Design of Nanoscale Architectures for Miniaturised Electrochemical Biosensors

Abstract

Detecting diseases in their advanced stages leads to limited treatment choices and costly interventions that may or may not effectively slow down disease progression. Consequently, early-stage disease detection is pivotal, offering more treatment options and improved treatment outcomes while minimising costs. This approach also reduces the burden on patients and healthcare systems, enhancing overall quality of life and public health. In clinical settings, molecular diagnostic methods like polymerase chain reaction, enzyme-linked immunosorbent assay, and sequencing are employed for biomarker detection. Nevertheless, these techniques entail complex and time-intensive procedures, demanding sophisticated equipment and skilled personnel. Biosensors have emerged as a cost effective and sensitive tool for the detection of early-stage disease biomarkers. Amongst the various transduction mechanisms, electrochemical methods offer advantages of miniaturisation, portability, user-friendliness, easy signal processing, broad dynamic range, and lowest detection limits suggesting their potential for rapid implementation in clinical scenarios. Amongst various bio-receptors such as enzymes, antibodies, aptamers, and whole cells, aptamers offer high affinity and specificity, cost-effectiveness, stability, adaptability, reusability, lower risk of immunogenicity, and multiplexing capability to detection multiple biomarkers for early-stage disease detection and monitoring. Therefore, during my PhD I have developed aptamer-based electrochemical biosensors for the detection of various disease specific biomarkers ranging from proteins to miRNAs. By using an industry-relevant nanomaterial synthesis technique, flame spray pyrolysis (FSP), an efficient material platform for miniaturised electrochemical biosensor is achieved. These platforms enable the detection of disease-specific target biomarkers at attomolar concentrations, offering exceptional selectivity and the ability to customise the linear response range. For instance, we've successfully detected glycated albumin (GA), a crucial biomarker for diabetes management, at clinically relevant levels by attaching a selective DNA aptamer to the Au NIs surface. When appropriately passivated, these platforms demonstrate remarkable sensitivity and selectivity in mouse serum, highlighting their clinical potential. Furthermore, they exhibit adaptability in detecting various biomarkers, including miRNAs, insulin, and non-glycated human serum albumin (HSA). We've also assessed the platform's ability to determine the glycation ratio, which aids in better diabetes management. These findings offer a versatile material platform for scalable, cost-effective development of future portable and point-of-care biosensors. Another aspect of my work involves creating a simple yet highly sensitive and selective electrochemical biosensor architecture for rapid and portable miRNA detection. Existing miRNA biosensors typically require complex surface and probe modifications to achieve adequate sensitivity and selectivity. Focusing on miR-124, a relevant biomarker linked to retinal diseases, we've achieved a highly sensitive electrochemical biosensor with a detection range spanning 10^9 orders of magnitude. In contrast to most existing miRNA biosensors, we use a short capture probe along with dual surface passivation and equilibration strategy to prepare the biosensor surface before detecting the target miRNA. This approach ensures exceptional sensitivity, selectivity, and reproducibility while minimising interference from other miRNAs. These insights into engineering reliable and robust electrochemical surfaces for miRNA detection provide valuable guidance for designing compact miRNA sensing devices. Show more