Electrical conductance change of graphene-based devices upon surface modification for detecting botulinum neurotoxin

Abstract

We report an electric conductance change in a graphene-based device upon molecular adsorption for detecting botulinum neurotoxin (BoNT) using the antibody–antigen binding strategy. This device consists of a 400-µm-wide monolayer of graphene between the source and drain electrodes. As-fabricated devices exhibit p-type behaviors. After modifying graphene with linkers and antibodies, BoNT detection was performed by dropping a target solution and measuring the conductance change of the devices. The immobilization of linkers on graphene decreases the electrical conductance as a result of electron transfer from linkers to graphene. However, the conductance change caused by the adsorption of antibodies or BoNTs is ascribed to the top-gating effects of the molecules adsorbed on graphene. The normalized conductance change of the graphene-based device upon antibody–BoNT binding was greater than 5%.

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“…It was observed that the more negatively charged antibody layer would p-dope the graphene layer further, resulting in a larger I SD at V G = 0, whereas the positively charged BoNT layer caused a I SD drop at V G = 0 due to ndoping caused by the electrostatic gating effect. This GFET biosensor was able to show a normalized current change of 7% caused by the antibody-BoNT binding regime, an improvement from the 1% response demonstrated previously for AlGaN/GaN electrical sensors (Kim et al, 2017).…”

“…A primary motivator for using graphene in biosensing platforms is the simplicity in chemical functionalization (Novoselov et al, 2012). A variety of bioreceptors can be added to the surface of graphene which bind selectively to target analytes; aptamers (Xu et al, 2019), antibodies (Kim et al, 2017) and DNA (Liu et al, 2018b) are some examples of the bioreceptors used to functionalize the surface of graphene field effect transistors (GFETs) biosensors. Bi-functional molecules such as 1-pyrenebutyric acid N-hydroxysuccinimide ester (PBASE) can be used to facilitate the non-covalent functionalization of graphene at the pyrene end and the immobilization of bioreceptors at the N-hydroxysuccinimide ester end (Chen et al, 2001).…”

“…Bi-functional molecules such as 1-pyrenebutyric acid N-hydroxysuccinimide ester (PBASE) can be used to facilitate the non-covalent functionalization of graphene at the pyrene end and the immobilization of bioreceptors at the N-hydroxysuccinimide ester end (Chen et al, 2001). Covalent binding strategies, which introduce defects to the graphene lattice, can encourage the absorption of molecules onto the graphene surface thus reducing the specificity of the sensing device and so are avoided (Kim et al, 2017, Ohno et al, 2010.…”

“…Botulinum neurotoxin (BoNT) was the target analyte of choice for Kim et al, who deployed a back-gated GFET to detect this toxic protein, responsible for causing fatal muscle paralysis (Kim et al, 2017). This device relies on antibody-antigen binding events to detect BoNT at a concentration of 1 µM.…”

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“…101) Kim et al reported that a graphene-based device could be used to detect the molecular absorption of botulinum neurotoxin that consists of approximately 150k base-pair (bp) proteins. 102) With the immobilization of linkers of antibody-antigen binding sites on the graphene transistor, the electrical conductance of the transistor was modified by the adsorption of antibody proteins. 102) Fig.…”