Stackable Lab-on-Paper Device with All-in-One Au Electrode for High-Efficiency Photoelectrochemical Cyto-Sensing

Highly conductive, robust, and multifunctional integrated paper-supported electrodes are requisite to fulfill the promise of paper-based analytical application. Herein, an all-in-one Au electrode comprising of detection zone, waterproof electronic bridge, and signal output contactor was engineered via combining the double-sided growth method with the secondary wax-printing. Benefiting from the strongly omnidirectional conductivity and desirably mechanical robustness of the as-prepared electrode, a stackable lab-on-paper cyto-device integrated with high-efficiency photoelectrochemical strategy was developed for the MCF-7 cells assay. Specifically, the detection zone of the electrode, serving as the signal generator, was functionalized with a low-toxic cosensitized structure composed of corn-like ZnO nanorods, graphene quantum dots (GQDs), and Ag₂Se QDs. With the proximity control of DNA hairpin-based aptamer probe (DHAP), a strong photocurrent could be promoted by the activated cosensitization effect and collected on the signal output contactor via the electron transport of waterproof electronic bridge. Upon the MCF-7 cells recognition, the DHAP switched from closed to open state with the formation of DNA-cell bioconjugates and the spatial separation of Ag₂Se QDs linked on the terminal of DHAP from the electrode surface. The photocurrent was noticeably decreased due to the double inhibition of steric hindrance effect and vanished cosensitization effect. Based on the target-triggered photocurrent attenuation, the sensitive detection of target cells was achieved. This work not only provided a unique method for paper-based electrode preparation but also offered a powerful platform for the highly sensitive photoelectrochemical bioanalysis.