Dual-palindrome Chained Assembly Regulates the Formation of Palindromic DNAzyme Wire Transducers Empowering Sensitized and One-Step Copper Ion- Dependent Assay

The accurate and rapid analysis of heavy metal ions is significant for food safety and human health. In this work, a dual-palindrome chained assembly (dual-PCA) was rationally designed to form copper ion (Cu2+)-responsive palindromic DNAzyme wire (P-DNAzyme-W) transducers based on the inverted reading of palindromes. Structurally, P-DNAzyme-W is composed of numerous intermolecular paired dual-palindrome DNAzyme monomers. In the absence of Cu2+, the background fluorescence of the P-DNAzyme-W transducer was strongly quenched because of palindrome-induced co-quenching effects. Upon introduction of Cu2+ to form catalytic cores for the cleavage of the substrate strand into two parts, the sensing system exhibits strong fluorescence recovery within 25 min. These features allow the sensing system to exhibit a high signal-to-noise ratio to sensitized detect Cu2+ in one step but maximally maintain the simplicity of common DNAzyme monomers. Moreover, the sensing system possesses a good anti-matrix effect for sensitized detection of Cu2+ from lake water and tap water, suggesting promising potential in determining the level of Cu2+ in aquatic environments. We expect our research to provide an avenue to customize functional nucleic acids for heavy metal ion detection in the fields of food safety analysis, clinical diagnosis, and environmental monitoring.