Turn-on fluorescent probe-encapsulated micelle as colloidally stable nano-chemosensor for highly selective detection of Al3+ in aqueous solution and living cell imaging

It is well known that high amount of aluminum ion are not only detrimental to plant growth but also threat to our health. Most of fluorescent chemosensors for the detection Al3+ suffer from some restrictions, such as poor selectivity, indifferent sensitivity, inferior stability in biological fluids, and being unsuitable for the applications in aqueous environment and biological systems. To address the above limitations, we used DSPE-PEG as a carrier of fluorescent sensor (Dye) to obtain a new type of fluorescent nanochemosensor (DSPE-PEG-Dye). The hydrophobic fluorescent schiff base (Dye), synthesized by simple two-step reaction, exhibited excellent sensitivity for determination of Al3+ in the mixture of tetrahydrofuran and water (2:3, v/v). Subsequently, the Dye was successfully encapsulated in DSPE-PEG micelles to prepare the nanochemosensor (DSPE-PEG-Dye) by the solvent evaporation method, which remained the properties of Dye and displayed high selectivity and sensitivity towards Al3+ ions even in the presence of other commonly coexisting metal ions in aqueous solution. Furthermore, DSPE-PEG-Dye can act as a reversible sensor for Al3+. Sequential addition of EDTA and Al3+ into DSPE-PEG-Dye-Al3+ complex resulted in quench and recovery of fluorescence, respectively. Moreover, DSPE-PEG-Dye with low detection limit of 2.3 × 10−8 M is colloidally stable in water, PBS buffer (pH 7.4) and cell culture medium even after storage for one month. Interestingly, the nano-chemosensor exerted superior cell internalization and could be used as a nontoxic bioimaging reagent for visualizing Al3+ in living cells.