A hybrid fluorescent probe for the selective detection of divalent Hg²⁺ and trivalent Al³⁺ ions and their biological applications

Metals are extensively used for different applications in agriculture and industry. Accumulations of these metals in the environment lead to serious health concerns. Currently, fast and accurate detection of metal ions in the environment or biological system has become a critical issue. Hence, developing an appropriate tool for the detection of metals can help reduce environmental metal pollution and reduce health concerns. In the present study, a hybrid fluorescent probe or chemosensor for parallelly detecting two important metal ions (Mercury and Aluminium) has been designed and tested for its detection efficiency. The newly synthesized chemosensor 3′,6′-bis(ethylamino)-2′,7′-dimethyl-3H-spiro[isobenzofuran-1,9′-xanthen]-3-one (RS) was found to specifically detect Hg²⁺ and Al³⁺ ions with high sensitivity and selectivity. The chemical and physical properties of chemosensor RS were tested using single-crystal X-ray diffraction, UV and Fluorescence analysis. The quick response to Hg²⁺ and Al³⁺ is attributable to the creation of a coordinate bond present between the chemosensor RS and the metal ion. The selective sensing of chemosensor RS is due to the spirolactam ring opening followed by the development of proper coordinate geometry in the chemosensor. ¹H NMR titration experiment and Job's approach studies suggest a significant binding stoichiometry between the chemosensor RS and the metal ions at a 1:1 ratio. The limit of detection (LOD) of chemosensor RS was determined to be 1.88 µM for Al³⁺ and 1.75 µM for Hg²⁺ ions. The in vivo studies using two experimental animal models, Drosophila melanogaster (fruit fly) and Poecilia reticulate (guppy fish), clearly demonstrate its efficiency in detecting endogenously absorbed Hg²⁺ and Al³⁺. Thus, chemosensor RS can selectively and simultaneously detect Hg²⁺ and Al³⁺ in biological or environmental samples and can help us in monitoring metal leaching into the environment.