Electrostatic gating in carbon nanotube aptasensors

Abstract

Synthetic DNA aptamer receptors could boost the prospects of carbon nanotube (CNT)-based electronic biosensors if signal transduction can be understood and engineered. Here, we report CNT aptasensors for potassium ions that clearly demonstrate aptamer-induced electrostatic gating of electronic conduction. The CNT network devices were fabricated on flexible substrates via a facile solution processing route and non-covalently functionalised with potassium binding aptamers. Monotonic increases in CNT conduction were observed in response to increasing potassium ion concentration, with a level of detection as low as 10 picomolar. The signal was shown to arise from a specific aptamer-target interaction that stabilises a G-quadruplex structure, bringing high negative charge density near the CNT channel. Electrostatic gating is established via the specificity and the sign of the current response, and by observing its suppression when higher ionic strength decreases the Debye length at the CNT-water interface. Sensitivity towards potassium and selectivity against other ions is demonstrated in both resistive mode and real time transistor mode measurements. The effective device architecture presented, along with the identification of clear response signatures, should inform the development of new electronic biosensors using the growing library of aptamer receptors.

Comparison of Duplex and Quadruplex Folding Structure Adenosine Aptamers for Carbon Nanotube Field Effect Transistor Aptasensors

“…The different range of 320 nM to 100 µM for 27-mer adenosine aptamer was chosen as the 27-mer adenosine aptasensor showed no response to adenosine concentrations of 1 nM and the signal became stable at 100 µM. The drain current increased as the adenosine concentration was increased for both aptamer sequences, which is consistent with our previous CNT FET aptasensor and attributed to electrostatic gating [6,15]. The 35-mer aptasensor showed a greater current response compared to the 27-mer aptasensor.…”

“…Carbon nanotube field-effect transistor aptasensors have been demonstrated as an effective semiconducting platform for sensor applications in clinical health diagnostics [ 1 ] for the detection of a variety of targets, including small molecules [ 2 , 3 ], proteins [ 4 , 5 ], and metal ions [ 6 ]. Aptamers have been developed as the primary recognition element in biosensors due to their high specificity and affinity, reproducibility, and small size [ 7 , 8 ].…”

Switchable changes in the conductance of single-walled carbon nanotube networks on exposure to water vapour

“…22,57 An applied potential causes a re-distribution of charges in the solution, imparting a potential on the nanotubes and causing changes in the intensity, position and lineshape of the SWCNT Raman bands. 50 Such changes in the G + and G − bands are observed for the wetted SWCNT networks containing surfactant in the current study (Fig.…”

“…[1][2][3] Individualised, bundled and networks of SWCNTs have been used as an alternative functional material in wide variety of electronic devices including field effect transistors (FETs), [4][5][6][7] transparent conducting films (TCFs), [8][9][10][11][12][13][14] and chemical sensors. [15][16][17][18][19][20][21][22] Networks of SWCNTs (a deposition of nanotubes containing many interconnecting bundles) display the aggregate electrical properties of the constituent SWCNTs, [23][24][25] facilitating the fabrication of devices for such applications in a more scalable and repeatable way. 26,27 Much attention has been focused on advancing methods to sort and process SWCNT samples of at least similar electronic type (i.e.…”

Tuning Electrostatic Gating of Semiconducting Carbon Nanotubes by Controlling Protein Orientation in Biosensing Devices

“…As shown in Figures 4 b and d, the current through these devices decreased stepwise as the concentration of the added TEM‐1 increased, that is, an opposite response if compared to devices functionalized with BLIP2 41AzF . Due to the p‐type nature of our SWCNT‐FETs, the positive charge of the protein complex within the Debye length of the CNTs increases charge carrier repulsion decreasing transconductance [1c, 7b] …”