Fingerprinting DNAzyme Cross-Reactivity for Pattern-Based Detection of Heavy Metals

Heavy metal contamination in food and water is a major public health concern because heavy metals are toxic in minute amounts. DNAzyme sensors are emerging as a promising tool for rapid onsite detection of heavy metals, which can aid in minimizing exposure. However, DNAzyme activity toward its target metal is not absolute and has cross-reactivity with similar metals, which is a major challenge in the wide-scale application of DNAzyme sensors for environmental monitoring. To address this, we constructed a four DNAzyme array (17E, GR-5, EtNA, and NaA43) and used a pattern-based readout to improve sensor accuracy. We measured cross-reactivity between three metal cofactors (Pb²⁺, Ca²⁺, and Na⁺) and common interferents (Mg²⁺, Zn²⁺, Mn²⁺, UO₂²⁺, Li⁺, K⁺, and Ag⁺) and then used t-SNE analysis to identify and quantify the metal ion. We further showed that this method can be used for distinguishing mixtures of metals and detecting Pb²⁺ in environmental soil samples at micromolar concentrations.