Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

Multiplexed nucleic acid analysis using a linear-polyethyleneimine modified-zinc oxide photoelectrode Albert, Mitchell

Abstract

Biosensors are portable devices that can be used at the patient point-of-care to identify the presence, absence, and/or quantity of biomarkers, rapidly providing the user with important information regarding their health. However, commercially available devices at present are limited to monitoring physiological properties like heart rate or sleep quality, blood concentrations of compounds like glucose, or a single biomarker at a point in time (e.g., pregnancy or COVID-19 test). In contrast, a new, multiplexed biosensor could enable the identification of multiple targets, improving accuracy in the detection of diseases which may present with more than one distinctive biomarker. The photoelectrochemical (PEC) cell separates optical excitation from electrochemical signal generation, thus yielding a higher signal-to-noise ratio when compared to electrochemical or optical transduction methods, but much of the past research on PEC analysis of nucleic acids has required the use of external reagents or target-labelling steps. Zinc oxide nanoparticles are n-type semiconductors that are used in PEC applications due to their low manufacturing cost and green synthesis methods. However, they have a wide-band gap, and electron-hole recombination is rapid. Previous signal enhancement strategies for ZnO photoelectrodes have primarily employed costly bench-top synthesis procedures that would be difficult to scale. This thesis reports the development of a platform for photoelectrochemical analysis of single-stranded DNA (ssDNA), using a linear polyethyleneimine (LPEI) modified-zinc oxide photoelectrode. An increase in photocurrent was observed after LPEI modification. Two different nucleic acid capture probes were deposited onto the LPEI-ZnO photoelectrode for affinity-based ssDNA analysis via signal-off or signal-on transduction. The signal-off response is based on an increase in steric hinderance upon probe-target hybridization. The unique signal-on mechanism uses a partially hybridized double-stranded DNA probe labelled with a gold (Au) nanoparticle that selectively forms a heterojunction with ZnO via toehold displacement reaction in the presence of the target. Finally, the specificity of each assay was determined using a mismatched DNA target, which resulted in an insignificant signal change. Thus, this platform enables reagentless and multiplexed analysis of target DNA, paving the way towards scalable processing of biosensors for portable and rapid disease diagnoses.

Item Media

Item Citations and Data

Rights

Attribution-NonCommercial-NoDerivatives 4.0 International