Two novel pyrene-based Schiff base fluorescent probes for the turn-on detection of Zn2+and their application in bioimaging

Zinc is a trace element essential for maintaining human health, and zinc imbalance will lead to various diseases. Hence, it is imperative to design and construct fluorescent probes to effectively detect Zn2+ in organisms. In this study, two novel fluorescent probes, 1-((5-(pyrenyl)pyridine-2-imino)methyl)phenyl-2-ol (abbr. Py-Ph) and 1((5-(pyrenyl)pyridine-2-imino)methyl)naphthalene-2-ol (abbr. Py-Nap) were conceived and synthesized for the high-performance detection of Zn2+. Py-Ph and Py-Nap had low fluorescence background, large Stokes shifts (107 and 122 nm), and excellent photochemical stability in solutions. They undergo significant fluorescence enhancement and color change with existence of Zn2+ owing to the formation of 1:1 complex between the probes and Zn2+, which were characterized by job's plot, 1H NMR titrations, FTIR and HRMS, proving their turn-on and visual two-channel detection mode. In addition, they exhibited good ion selectivity, strong ion anti-interference ability, wide linear range (0-10 mu M), high sensitivity, and low limits of detection (29.2 and 24.6 nM). More impressively, Py-Ph and Py-Nap were elucidated with low cytotoxicity and good pH response range, and they were successfully applied to bioimaging of both exogenous and endogenous Zn2+ in living cells or tissues, suggesting their favorable application values for Zn2+ detection in reproductive health field and biomedical.