A Europium(iii)-organic Fluorophone Compound As A Dual-responses Fluorescent PH Sensor

Intracellular pH plays many critical roles in cell,enzyme, and tissue activities, including proliferation and apoptosis, multidrug resistance (MDR),ion transport, endocytosis,and muscle contraction.Monitoring pH changes inside living cells is also important for studying cellular internalization pathways, such as phagocytosis, endocytosis, and receptor ligand internalization. Determining the fluorescence pH probe molecules for imaging purpose in living cells thus is currently intriguing the attention of chemists, and several different approaches to biological luminescence pH probes have been devised and developed in the past.A new europium(III) compound Eu-QZ1 was designed and synthesized as a pH-sensitive fluorescent probe (where QZ1 = (E)-2-(3-hydroxy-6-oxo-4-((quinolin-8- ylimino)methyl)-6H-xanthen-9-yl)benzoic acid. Eu-QZ1 comprised a green light emitting fluorescencein fluorophore and a EuIII moiety as the origin of red light. These pH-sensitive emitter components have pKa values at about 7.0-7.4. Luminescence titrations demonstrated that Eu-QZ1 exhibited high sensitivity in monitoring pH changes in neutral aqueous media with negligible background fluorescence and was able to detect pH value in cultured cells.Based on these studies,Another new Europium(III) complexes Eu-DR1 was designed and synthesized as new fluorescent pH probes. Eu-DR1 comprised a green light emitting Rhodamine 6G fluorophore, a Eu(III) moiety as the origin of red light and a blue light emitting N,N-dimethylphenylamine fluorophore. These pH-sensitive emitter components having suitable pKa values and isolated protonated steps within one molecule, thus make Eu-DR1 can be used to detect pH values at both near neutral pH condition and acidic pH range. The regulation of emission colour from red to green and white of Eu-DR1 with the change of pH and excitation wavelength demonstrated a new naked-eye detection approach to imaging pH value in living cells.