Visually multiplexed quantitation of heavy metal ions in water using volumetric bar-chart chip.

Heavy metal ions monitoring in water is practically significant for the environment and the human health. In this work, a lab-on-a-chip biosensor was developed for multiplexed quantitation of heavy metal ions by the integration of triple-channel volumetric bar-chart chip with DNA-nanoparticle probes. This method possesses the capability for rapid detection of Cu2+, Pb2+ and Hg2+ simultaneously with high sensitivity, selectivity and accuracy. Due to the highly catalase-like activity of the urchin-like platinum nanoparticles, this sensor exhibits high sensitivity with the detection limits of 1.0 nM, 1.0 nM and 1.8 nM for sensing of Cu2+, Pb2+ and Hg2+ respectively, which are much lower than the requirement of the United States Environmental Protection Agency (EPA) in drink water and superior to the colorimetric method based on the metal ion-specific DNA assay. The accuracy and reliability were verified by our Atomic Absorption Spectrometry (AAS) and Atomic Fluorescence Spectroscopy (AFS) measurements of real water sample. As the results can be directly read out without the need of the external instruments or complicate data processing, this sensor is extremely practical for environmental applications.