A Smartphone-Assisted Portable Strategy Based on Maple Leaf-Like Au/Cu2S/MoS2 Composite for Photothermal and Colorimetric Sensing of Cortisol

Herein, we describe a first-time synthesis of a maple leaf-like Au/Cu2S/MoS2 composite (denoted as ACM throughout this paper) with both photothermal and peroxidase (POD) activities. Based on the ACM, we devel-oped a smartphone-assisted portable detection platform for the photothermal and colorimetric dual-mode sensing of cortisol in human saliva. Because of complementary base pairing, the "Y"-type signal-probe (formed by the coincubation of ACM-DNA1 and ACM-DNA2) is fixed on cortisol-specific aptamer-functional-ized magnetic beads (MB-Aptcortisol). In the presence of target cortisol, MB-Aptcortisol is more likely to combine with cortisol, "Y"-type signal-probes are released, which can oxidize 3,3 ',5,5 '-tetramethylbenzidine (TMB) to blue oxTMB in the existence of H2O2. Notably, the oxTMB exhibits a distinct photothermal response which, in combination with the photothermal properties of the ACM, achieves transduction and signal amplification of cortisol through a cascade enzyme reaction. The photothermal and colorimetric signals increase with increasing target concentrations. This portable dual-signal sensing platform enables the detection of cortisol in the range of 5-10000 ng/mL, with detection limits of 0.11 and 0.25 ng/mL for photothermal and colorimetric signals, respectively (The reference concentration of cortisol in saliva of healthy people is 1-12 ng/mL in the morning and 0.1-3 ng/mL at night). It is inexpensive, user-friendly, and allows for rapid analysis, rendering it suitable for clinical applications.