Fluorescence turn-on detection of Sn2+ in live eukaryotic and prokaryotic cells

Abstract

Sn²⁺ is usually added to toothpaste to prevent dental plaque and oral disease. However, studies of its physiological role and bacteriostatic mechanism are restricted by the lack of versatile Sn²⁺ detection methods applicable to live cells, including Streptococcus mutans. Here we report two Sn²⁺ fluorescent probes containing a rhodamine B derivative as a fluorophore, linked via the amide moiety to N,N-bis(2-hydroxyethyl)ethylenediamine (R1) and tert-butyl carbazate group (R2), respectively. These probes can selectively chelate Sn²⁺ and show marked fluorescence enhancement due to the ring open reaction of rhodamine induced by Sn²⁺ chelation. The probes have high sensitivity and selectivity for Sn²⁺ in the presence of various relevant metal ions. Particularly, both R1 and R2 can target lysosomes, and R2 can probe Sn concentrations in lysosomes with rather acidic microenvironment. Furthermore, these two probes have low toxicity and can be used as imaging probes for monitoring Sn²⁺ not only in live KB cells (eukaryotic) but also in Streptococcus mutans cells (prokaryotic), which is a useful tool to study the physiological function of Sn²⁺ in biological systems.