[Paper Review] Electrochemical Glucose Sensor using Single-Wall Carbon Nanotube Field Effect Transistor

Reetu Raj Pandey, Jie Liang+3 more|ArXiv.org|Jun 8, 2020

Electrochemical sensors and biosensors21 references4 citations

TL;DR

This study presents a highly sensitive, low-cost glucose sensor based on a single-wall carbon nanotube field-effect transistor (SWCNT-FET) functionalized with glucose oxidase (GOx) via 1-pyrenebutanoic acid succinimidyl ester linkers. The sensor detects glucose by transducing analyte-induced electron transfer into a measurable current change in real time, achieving detection at 0.01 mM glucose with enhanced sensitivity due to well-dispersed CNT networks and efficient electron transfer through functionalized CNTs.

ABSTRACT

In this paper, we present a simple yet sensitive method for glucose sensing using carbon nanotube field-effect transistor (CNTFET) based biosensor. The CNTs were well-dispersed to form CNT networks and maintain functional connectivity among CNTs, which increases the electron transfer through the network and thus, the electronic readout. Moreover, glucose oxidase (GOx) molecules are immobilized by CNT functionalization to form effective and sensitive CNT networks as FET channel. The CNTs are functionalized with linkers (1-pyrenebutanoic acid succinimidyl ester) to immobilize GOx on CNTs, where GOx serves as a mediator between CNTs and glucose for electron transfer. The liquid analyte glucose is adsorbed on CNTs via GOx and linkers by releasing additional electrons in the CNTFET channel and thus, increasing the CNTFET readout current. The binding of the target glucose molecules and GOx emulates the gate potential of FET channel and the electronic response of the sensor is recorded in real-time. Moreover, the variations in electronic readout of CNTFET biosensor are observed and is stipulated due to variation in CNT dispersion on each device. Overall, this work presents a simple, fast, sensitive, low-cost, and low concentration (0.01 mM) detection of glucose using CNTFET sensors.

Motivation & Objective

• To develop a simple, fast, and low-cost glucose biosensor for clinical and point-of-care applications.
• To enhance electron transfer and sensor sensitivity by creating well-dispersed, functionally connected single-wall carbon nanotube (SWCNT) networks.
• To immobilize glucose oxidase (GOx) on SWCNTs via specific chemical linkers for effective bioelectrochemical transduction.
• To enable real-time, label-free detection of glucose by monitoring changes in CNTFET current in response to analyte binding.
• To achieve detection at ultra-low glucose concentrations (0.01 mM) using a field-effect transistor architecture.

Proposed method

• Single-wall carbon nanotubes (SWCNTs) were dispersed in solution using surfactants to form percolating networks with high electrical connectivity.
• The SWCNTs were functionalized with 1-pyrenebutanoic acid succinimidyl ester (PBASE) to enable covalent immobilization of glucose oxidase (GOx) molecules.
• GOx was covalently attached to the functionalized CNTs, creating a bioelectrochemical interface where glucose oxidation generates electrons.
• The functionalized CNT network served as the FET channel, with the gate potential modulated by the binding of glucose to GOx, altering the channel conductance.
• Electrochemical response was measured in real time as changes in drain current (Id) under applied gate and drain voltages.
• The sensor response was correlated with glucose concentration to determine sensitivity and limit of detection.

Experimental results

Research questions

• RQ1 Can a SWCNT-FET biosensor achieve sensitive and selective glucose detection at low concentrations using enzyme-functionalized nanotubes?
• RQ2 How does CNT dispersion and network connectivity influence the electronic response and sensitivity of the FET sensor?
• RQ3 To what extent does GOx immobilization via PBASE linkers enhance electron transfer efficiency in the biosensor?
• RQ4 Can the FET response mimic a gate voltage modulation due to glucose binding, enabling real-time electronic transduction?
• RQ5 What is the limit of detection for glucose using this CNTFET-based biosensor platform?

Key findings

• The sensor achieved a detection limit of 0.01 mM glucose, demonstrating high sensitivity at ultra-low concentrations.
• Well-dispersed SWCNT networks significantly enhanced electron transfer and improved sensor response reproducibility.
• Functionalization with PBASE linkers enabled stable and efficient immobilization of glucose oxidase on CNTs, enhancing bioelectrochemical activity.
• The electronic response of the CNTFET increased with glucose concentration, indicating a measurable current change due to analyte-induced electron transfer.
• Real-time monitoring of current changes confirmed dynamic response to glucose addition, validating the sensor's suitability for continuous monitoring.
• Variations in device response were attributed to differences in CNT dispersion across individual devices, highlighting the importance of fabrication control.