Label-free and intelligent fluorometric array for simultaneously sensing of multiplexed metal ions based on DNA conformational diversity.

Multiplex detection of metal ions is often challenged by their similar charge states and ionic radii, which interfere with for simultaneous analysis and cause the low selectivity of conventional lock-and-key recognition elements. Herein, a label-free and intelligent fluorometric array has been developed for simultaneously probing multiplexed metal ions by utilizing the conformational diversity of DNA structures, including G-triplex, G-quadruplex, and dimeric G-quadruplex DNA. The sensing mechanism relies on thioflavin T intercalation, which converts metal-binding-induced DNA conformational changes into quantifiable fluorescence signals. The resulting fluorescence fingerprints were first visualized using principal component analysis and subsequently classified using supervised machine-learning algorithms. A comparative evaluation of multiple models reveals that the support vector machine achieves the highest classification performance for selective identification of multiple metal ions. The developed fluorometric array can accurately distinguish the samples containing various metal species (Fe3+, Co2+, Hg2+, Ni2+, Zr4+, Ag+, and Zn2+) over a wide range of concentrations (10-200 μM), with a 100% accuracy in blind validation tests. Subsequently, the feasibility of the array for detecting multiple metal ions in mixtures, as well as in lake water and tap water, is also demonstrated. As compared with most current analysis technologies, this method offers the desirable advantage of simultaneous discrimination of multiple metal ions including the heavy and non-heavy ones. Therefore, this study establishes a powerful, efficient, and cost-effective platform for the simultaneous and intelligent detection of multiple metal ions, showing strong potential as a rapid on-site screening tool for preliminary risk assessment of metal contamination.