Intramolecular fluorescence resonance energy transfer and living cell imaging of novel pyridyltriphenylamine dye

• Two novel fluorescent compounds were synthesized based on pyridyltriphenylamine building block.
• Probe PTRh can selectively recognize Hg2+ based on fluorescence resonance energy transfer (FRET).
• Dye PTO was sucessfully encapsulated in silica nanoparticles and emitted bright blue fluorescence.
• Both probe PTRh and PTO-doped silica nanoparticles could be successfully used as biosensors when uptaken by living cells.

A novel pyridyltriphenylamine-rhodamine dye PTRh and a pyridyltriphenylamine derivative PTO were synthesized and characterized by 1H NMR and HRMS-MALDI-TOF. PTRh performed typical fluorescence resonance energy transfer (FRET) signal from pyridyltriphenylamine to rhodamine along with notable color change from green to rose when interacting with Hg2+ in EtOH/H2O. And PTRh as a ratiometric probe for Hg2+ based on FRET could achieve a very low detection limit of 32 nM and energy transfer efficiency of 83.7% in aqueous organic system. On the other hand, spectra properties of PTO in its aggregates, THF/H2O mixed solution and silica nanoparticles (Si-NPs) dispersed in water were investigated. And the results indicated PTO exhibited bright green fluorescence in solid state, and PTO was successfully encapsulated in silica matrix (30–40 nm), emitting bright blue fluorescence with 11.7% quantum yield. Additionally, living cell imaging experiments demonstrated that PTRh could effectively response to intracellular Hg2+ and PTO-doped Si-NPs were well uptaken by MCF-7 breast cancer cells. It could be concluded that the chromophores are promising materials used as biosensors.

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