Screening arsenic(III)-binding peptide for colorimetric detection of arsenic(III) based on the peptide induced aggregation of gold nanoparticles.

A suitable As(III)-binding ligand is the key to realize selective and sensitive As(III) sensing. In this study, phage display technique was used for the screening of As(III)-binding peptide. By negative screening against some representative metal cations and positive screening against target As(III), phages that bind to foreign metal cations were eliminated, while those bearing As(III)-binding peptides were kept and enriched. After DNA sequencing and phage ELISA analysis, 5 sets of As(III)-binding peptides were identified, with high content of N-containing functional groups as their predominate feature. A highly specific peptide (sequence: T-Q-S-Y-K-H-G) with the highest frequency of occurrence and best selectivity for As(III) was finally chosen. This peptide with a cysteine added at the C-terminal induces the aggregation of gold nanoparticles (AuNPs), whereas the competitive binding of As(III) to the peptide prevents the aggregation of AuNPs. Based on this observation, a simple and sensitive colorimetric sensing assay was developed, with a limit of detection (LOD) of 54nM (4μgL-1) for As(III). The As(III) sensor showed high selectivity over other metal ions including As(V), and was validated by As(III) analysis in certified reference material and environmental water samples.