Development of a water-soluble fluorescent Al³⁺ probe based on phenylsulfonyl-2-pyrone in biological systems

Al exists naturally in the environment and is an important component in acidic soils, which harm almost all plants. Furthermore, Al is widely used in food additives, cosmetics, and medicines, resulting in living organisms ingesting traces of Al orally or dermally every day. Accordingly, Al accumulates in the body, which can cause negative bioeffects and diseases, and this concern is gaining increasing attention. Therefore, to detect and track Al in the environment and in living organisms, the development of novel Al-selective probes that are water-soluble and exhibit fluorescence at long wavelengths is necessary.

In this study, an Al³⁺-selective fluorescent probe PSP based on a novel pyrone molecule was synthesized and characterized to detect and track Al in biological systems. PSP exhibited fluorescence enhancement at 580 nm in the presence of Al³⁺ in aqueous media. Binding analysis using Job's plot and structural analysis using ¹H NMR showed that PSP formed a 1:1 complex with Al³⁺ at the two carbonyl groups of the dimethyl malonate of the pyrone ring. Upon testing in biological systems, PSP showed good cell membrane permeability, detected intracellular Al³⁺ in human breast cancer cells (MDA-MB-231), and successfully imaged accumulated Al³⁺ in Microcystis aeruginosa and the larvae of Rheocricotopus species.

The novel Al³⁺-selective fluorescent probe PSP is highly effective and is expected to aid in elucidating the role of Al³⁺ in the environment and living organisms.