Development of Nanomaterial-Based Electrochemical Sensors

Nowadays an increasing variety of sensors has significant impacts on our daily life. Simplicity, real-time monitoring, and minimal costs are the main issues to take into consideration toward the integration of sensing platforms. In light of these factors, electrochemical sensors are the most promising candidate technologies because of their easy-to-operate, rapid response, portability, and low cost. Due to remarkable advancements in nanotechnology, nanomaterials have facilitated the way for the fabrication of high-performance electrochemical sensing devices for various fields including environmental safety and medical diagnostics. Despite the attractive advantages that nanomaterial-based electrochemical sensors/biosensors can offer, there are still some challenges that need to be addressed in their design. Three main challenges, which are essential to be addressed in transferring lab-based research into field-based sensors, are fixed dynamic range, overlapping signals in the complex samples, and low sensitivity.
This thesis presents the development of nanomaterials based electrochemical sensors/biosensors towards applications in environmental analysis and medical diagnostics by addressing these current challenges in the practical application of electrochemical sensors/ biosensors. We developed a sensitive electrochemical aptasensor for label-free detection of lactoferrin as a biomarker for urinary tract infection (UTI) by immobilizing a novel multivalent aptamer on the surface of screen-printed gold electrodes (SPGEs). Introducing the multivalent aptamer as the bioreceptor with high affinity and good specificity against human lactoferrin helped to enhance the electrochemical signals and widen the working window. Due to its excellent sensitivity, wide linear range, simple sensing procedure, and fast response, this electrochemical aptasensor has a great potential for the development of a new sensing device for the early diagnosis of UTI.
To overcome overlapping electrochemical signals, an electrochemical sensor was developed based on screen-printed carbon electrodes (SPCEs) modified with butterfly-shaped silver nanostructure (AgNS) for concurrent detection of four heavy metals in water samples. The presence of AgNPs helped to improve the stability, sensitivity, and reliability of SPCEs and provide four distinguish signals for a mixture of four heavy metals sample. This electrochemical sensor with an excellent degree of robustness, high reproducibility, simple sensing procedure, and fast response has a great potential for on-site water quality monitoring.
Moreover, to increase the sensitivity and reproducibility of the electrochemical immunosensor, we designed a sandwich-type electrochemical immunosensor for detection of a cancer biomarker using an internal bio-redox reporter. Carcinoembryonic antigen (CEA) was selected as a target of interest in this work because of its wide usage in the diagnosis, staging, monitoring, and prognosis of cancers. The sandwich-type electrochemical immunosensor based on the internal bio-redox reporter enjoys the excellent potential for the development of CEA monitoring due to its fast response, simple fabrication, and user-friendly protocols.