Rational design and DFT studies of fluorescence probe with dual receptor units for simultaneous multiple targets sensing in aqueous solution along with living cells image and logic gate

A multi-responsive fluorescence probe NPH was rational configured on the receptor1-fluorophore-receptor2 model to discriminatively detect Al3+, Mg2+ and Zn2+. The probe NPH contained benzooxazole moiety (receptor1) and 2-aldimine-phenol unit (receptor2), which showed fluorescence turn on response for Al3+, Mg2+ and Zn2+ in DMF/H2O (9/1, V/V, pH = 7.4) medium and sensing mechanism was studied by H-1 NMR, FT-IR and further confirmed by DFT calculation. The presence Mg2+ inhibited ESIPT and C = N isomerization processes, but the presence Al3+ caused a moderate deprotonation of the naphtholic OH. Finally, the presence of Zn2+ completely deprotonated the naphtholic OH and phenolic OH. The presence of Al3+, Mg2+ and Zn2+ resulted in the different degree deprotonation processes, which resulted the fluorescence responses at different emission wavelength. Interestingly, after addition of EDTA to the NPH/Al3+ complex, caused a new and strong emission peak at 560 nm along with a remarkable color change from yellow-green to yellow-orange, and the value of fluorescence intensity at 560 nm was linearly proportional to the concentration of EDTA. The NPH/Al3+ complex could serve as a fluorescence colorimetric probe for the detection EDTA. In addition, probe NPH was applied in real water samples and construction of molecular logic gate. Importantly, fluorescence image experiments of Al-3+,Al- Mg2+, Zn2+ and EDTA in living HeLa cells and HepG cells confirmed its value in biological system.

Automated summary

The multi-responsive fluorescence probe NPH was designed to detect Al3+, Mg2+ and Zn2+ through a receptor1-fluorophore-receptor2 model. The probe showed different fluorescence responses for each metal ion and could be used as a colorimetric probe for EDTA detection. Additionally, NPH was successfully applied in real water samples and the construction of a molecular logic gate, demonstrating its potential value in biological systems.