Dual-Label Sequentially Released DNA Probe for Self-Powered PEC-RGB Sensing of Coexisting Mycotoxins

Abstract On-site assay of multiple coexisting mycotoxins is critical for securing food safety and safeguarding public health. Photoelectrochemical (PEC) sensing meets the demand of on-site analysis owing to the advantages of easy miniaturization, rapid response, and low cost. However, existing signal discrimination strategies for multiplexed PEC detection typically rely on complex electrode modification and external instrumentation, limiting their on-site applicability. To address this issue, we developed a dual-label sequentially released DNA probe (DSRDP) and constructed an ion exchange-mediated modification-free self-powered sensing platform, which enables on-site PEC red-green-blue (RGB) sensing of dual targets. The DSRDP was formed by assembling Ag NPs-terminated double-stranded DNA and PC-Linker-modified hairpin DNA bearing CuO NPs on the magnetic beads’ surface. Upon the simultaneous recognition of two targets, the first signal label (Ag NPs) was obtained in the supernatant through magnetic separation, and the other signal label (CuO NPs) was released via UV-induced photocleavage of the photocleavable linker (PC-Linker). Subsequently, acidification of each signal label triggered the ion exchange (Ag+ or Cu2+) with the MgIn2S4 photoanode, which quenched the photocurrent resulting from the heterostructure formation. Meanwhile, Ag+ or Cu2+ also induced a color change of Na2S solution, which provided the visual RGB signal for the dual-target assay using a smartphone. The PEC-RGB sensor exhibited linear ranges of 1 fg/mL−100 ng/mL of aflatoxin B1 (AFB1) and ochratoxin A (OTA) with LODs of 0.24 fg/mL and 0.33 fg/mL in PEC mode, respectively, and linear ranges of 1 pg/mL−100 ng/mL of AFB1 and OTA with LODs of 10.96 fg/mL and 3.63 fg/mL in RGB mode, respectively. Featuring convenient target separation, rapid signal transduction, and self-powered detection, this work may pave the way for portable on-site detection of coexisting mycotoxins for food safety assessment and environmental monitoring.