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UBC Theses and Dissertations

Development of a UV-induced metal-oxide chemiresistive biosensor for lactate monitoring Taleghani, Nastaran


Determining the concentration of biomarkers offers insights into the health condition and performance of the body. The vast majority of biosensors applied to measuring biomarkers in biological fluids are electrochemical bases; however, these biosensors suffer from several key drawbacks, thus preventing their widespread applications. These include the need to utilize complex sensing materials to obtain desirable analytical performance, which prevents their practical application, and to operate at a relatively high potential, which leads to inaccurate measurements due to the undesired oxidation of non-target molecules. A novel photo-induced chemiresistive biosensor is introduced here that addresses these challenges. A UV-induced ZnO nanorod chemiresistive biosensor was developed and applied to lactate monitoring in sweat as a model biomarker. The detection mechanism of lactate based on its interaction with ZnO nanorods was proposed. Furthermore, the effect of electrode design and operating parameters, including irradiance, radiation wavelength, and applied potential, were evaluated. The highest response, the shortest response time, and complete recovery were obtained at 5.6 mW/cm² irradiance of 365 nm and 0.1 V applied potential. The results indicated that the developed transduction platform utilizing a simple sensing layer is a promising technique with excellent analytical performance for detecting biomarkers. The selectivity challenge of the UV-induced ZnO nanorod chemiresistive biosensor was addressed by immobilizing lactate oxidase on the ZnO nanorods. The sensor exhibited excellent lactate monitoring capability within the dynamic range expected in the sweat. The appropriate amount of enzyme load of 10 units was found to provide the desired analytical performance. Further, the biosensor showed superb selectivity with responses of 1% or less of the lactate signal when exposed to interfering molecules, indicating its potential for analyzing the target iv biomarker in biological samples. Furthermore, the biosensor exhibited high reproducibility with a relative standard deviation of less than 2% and long-term storage stability (91% after five weeks), highlighting its potential for practical purposes. The overall results indicated the potential of this transduction platform as a promising technique with excellent analytical performance for detecting biomarkers, thereby paving the path toward the emergence of photo-induced chemiresistive biosensors for real-life applications.

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