Label-free fluorescence detection of mercury(ii) and glutathione based on Hg2+-DNA complexes stimulating aggregation-induced emission of a tetraphenylethene derivative

Abstract

Herein, a sensitive and selective sensor for mercury(II) and glutathione based on the aggregation-induced emission (AIE) of a tetraphenylethene derivative stimulated by Hg²⁺-DNA complexes is reported. Aggregation complexes of AIE probes, quaternized tetraphenylethene salt and anti-Hg²⁺ aptamer ssDNA, were formed based on the electrostatic interactions between the ammonium cation of AIE probes and the backbone phosphate anions of DNA. In the presence of target Hg²⁺, the aptamer ssDNA with thymine (T)-rich sequences selectively bound with Hg²⁺ to form an Hg²⁺-bridged T base pair and the ssDNA changed into a hairpin-like structure. Therefore the AIE probing molecules were brought to be positioned closer. Accordingly, the conformational change of aptamer ssDNA resulted in an obvious enhancement in the fluorescence of the probing complex enabling the sensitive and selective detection of Hg²⁺. Furthermore, upon reaction of Hg²⁺ with biothiols, the compact structure was destroyed and the fluorescence decreased consequently. Sensitive detection of GSH was realised based on the decrease of fluorescence of the probing complex. The target-aptamer complexes stimulating aggregation-induced emission therefore show great promise for environmental and biological process monitoring and disease diagnosis.