Simultaneous detection of trace Hg2+ and Ag+ by SERS aptasensor based on a novel cascade amplification in environmental water

Mercury ions and silver ions will be doped in environment during the entire process of water circulation, which is harmful to ecological balance and human body. Surface Enhanced Raman Scattering (SERS) acts as an effective method in detecting heavy metal ions, due to its easy processing, rapid detection, and fingerprint identification. At present, it is still a challenge to simultaneously detect multiple heavy metal ions based on SERS sensor. Herein, we developed a new SERS aptasensor, applying cascade nucleic acid amplification strategy to detect Hg2+ and Ag+, which greatly improved the sensitivity. Meanwhile, the use of aptamers can transform the concentrations of Hg2+ and Ag+ into DNA signal. And thymine-Hg2+-thymine and cytosine-Ag+-cytosine pairs were formed to simultaneously identify Hg2+ and Ag+. Multiple analytical strategy of this SERS aptasensor can not only avoid the inconvenience caused by different techniques or experiment conditions, but also reduce cost, time, and difficulty. In consequence, we obtained a lower detection limitation (LOD Hg2+=4.40 aM, LOD Ag+=9.97 aM) in the linear range of 0.2–125 fM. The results demonstrate that this SERS aptasensor is capable of being widely applied to simultaneously detect multiple heavy metal ions or other toxic substance in environmental water.