RNA Mango-based sensors for lead

Lead (Pb²⁺) toxicity poses a serious threat to human health and remains a global concern; therefore, there is a critical need for the development of easy-to-use and cost-effective tools for the rapid monitoring of Pb²⁺. In this study, we demonstrate the potential of the RNA Mango aptamer as a sensitive and selective sensor for Pb²⁺. Our findings reveal that trace amounts of Pb²⁺ induce the formation of a G-quadruplex motif in RNA Mango, which facilitates dye binding and activates fluorescence. A detailed investigation of the fluorescence properties of RNA Mango with three different dyes, TO1-biotin, TO3-biotin, and thioflavin-T, in the presence of Pb²⁺ shows that RNA Mango has the highest binding affinity for Pb²⁺ in combination with TO1-biotin, with a <i>K</i>_D value as low as ∼100 nM. In the presence of Pb²⁺, RNA Mango has sub-micromolar affinity for all three dyes, showing the tightest binding to TO1-biotin (<i>K</i>_D ∼ 40 nM). Mango lead sensors detect low nanomolar concentrations of Pb²⁺ with limits of detection of 2-16 nM, which are significantly lower than its allowable limit in drinking water. RNA Mango exhibits remarkable selectivity toward Pb²⁺ and can detect Pb²⁺ in tap water samples. This work reports a new class of simple and inexpensive fluorescence-based sensors for lead and expands the repertoire of RNA-based lead sensors.