Dual-modal flexible zinc-air battery-driven self-powered and impedimetric aptasensor based on the hybrid of V2CTx MXene and bimetallic layered double hydroxide for the detection of cortisol

Based on the heterojunction of V2CTx MXene and bimetallic CoNi-layered double hydroxide (CoNi-MLDH), a novel dual-modal electrochemical aptasensor (denoted as CoNi-MLDH@V2CTx) was developed for the noninvasive point-of-care detection of cortisol in different body fluids (such as sweat, urine, and blood). Herein, V2CTx nanosheets (NSs) were used as scaffolds for the in-situ growth of cobalt/nickel zeolitic imidazolate framework (CoNi-ZIF) polyhedrons, which was then converted to CoNi-MLDH NSs through an in situ etching–coprecipitating process. Benefiting from the merits of V2CTx NSs (excellent electrochemical activity) and CoNi-ZIF (large specific surface and pore size, rich functionality, excellent oxygen reduction, and strong bioaffinity toward aptamer), and from the synergistic effect, the CoNi-LDH@V2CTx junction showed great potential as a platform for the constructing the electrochemical aptasensor for detecting cortisol. Within a wide cortisol range 10 fg mL−1 to 100 ng mL−1, the dual-modal impedimetric and zinc-air battery-driven self-powered aptasensor based on CoNi-MLDH@V2CTx illustrated the ultralow detection limit of cortisol, 0.26 and 0.17 fg mL−1, respectively. They demonstrated high selectivity, superior stability, excellent reproducibility, and promising regeneration ability, and showed potential applications for cortisol analysis in different environments (sweat, urine, and blood). The present work provides a promising option for maintaining people’s mental health through the sensitive and selective detection of cortisol in human fluids.