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DC Field | Value | Language |
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dc.contributor.advisor | Soleymani, Leyla | - |
dc.contributor.author | Bakhshandeh, Fatemeh | - |
dc.date.accessioned | 2024-04-29T19:24:22Z | - |
dc.date.available | 2024-04-29T19:24:22Z | - |
dc.date.issued | 2024 | - |
dc.identifier.uri | http://hdl.handle.net/11375/29709 | - |
dc.description.abstract | The shifting landscape of global healthcare emphasizes the need for rapid biomolecular detection at the point of care. Electrochemical signal transduction has excellently met this demand, delivering biosensors characterized by high sensitivity and low detection limits. The latest version of these biosensors provides point-of-care diagnosis through wearable devices. Additionally, there is growing promise in photoelectrochemical biosensing. These systems integrate optical excitation to enhance electrochemical signal readout and offers enhanced sensitivity by decoupling signal input and output. For effective application of photoelectrochemical technology in point-of-care diagnostics improving photoelectrode stability, lowering detection limits, and enhancing signal transduction efficiency are crucial. To address these challenges, we first developed a photoactive material system by integrating TiO2 as the inorganic semiconductive nanomaterial and modifying it with an organic catecholate molecule, pyrocatechol violet, along with graphene quantum dots to make photoelectrodes with enhanced baseline photocurrent generation and heightened photo-absorption in the visible range. The resulting photoactive material system demonstrated enhanced colloidal stability and improved biofunctionalization capabilities. Then, leveraging the high binding affinity of catecholates on TiO2 incorporating additional functional groups for enhanced biofunctionalization, we designed a signal-on photoelectrochemical materials system by biofunctionalizing of the photoelectrode with aptamers as the bioreceptor to create a universal bacterial biosensor. This signal-on aptamer-based assay detected Escherichia coli in urine at a limit-of-detection of 1913 CFU/mL, meeting the acceptable thresholds for identifying urinary tract infections and urosepsis. Finally, our focus shifted to develop a novel materials system for continuous and in vivo wearable biosensing, utilizing a microneedle-based system integrated with an electrochemical sensor for real-time target analysis in interstitial fluid. Given the suitability of electrochemical readout for continuous in vivo biosensing, we chose it over the photoelectrochemical transduction method. However, this system still leveraged the flexibility and structure switching capabilities of aptamers used in photoelectrochemical sensing. The developed wearable biosensor combines ultrasensitive aptamer-based electrochemical measurements for in situ biomarker analysis with hydrogel microneedles. Our wearable device offers strong mechanical properties for efficient skin penetration. It also exhibits high sensitivity and specificity in detecting clinically relevant concentrations of glucose and lactate in vivo, validated in two different healthy and unhealthy animal models. This highlights the potential of the wearable sensor in altering personalized diabetes management methods. | en_US |
dc.title | Photoelectrochemical and Electrochemical Biosensing | en_US |
dc.title.alternative | Development of Materials Strategies for Improving the Performance of Electrochemical and Photoelectrochemical Biosensors | en_US |
dc.type | Thesis | en_US |
dc.contributor.department | Engineering Physics | en_US |
dc.description.degreetype | Thesis | en_US |
dc.description.degree | Candidate in Philosophy | en_US |
dc.description.layabstract | Biosensors have the potential to revolutionize healthcare, offering early diagnosis, disease prevention, and empowering patients with self-management tools. Biosensors combine biological components with physical or chemical transducers, allowing the detection or quantification of biological or chemical reactions by generating signals proportional to the analyte's concentration. Electrochemical transduction, a leading technique in biosensing, translates analyte concentration into measurable electrical signals. Despite its high sensitivity, portability, and capability for continuous monitoring, electrochemical transduction faces challenges related to background signals from applied electric potential. Photoelectrochemical system are making strides by separating signal readout from sensor excitation, overcoming the limitations of high applied potential in electrochemical system. In photoelectrochemical material systems, TiO2-based photoactive materials have gained significant attention; however, obtaining high photocurrents in the visible range remains challenging. Exploring TiO2 modification strategies in this thesis aims to amplify signals for effective signal-off photoelectrochemical biosensing. Building on this knowledge, along with the incorporation of aptamers, it was utilized to design signal-on photoelectrochemical materials systems. Although photoelectrochemical biosensors are powerful tools, electrochemical variants are better suited for wearable biosensors operating in in vivo conditions. The final objective of this thesis involves developing the Wearable Aptalyzer, a materials system that integrates biocompatible hydrogel microneedle arrays with an electrochemical aptamer-based biosensor for in vivo analyte monitoring. The resulting photoelectrochemical and electrochemical biosensors underwent extensive characterization, evaluating their analytical performance in terms of limit-of-detection, sensitivity, and specificity. | en_US |
Appears in Collections: | Open Access Dissertations and Theses |
Files in This Item:
File | Description | Size | Format | |
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Bakhshandeh_Fatemeh_202404_PhD.pdf | 4.33 MB | Adobe PDF | View/Open |
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