Simple, rapid and label-free colorimetric assay for arsenic based on unmodified gold nanoparticles and a phytochelatin-like peptide

In this paper, we report a simple, rapid and selective colorimetric visualization of arsenic using unmodified gold nanoparticles (AuNPs) and a phytochelatin-like peptide (gamma-Glu-Cys)(3)-Gly-Arg (denoted as PC3R). Arsenic prevented the peptide from attaching to the surface of AuNPs by coordinating to all the three cysteine residues of PC3R, thus preventing the PC3R-triggered AuNPs aggregation and color change. The present approach is selective to arsenic detection and is much faster and simpler than the conventional analytical methods. The detection limit is 20 nM, which is lower than the World Health Organization's (WHO) standard for drinking water. The feasibility for the detection of arsenic in groundwater has also been demonstrated. This method will be valuable for the design of new types of metal ions sensors and will likely lead to many colorimetric detection applications in environmental monitoring.