Fluorescent organic nanoparticles (FONs) for selective recognition of Al3+: application to bio-imaging for bacterial sample

Abstract

The development of a novel chemo-sensor for the detection of Al³⁺ with high sensitivity in aqueous solution is widely considered an important research goal because of the importance of such probes in medicine, living systems and the environment. In this work, we describe a new fluorescent probe, a Schiff's base N,N′-propylenebis(salicylimine) (salpn) as fluorescent organic nanoparticles for Al³⁺. The study shows that salpn detects Al³⁺ with the detection limit as low as 1.24 × 10⁻³ mM, indicating that the chemo-sensor has high sensitivity in aqueous medium, and the fluorescence intensity increases with the increasing Al³⁺ concentration in the presence of the salpn-ONPs which act as chemo-sensors. The interference of common coexistent metal ions such as Mn²⁺, Mg²⁺, Co²⁺, Fe³⁺, Ni²⁺, Zn²⁺, Sr²⁺, Ag⁺, Sm³⁺, Al³⁺, Cd²⁺, Ba²⁺, Na⁺ and K⁺ was tested, showing that salpn-ONPs efficiently detect Al³⁺ ions with small interference from Cu²⁺ and Cr³⁺. Finally, the efficiency of salpn to as a fluorescent probe for Al ion in living systems was evaluated in Gram-negative and Gram positive bacteria, and con-focal laser scanning microscopy confirms its utility that this chemo-sensor efficiently detects Al³⁺ ion in Staphylococcus aureus enclosed by a single membrane.