Developing a Colorimetric, Magnetically Separable Sensor for the Capture and Detection of Biomarkers
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Point-of-care testing (POCT) devices have received increasing attention because of their potential to address the urgent need for quick and accurate diagnostic tools, especially in areas of personal care and clinical medicine. They offer several benefits over current diagnostic systems, including rapid diagnostic results in comparison to microbial cultures, simple interpretation of results, portability, and requiring no specialised laboratory equipment or technical training to operate. These are essential for diagnosing critical illnesses, such as sepsis, in areas of poor healthcare infrastructure. Sepsis, an innate physiological response to infection, is a growing problem worldwide with high associated costs and mortality rates, and affects a wide range of patients including neonates, infants, the elderly, and immunocompromised individuals. A literature review of the biomarkers of sepsis and the currently available diagnostic systems indicates the need for a biosensor capable of meeting the requirements of designing POCT systems and achieving detection of low concentrations of biomarkers. To meet these demands, two significant contributions to developing POCT platforms have been achieved and described in this thesis, including: 1) development of a colorimetric, magnetically separable biosensor that can be easily fabricated and demonstrates an easily identifiable colour response upon analyte detection, as well as the ability to capture and detection target biomarkers at low concentrations from complex solutions; and 2) tuning of the biosensor’s colorimetric response to achieve low detection limits, as well as demonstration of the versatility of the biosensor for sensing different target analytes. The developed biosensor in this work combines colour responsive polydiacetylenes and superparamagnetic iron oxide for the first time to achieve a biosensor capable of meeting these demands. The sensors exhibit identifiable colour responses to biomolecule detection, capture of a target analyte from complex solutions, sensing of different target analytes, a lower detection limit of 0.01 mg/mL, and rapid separation from solution with a common magnet. This work has been a significant demonstration of the capabilities of this biosensor as a new platform for POCT systems to diagnosis sepsis, and potentially other sensing applications.