A pyridoxal based bio-compatible fluorometric chemosensor for recognition of Zn2+ ions: Theoretical approaches and application in live cell imaging

A simple pyridoxal-based chemosensor (HL = 4-(((furan-2-ylmethyl)imino)methyl)-5-(hydroxymethyl)-2-methylpyridin-3-ol) was synthesized which selectively detects Zn2+ ion in HEPES buffer at pH = 7.4 (MeOH:H2O, 9:1, (v/v)) among other competitive metal ions. Around 10-fold increase in fluorescence intensity was seen at 472 nm after excition at 390 nm. HL displays blue fluorescence with a large stoke′s shift (∼80 nm) in presence of Zn2+ ion. A 1:1 binding stoichiometry between HL and metal ions (Zn2+) and the PET-OFF-CHEF-ON mechanism had been established by different spectroscopic techniques and theoretical studies. Low LOD value of the chemosensor towards Zn2+ (lower than the WHO's guideline of 76.5 µM) and strong binding constant (K = 1.54 × 105 M−1) suggest the applicability of HL towards biological cell imaging studies under physiological conditions. MTT assay was carried out to evaluate the toxicity of probe HL up to maximum concentrations with PC3 cell line.