SERS detection of mercury (II)/lead (II): A new class of DNA logic gates

A conceptually new class of DNA logic gates for Hg²⁺ and Pb²⁺ ion simultaneous detection has been constructed based on the activity of DNAzyme dependent on metal ions. For sensitive and specific detection of Hg²⁺ and Pb²⁺ ions, we demonstrate a surface-enhanced Raman scattering (SERS)-active platform by employing the oligonucleotide-functionalized and gold coated polystyrene microspheres (PSMPs). In this work, Hg²⁺ and Pb²⁺ were used as the input, and the SERS signals were the output. Hg²⁺ ions were captured by a mismatched T-Hg-T bridge. Pb²⁺ ions were bound to 8-17DNAzyme to break the cleavage substrate. The limit of detection (LOD) of Hg²⁺ is 0.1 nmol L^-1 and Pb²⁺ is 1.0 nmol L^-1, which is far below the limit of 10.0 ppb (31 nmol L^-1) and 10.0 ppm (3.02 × 10⁴ nmol L^-1) for drinking water stipulated by the World Health Organization. Additionally, this system has the potential to be ideal candidates for intelligent DNA calculator design applications. Furthermore, the designed strategy could be extended to other multiplex metal ions that can be combined with DNA molecules, and can be applied to many other fields such as environmental detection, toxin detection and liquid analysis.