Paper-Based Fast-Flow Electrochemical Device Enabling Self-Calibrated and High-Throughput NADPH Measurements

Microfluidic paper-based electrochemical devices (μPEDs) are transforming cost-effective and portable diagnostics. However, conventional μPEDs are limited to a single use, as the removal of analyzed solutions is challenging, preventing repeatable measurements. This study introduces a paper-based fast-flow electrochemical device (PFED) design that overcomes this limitation, enabling multiple detections within a single device without requiring external power. Unlike traditional μPEDs, the PFED integrates a plastic hollow channel with a wax-printed channel, ensuring that fluid flow is not solely dependent on capillary action. This enhanced configuration accelerates liquid transport, facilitates rapid solution exchange, and significantly improves device repeatability. Additionally, the PFED, coupled with a copper phthalocyanine-modified screen-printed graphene electrode (CuPc/SPGE), introduces a novel electrochemical sensing strategy for NADPH detection. Under optimized conditions, the sensor achieved a detection limit of 3.75 μM and a limit of quantitation of 12.5 μM. The integration of a fast-flow platform with electrochemical detection not only enables repeatable and automated measurements but also provides superior self-calibration capabilities. Finally, the PFED was successfully applied to G6PD deficiency assessment, where NADPH monitoring enabled the differentiation of healthy and deficient enzyme variants. These advancements position the PFED as a highly versatile and efficient tool for diverse analytical applications.