Development of silicon on insulator based nanogap sensor for Escherichia Coli O157:H7 detection
Breakthrough in nanotechnology provides a great extent in biosensor development and application. Previous studies showed that nanogap sensor device provides excellent electrical behavior in sensing biomolecules samples. Nanogap sensor is a device having a pair of electrodes facing each other, whi...
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| Summary: | Breakthrough in nanotechnology provides a great extent in biosensor development and
application. Previous studies showed that nanogap sensor device provides excellent
electrical behavior in sensing biomolecules samples. Nanogap sensor is a device having
a pair of electrodes facing each other, which a molecule trapped in between its will be
identified by observing the electrical characterization. Conventional development
process requires prolonged and tedious compulsory additional method. Thus this
research project focus on developing various size of uniform nanogap structure in
nanometre scales which are capable of sensing Escherichia coli O157:H7 (E. coli
O157:H7) at a low concentration level. The development of the device was divided into
nanogap structure and gold pad structure process using electron beam lithography
(EBL) method and conventional photolithography method respectively. Silicon on
insulator (SOI) substrate was used to fabricate the nanogap structure and gold was used
as a gold pad for a probing purpose. The developed nanogap devices was physically
characterized by Field Emission Scanning Electron Microscopy and Scanning Electron
Microscope. Meanwhile, the performance of the devices was tested by evaluating the
capacitance and impedance reading by sweeping a frequency from 1M Hz to 0.1 Hz at
room temperature with 1.0 mV input using Dielectric Analyzer. The devices were tested
with de-ionized water and different pH level to optimize the sensor sensitivity that
related to the nanogap size. Prior to the detection of E. coli deoxyribonucleic acid
(DNA), the device was surface modified with NH2-Amine functionalized silane group
using 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde for DNA to be
covalently bonded with the APTES modified surface. The principle of the E. coli
detection is based on charge density changes of the DNA probe immobilization and
DNA target hybridization on the modified surface. The morphological testing results
shows that the developed devices were observed with 40, 80 and 100 nm nanogap size.
It was found that, the device with smallest gap size, 40 nm shows the highest sensitivity
and stability compared to the device with bigger gap size, 80 and 100 nm. In this project
40 nm size nanogap device was successfully developed as biosensor for E. coli O157:
H7 detection with capability to distinguish the impedance value between
complementary, non-complementary and single mismatch DNA sequences. In addition,
the device was able to detect E. coli O157: H7 DNA target at concentration limit from
10 nM to 1 pM with linear regression equation is ( ) = 3 × 10−7 + 5 × 10−9
and the correlation coefficient is 0.98. |
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