Human peripheral blood mononuclear cells targeted multidimensional switch for selective detection of HSO₃⁻ anion

A new ratiometric π-conjugated luminophore with donor-acceptor (D- π- A) network CM {(E)-2-(4-(2-(9-butyl-9H-carbazol-3-yl)vinyl)benzylidine)malononitrile} has been synthesized by malononitrile conjugated carbazole dye with an intervening p-styryl spacer. Here, p-styryl conjugated malononitrile is used as a recognition site for the detection of HSO₃⁻ with a fast response time (within 50 s). In a mixed aqueous solution, CM reacts with HSO₃⁻ to give a new product 1-(9-butyl-9H-carbazol-3-yl)-2-(4-(2, 2-dicyanovinyl)phenyl)ethane-1-sulfonic acid. The probe exhibits positive solvatofluorochromism with solid state red fluorescence. The restriction of intermolecular rotation of p-styryl conjugated malononitrile unit enhances the typical solid state fluorescence properties. The probe (CM and its corresponding aldehyde CA) also demonstrates a strong solvent dependence yielding blue to green to pink and even red fluorescence in commonly used organic solvents like n-hexane, toluene, diethyl ether (DEE), THF, DCM, Dioxane, CH₃CN and MeOH. The chemodosimetric approach of HSO₃⁻ selectively takes place at the olefinic carbon exhibiting a prominent chromogenic as well as ratiometric fluorescence change with a 147 nm blue-shift in the fluorescence spectrum. CM can detect HSO₃⁻ as low as 1.21 × 10⁻⁸ M. Moreover, the CM can be successfully applied to detect intrinsically generated intracellular HSO₃⁻ in human peripheral blood mononuclear cells (PBMCs). CM has shown sharp intensities (2628 ± 511.8) when the cells are HSO₃⁻ untreated. At green channel (at 486 nm) almost negligible fluorescence intensities are found (423 ± 127.5) for HSO₃⁻ untreated samples. However, the green fluorescence (2863 ± 427.5) increases significantly (p < 0.05), and simultaneously the red fluorescence gets significantly (p < 0.05) diminished (515 ± 113.2) after addition of HSO₃⁻. The CM has been effectively utilized for evaluating the bisulfite ions in food samples as well. The concentrations of HSO₃⁻ in diluted sugar samples have been determined with the recovery of 97.6–9.12%.