Portable paper-based microfluidic devices with Cu_1-xAg_xS NPs modification for multiplex intelligent visualized...

Adrenaline and glucose are essential biomarkers in human body for maintaining metabolic balance. Abnormal levels of adrenaline and glucose are associated with various diseases. Therefore, it is important to design portable, on-site devices for rapid adrenaline and glucose analysis to safeguard health. Traditional paper-based analytical devices (μPADs) for multiplexed detection typically required multiple recognized probes, increasing the cost and complexity. Moreover, non-uniform color distribution, caused by lateral chromatographic elution effect, reduced results accuracy. Hence, it is necessary to construct visualized μPADs with controlled flow capability using single sensing probe for simultaneous adrenaline and glucose analysis in point-of-care testing (POCT).

The portable multiplexed 3D-folded μPADs have been developed for the visualized, accurate and simultaneous detection of adrenaline and glucose, employing Ag-doped copper sulfide nanoparticles (Cu_1-xAg_xS NPs) as multifunctional sensing probe. The μPADs integrated the sampling entrance layer, buffer layer and test layer into a single device through wax printing, allowing the analyte solution to flow vertically from buffer zones to detection zones, thereby minimizing lateral chromatographic elution effect. Cu_1-xAg_xS NPs, exhibiting laccase-like and peroxidase-like multi-enzyme activities, were modified on various detection zones of μPADs for multiplex colorimetric analysis of adrenaline and glucose. Based on Cu_1-xAg_xS-induced colorimetric reactions, the orange-red and blue colors were generated in adrenaline and glucose detection zones, respectively. Subsequently, color signals were converted into RGB values via smartphone application (APP) for rapid and intelligent results analysis. The Cu_1-xAg_xS-incorporated μPADs exhibited colorimetric uniformity and accuracy with limit of detection (LOD) of 10.2 nM and 11.5 μM, respectively.

The adjustable laccase-like and peroxidase-like activities of Cu_1-xAg_xS NPs induced by Ag doping provide a new perspective for multiple biomarkers analysis. Benefiting from the excellent multienzyme activity of Cu_1-xAg_xS NPs, μPADs can perform on-site, visual and multiplex analysis using a single probe, demonstrating their potential for POCT in personal healthcare. The 3D folded Cu_1-xAg_xS-incorporated μPADs with integrated horizontal and vertical flows exhibit uniform color signals for obtaining accurate detection results.