Dual-mode colorimetric determination of As(III) based on negatively-charged aptamer-mediated aggregation of positively-charged AuNPs

The aggregation and redispersion of positively-charged AuNPs ((+)AuNPs) modified with cysteamine (CS) could be regulated by the negatively charged As(III)-specific aptamer (As(III)-apt). In general, (+)AuNPs aggregated with increasing inducer concentration. However, in the present study, it was found that (+)AuNPs re-dispersed after a certain high concentration of As(III)-apt was reached. By optimizing the concentration of As(III)-apt that resulted in the aggregation and redispersion behavior of (+)AuNPs, a dual-mode colorimetric aptasensor for As(III) determination was established. It was not only able to quantify As(III) sensitively over a ranges of As(III) concentrations, but also to selectively differentiate As(III) and eliminate false results from other control ions by dual-mode. [Display omitted] Colorimetric determination of arsenic (As(III)) based on electrostatic attraction between positively-charged AuNPs and negatively-charged As(III) aptamer with bimodal responses (Mode D and Mode A). •The label-free As(III) aptamer decreases the detection cost.•The determination system only includes As(III) aptamer, positively-changed AuNPs and As(III).•False positives in specificity are avoided by the dual-mode signal outputs.