Highly selective fluorescent peptide-based chemosensors for aluminium ions in aqueous solution.

Two novel fluorescent peptide-based chemosensors, including A (2-amino-benzoyl-Ser-Glu-Glu-NH) and B (2-amino-benzoyl-Ala-Glu-Pro-Glu-Ala-Glu-Pro-NH) were synthesized and characterized by nuclear magnetic resonance (NMR) spectra. These fluorescent probes exhibited excellent selective and sensitive responses to Al ions over other metal ions in aqueous buffered solutions. The limits of detection for both chemosensors towards the Al ions were in the order of ∼10 M (A: 155 nM and B: 195 nM), which clearly indicates that these probes have significant potential for biological applications. They also displayed high binding affinity (1.3029 × 10 M and 1.7586 × 10 M relevant to A and B respectively). These two chemosensors are great analytical probes that produce turn-on responses upon binding to Al ions through an intramolecular charge transfer (ICT) mechanism. In addition, the application of both chemosensors was examined over a wide range of pH. The fluorescent peptide-based probes and Al form a 1:1 coordination complex according to the ESI-MS and Job's plot analysis. Notably, upon addition of Al to these chemosensors, a fluorescence enhancement of approximately 8-fold was observed and the binding mode was determined using NMR titration and fluorescence emission data.