Electrical label-free sensing of cardiac troponin biomarker: FET-based integration with substrate-gate coupling
Acute myocardial infarction (AMI) is a leading cause of death worldwide despite the existence of therapy’s advances. Therefore, an early diagnosis method by using cardiac biomarkers is essential to enable correct countermeasures. Cardiac Troponin I (cTnI) is one of the cardiac biomarkers for early d...
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| Format: | Thesis |
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| Language: | English |
| Subjects: | |
| Online Access: | http://dspace.unimap.edu.my:80/xmlui/bitstream/123456789/77989/1/Page%201-24.pdf http://dspace.unimap.edu.my:80/xmlui/bitstream/123456789/77989/2/Full%20text.pdf http://dspace.unimap.edu.my:80/xmlui/bitstream/123456789/77989/4/Mohamad%20Faris.pdf |
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| Summary: | Acute myocardial infarction (AMI) is a leading cause of death worldwide despite the existence of therapy’s advances. Therefore, an early diagnosis method by using cardiac biomarkers is essential to enable correct countermeasures. Cardiac Troponin I (cTnI) is one of the cardiac biomarkers for early diagnosis of AMI and considered as ‘gold standard’ for cardiac muscle injury determination. The detection of cTnI through an electrical-based biosensor allows label-free detection by converting biomolecular binding event into a significant electrical signal via a semiconductor transducer. It utilizes
conductivity to specify the existence of biomolecules. One of the electrical-based
biosensors known as field-effect transistor (FET)-based biosensor has drawn much
attention for owning the concept of charge transduction; thus, allows early, high
sensitivity, high selectivity, and rapid diagnosis of the specific cardiac biomarker at low
concentrations. In this work, the zinc oxide (ZnO)-FET biosensor coupled with substrategate
has been designed and fabricated for the detection of cTnI biomarker. ZnO thin film,
as n-type biocompatible semiconductor material, and also as transducer was deposited via
sol-gel and spin coating techniques between p-type source and drain terminal on SOI
substrate, forming a p-n-p junction, a device capable of bio-sensing application. The
surface morphology of the thin film was characterized by using atomic force microscopy
(AFM) and field emission scanning electron microscopy (FESEM). The thin film, which
demonstrated hexagonal wurtzite phase as shown by X-ray diffraction (XRD) analysis
appropriate for biomolecules interaction. The surface of the ZnO thin film was
immobilized with cTnI monoclonal antibody (MAb-cTnI) as biological receptor via
covalent binding technique for capturing cTnI biomarker. The process was validated by
Fourier transform-infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). The
device structure was simulated in Silvaco Atlas 2D-simulator, to elucidate its electrical
characteristic, by means of hole and electron concentration in the channel and buried
oxide/substrate interface, respectively. The device demonstrated a new strategy via
electrical characterization with the introduction of substrate-gate coupling that enhanced
the formation of hole conduction layer at the channel between drain and source region.
Finally, the biosensor shown significant increment in relative changes of drain current
level in a linear range of 6.2 to 16.5 % with the increase of positively charge cTnI
biomarker concentrations from 1 ng/ml to 10 μg/ml. The device sensitivity of the
detection is at 2.51 %·(g/ml)-1 with limit of detection (LOD) down to 3.24 pg/ml. |
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