Graphene FET Sensors for Alzheimer's Disease Protein Biomarker Clusterin Detection.

Paul Davey,Jerome Charmet,Benjamin O’Driscoll,Samar Damiati,Carrie Haslam,Toby Whitley,Theodore Bungon,Shakil A Awan,Giuliano Siligardi

doi:10.3389/fmolb.2021.651232

Abstract

We report on the fabrication and characterisation of graphene field-effect transistor (GFET) biosensors for the detection of Clusterin, a prominent protein biomarker of Alzheimer’s disease (AD). The GFET sensors were fabricated on Si/SiO2 substrate using photolithographic patterning and metal lift-off techniques with evaporated chromium and sputtered gold contacts. Raman Spectroscopy was performed on the devices to determine the quality of the graphene. The GFETs were annealed to improve their performance before the channels were functionalized by immobilising the graphene surface with linker molecules and anti-Clusterin antibodies. Concentration of linker molecules was also independently verified by absorption spectroscopy using the highly collimated micro-beam light of Diamond B23 beamline. The detection was achieved through the binding reaction between the antibody and varying concentrations of Clusterin antigen from 1 to 100 pg/mL, as well as specificity tests using human chorionic gonadotropin (hCG), a glycoprotein risk biomarker of certain cancers. The GFETs were characterized using direct current (DC) 4-probe electrical resistance (4-PER) measurements, which demonstrated a limit of detection of the biosensors to be ∼ 300 fg/mL (4 fM). Comparison with back-gated Dirac voltage shifts with varying concentration of Clusterin show 4-PER measurements to be more accurate, at present, and point to a requirement for further optimisation of the fabrication processes for our next generation of GFET sensors. Thus, we have successfully fabricated a promising set of GFET biosensors for the detection of Clusterin protein biomarker. The developed GFET biosensors are entirely generic and also have the potential to be applied to a variety of other disease detection applications such as Parkinson’s, cancer, and cardiovascular.

Highlights

Graphene, a single atomic plane of carbon, was considered to be thermodynamically unstable until 17 years ago. Novoselov et al (2004) experimentally demonstrated that graphene can exist in the free state at room temperature, and that it is stable as a single layer of graphene making it a zero bandgap semiconductor
The graphene field-effect transistor (GFET) were characterised using Raman Spectroscopy to analyse the quality of the graphene channels (Ferrari et al, 2006) and with a semiconductor device parameter analyser to determine the electrical properties of the GFETs
We have reported the fabrication, functionalization, and characterization of graphene FET sensors using Raman spectroscopy, four-probe electrical measurements and absorbance spectra using the highly collimated microbeam of Diamond B23 beamline for the detection of a prominent Alzheimer’s disease (AD) protein biomarker, Clusterin

Summary

Introduction

A single atomic plane of carbon, was considered to be thermodynamically unstable until 17 years ago. Novoselov et al (2004) experimentally demonstrated that graphene can exist in the free state at room temperature, and that it is stable as a single layer of graphene making it a zero bandgap semiconductor. Graphene has the potential to advance many technological areas because of its outstanding material properties such as its high carrier mobility (Novoselov et al, 2004, 2005b; Bolotin et al, 2008; Morozov et al, 2008), current carrying capacity (Castro Neto et al, 2009), thermal conductivity (Balandin et al, 2008), optical properties (Blake et al, 2008), and mechanical stability (Booth et al, 2008) It is being researched for various applications such as high-speed electronics (Lin et al, 2010; Awan et al, 2016), optoelectronics (Bao and Loh, 2012), solar cells (Wang et al, 2008), energy storage (Wang et al, 2009), electromechanical resonators (Bunch et al, 2007), composites (Stankovich et al, 2006), and biosensors (Justino et al, 2017; Haslam et al, 2018; Vu and Chen, 2019). Such GFET biosensors are being researched extensively for early diagnosis of Alzheimer’s disease (AD) and for a variety of other diseases such as Parkinson’s, cancer and cardiovascular

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