Portable Smartphone Platform Integrated with a Nanoprobe-Based Fluorescent Paper Strip: Visual Monitoring of Glutathione in Human Serum for Health Prognosis

The glutathione (GSH) level in human serum is closely associated with several life-threatening diseases, and tracing the aberrant GSH level can monitor the subhealth conditions at an early stage for human health prognosis. Developing portable and direct read-out mini-devices is an inevitable trend for reliable point-of-care (POC) detection of GSH in real-time/on-site conditions. We herein report a portable smartphone-sensing platform, a ratiometric fluorescence sensor combined with the 3D-printed smartphone device for rapid, sensitive, quantitative, and on-the-spot determination of GSH in human serum. The powerful fluorescence "off-on" nanoprobe was constructed by mixing the blue carbon dots (CDs) and orange gold nanoclusters (AuNCs) with the assistance of copper ions. The quenched fluorescence can be quickly restored upon interacting with GSH, showing a distinct color variation from blue to purple to orange. Integrated with the paper strip printed by the probe ink, the smartphone platform installed with a Color Recognizer App could accomplish sensitive, reliable, and real-time/on-site detection of GSH in human serum, which shows great significance for early disease diagnosis. The constructed smartphone platform is expected to develop into portable home medical equipment to realize convenient and rapid preliminary monitoring and self-assessment of health.