurations, please refer to some previous review articles [ 52 , 53 , 54 , 55 ].…”

Nanotube Functionalization: Investigation, Methods and Demonstrated Applications

“…Despite the popularity of research on SWCNT-DNA conjugates, only a small number of works have studied the removal of adsorbed DNA on SWCNTs using biological, physical and chemical treatments [ 103 ]. Numerous biological and pharmacological uses of chitosan, including drug delivery, cancer treatment and biosensors, have been researched [ 146 , 147 , 148 ]. Chitosan could effectively disperse the SWCNTs and provide a suitable biological interface for the immobilization of biomolecules [ 149 ].…”