One of the significant challenges in modern medicine is the early screening and detection of diseases, as this not only improves the chances of successful treatment and recovery for patients but also helps minimize the overall treatment cost. Therefore, there has been a growing effort to develop practical diagnostic tools to enable earlier screening and detection of diseases, ultimately leading to better health outcomes and more efficient use of healthcare resources. This thesis aims at exploring and developing cost-effective and user-friendly point-of-care (POC) electrochemical devices that can be employed to accurately diagnose diseases with high sensitivity and selectivity.

Interleukin-6 (IL-6) is a vital cytokine involved in the intricate network of cell signaling within the immune...[ Read more ]

One of the significant challenges in modern medicine is the early screening and detection of diseases, as this not only improves the chances of successful treatment and recovery for patients but also helps minimize the overall treatment cost. Therefore, there has been a growing effort to develop practical diagnostic tools to enable earlier screening and detection of diseases, ultimately leading to better health outcomes and more efficient use of healthcare resources. This thesis aims at exploring and developing cost-effective and user-friendly point-of-care (POC) electrochemical devices that can be employed to accurately diagnose diseases with high sensitivity and selectivity.

Interleukin-6 (IL-6) is a vital cytokine involved in the intricate network of cell signaling within the immune system. It plays a significant role in various physiological processes and immune responses. Evidence has shown a significant correlation between IL-6 and conditions such as rheumatoid arthritis (RA) and COVID-19. Therefore, a miniaturized electrochemical magnetoimmunosensor (EC-MIS) was demonstrated for detecting interleukin-6 (IL-6) in human serum. The main thrust of this work is the significant enhancement of the sensitivity performance by utilizing a hybrid of reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) chemically modified onto the surface of a fabricated microelectrode platform. Integrated with microfluidic and immunoassay, this prototypic EC-MIS achieved the highly specific detection of IL-6 in human serum with a linear range from 0.97 to 250 pg/mL and a limit of detection (LOD) of 0.41 pg/mL.

While this magnetoimmunosensor has demonstrated satisfactory results in IL-6 detection,it still faces challenges related to complex operation procedures and high costs. Thus, a cost-effective disposable immunosensor based on microfluidic paper-based electrochemical system to selectively, sensitively and quantitatively detect interleukin-6 (IL-6) for predicting the health status of COVID-19 patients was reported. The highlight of this assay is the design and construction of an origami microfluidic paper-based platform and its integration with AuNPs and PPy hydrogel (AuNPs/PPy/o-μPEIS), to amplify the signal for electrochemical readout. This immunosensor displayed excellent sensitivity and selectivity in quantitatively detecting cytokine in human serum with a dynamic range of 5 to 1000 pg/mL and a lower detection limit (LOD) of 0.65 pg/mL.

Alpha-fetoprotein (AFP), usually synthesized by the liver and yolk sac throughout fetal development, is a widely used serological biomarker in medical diagnostics. Notably, AFP plays a crucial role in detecting and monitoring specific cancers, with hepatocellular carcinoma (HCC) being the most prominent among them. As a result, a novel and user-friendly electrochemical lateral flow immunoassay (e-LFIA) test strip is introduced for the early diagnosis of liver cancer by detecting AFP. A sandwich-type nanosphere composed of Ag nanoshell-coated gold nanoparticles loaded onto dendritic mesoporous silica nanoparticles (AuNPs@Ag/DMSNs) was integrated with a lateral flow strip platform to achieve the signal amplification. Using a custom smartphone-based analytical device, we achieved quantitative detection of AFP with high sensitivity and selectivity.