ACCys: A fluorescent probe for highly sensitive tandem detection of aluminum (III), copper (II), and cysteine

Abstract

Aluminum and copper are associated with health risks and environmental concerns and have been mandated by WHO, among other agencies, as having a low limit of toxicity. Therefore, a simple and cost-effective method to detect and track Al³⁺ and Cu²⁺ in biological and environmental samples using fluorescence probe is paramount in biomedical research. In this study, we developed a novel Schiff base fluorescent probe ACCys (C₁₇H₁₆O₄N₂) bearing phenol and hydrazone groups for the selective and tandem detection of Al³⁺, Cu²⁺, and cysteine (Cys). ACCys exhibited a fluorescence “turn-on” response in the presence of [Al³⁺], a “turn-off” response in the presence of [Cu²⁺], and a fluorescence recovery with [Cys] addition. The binding stoichiometry, binding constants, and electronic properties were confirmed using spectroscopic and density functional theory (DFT) studies. ACCys demonstrated excellent sensitivity for Al³⁺ (Ka = 3.78 × 10³ M⁻¹), Cu²⁺ (Ka = 8.12 × 10⁴ M⁻¹), and Cys with the limit of detection of 72.7 nM, 140.6 nM, and 168 nM, respectively. Furthermore, ACCys successfully detected intracellular Al³⁺ ions in live-cell imaging and accurately quantified Al³⁺ levels in analytical water samples from different environmental sources. The selectivity, reversibility, and biocompatibility of ACCys make it a promising tool for real-time monitoring of Al³⁺ and Cu²⁺ in biological and environmental samples. The ability of ACCys to detect Cys with a fluorescence “turn-on” effect makes it unique and highly applicable for detecting multiple analytes with high selectivity and sensitivity.