Ultrasensitive aptamer biosensor for arsenic (III) detection based on label-free triple-helix molecular switch and fluorescence sensing platform.

Arsenic ion is a well-known harmful heavy element widely existing in the environment. Arsenic pollution occurring frequently has become increasing a serious worldwide threat to human health and the environment. The development of sensitive and reliable methods to detect As ³⁺ in water is of great importance to biochemical research and monitoring applications. Herein, a label-free fluorescence sensing platform was elaborately designed for As ³⁺ monitoring using exonuclease III (Exo III)-assisted cascade target recycling amplification strategy. The triple-helix molecular switch was employed as the sensing element and 2-amino-5,6,7-trimethyl-1,8-naphthyridine was used as the signal indicator. The resulting biosensor is simple, ultrasensitive, and exhibits a limit of detection of 5 ng/L with high selectivity. Meanwhile, the proposed sensor is successfully applied to determination of As ³⁺ in practical sample analysis (tap water, lake water and pond water). The results shown herein have important implications in the development of new fluorescent sensors for the fast, easy, and selective detection and quantification of As ³⁺ in water samples. More importantly, the proposed platform can be extended to detect other heavy metal ions with newly designed triple-helix molecular switch, as well as pesticide residue, antibiotic residues, and biomarkers by using aptamer sequences.
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