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Title: Development of hydrogel-based optical leaky waveguide biosensor for the detection of pathogenic bacteria
Author: Makhsin, Siti Rabizah
ISNI:       0000 0005 0290 2005
Awarding Body: University of Manchester
Current Institution: University of Manchester
Date of Award: 2019
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In this work, a hydrogel based optical leaky waveguide (OLW) biosensor was developed in order to detect biomolecules using changes in refractive index (Δn). Hydrogels formed from chitosan, agarose and acrylate were synthesised in order to be used as a waveguiding thin film in OLW biosensor. The concentration and thickness of the hydrogels defined by the spin coater speeds and time were optimised to produce a device chip with a single waveguide moded operation of OLW biosensor. For agarosechitosan hydrogel-based, the chip devices were fabricated for metal clad (MCLW) and dye clad (DCLW) format. The MCLW chip was fabricated using a titanium coated glass substrate on which the hydrogel layer was spin coated. The DCLW chip was assembled by adding a dye (Reactive Blue 4) into the hydrogel mixture before spin coating on a cleaned glass substrate. The hydrogel was crosslinked by adding glutaraldehyde just before the spin coating process. The acrylate-based polymer was successfully synthesised at 40% v/v PEGMEA-PEGDA and functionalised with 2.5%v/v NHS linker. The hydrogel was crosslinked using UV polymerisation method. For the performance of the fabricated device for detection of Δn of glycerol solution, the highest sensitivity of detection was obtained from acrylate-based MCLW chip with LOD: 2.22 x 10⁻⁶ RIU, while the optimum LOD of 2% w/v of chitosan-agarose hydrogel was measured at 4.28 x 10⁻⁶ RIU. The performance of the device to monitor the protein (bovine serum albumin; BSA and anti-BSA) interaction, the binding affinity in respect of change in peak angle (ΔΘ°) of chitosan matrix to the protein was measured at ΔΘ° ~ 0.0062 ± 0.0005°, while for acrylate-based hydrogel was obtained at ΔΘ° ~ 0.11 ± 0.013°. The MCLW chip made of hydrogel from acrylate-based was successfully immobilised with streptavidin and biotinylated anti-Streptococcus Aureus as a bioreceptor. Pathogenic bacteria; Streptococcus Aureus was detected with binding affinity measured at ΔΘ° ~ 0.089 ± 4.4 x 10⁻² °. The LOD was 9.53 x 10⁻⁷ RIU, which is equivalent to 143⁻¹ . The sensor specificity sensor was validated by non-binding observed for the bacteria: Escherichia coli tested in the active region of the sensor.
Supervisor: Gardner, Peter Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: refractive index changes ; label-free ; pathogenic bacteria detection ; optical leaky waveguide ; metal clad leaky waveguide ; Acrylate-based hydrogel ; optical biosensor