Graphene FET Sensors for Alzheimer’s Disease Protein Biomarker Clusterin Detection

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.

Rapid Biomarker Screening of Alzheimer’s Disease by Interpretable Machine Learning and Graphene-Assisted Raman Spectroscopy

“…Studying biomarkers related to AD greatly accelerates the understanding of the disease and can lead to new treatments against dementia. , Three biomarkers, T-tau, P-tau, and Aβ 42 , have been identified and confirmed in the cerebrospinal fluid that are strongly associated with AD and could be used as progression markers in developing drugs . To detect the AD-associated biomarkers in the brain, various imaging techniques have been developed, such as magnetic resonance imaging (MRI) and positron emission tomography (PET). − However, MRI and PET are costly and time-consuming while they still lack specific molecular information. , Other biosensing methods such as surface plasmon resonance biosensors and field-effect transistors offer specific information on the optical or electronic properties of the analyte − and, thus, are insufficient to gain comprehensive insights into the biomarkers of AD. Recently, spectroscopy based detection of AD biomarkers via immunoassay and fluorescence on blood and cerebrospinal fluid (CSF) has been intensively investigated in preclinical stages, − but they are not label-free, which prevents the discovery of novel biomarkers.…”

Detection of Glial Fibrillary Acidic Protein in Patient Plasma Using On-Chip Graphene Field-Effect Biosensors, in Comparison with ELISA and Single-Molecule Array

“…Furthermore, GFET biosensors consume very low amounts of power and have great potential for mass production. GFET biosensors have been utilized for ultralow detection of a variety of biological species including proteins, exosomes, DNAs, viruses, and other disease biomarkers. − However, so far, there is no report of the detection of GFAP in patient samples for neurological diseases using the GFET technology. Here, we recruited six patients with moderate–severe TBI (defined by the Mayo classification), and we demonstrated an on-chip GFET biosensing platform for ultrasensitive and ultrafast detection of GFAP with the LOD down to 20 fg/mL (400 aM) in clean phosphate-buffered saline (PBS) and 231 fg/mL (4 fM) in patient plasma.…”

Colorimetric Aptasensor for the Visual and Microplate Determination of Clusterin in Human Urine Based on Aggregation Characteristics of Gold Nanoparticles

“…For the detection of clusterin, quantitative immunoprecipitation liquid chromatography/mass spectrometry (IP-LC/MS) for urine samples of cynomolgus and enzyme-linked immunosorbent assay (ELISA) analysis for nasal secretion samples of humans have been reported. , The biggest challenge these classical methods face is that the sensitivity is not high enough and the operation is not simple and fast enough. With the development of nanotechnology and sensing technology, the emergence of biosensors makes it possible to make up for the defects of traditional methods. − Label-free immunosensors that depend on electrochemistry and graphene field-effect transistor biosensors for clusterin have been developed. , The essence of these sensors is the signal amplification system based on the antigen–antibody recognition reaction, so the sensitivity of detection is significantly improved. In addition to the signal amplification system, improving the recognition response elements of target molecules is another way to build clusterin biosensors that meet the needs of clinical testing.…”