Two-Photon Ratiometric Fluorescent Sensor Based on Specific Biomolecular Recognition for Selective and Sensitive Detection of Copper Ions in Live Cells

• Published in: Analytical chemistry (Washington) 2013-12, Vol.85 (24), p.11936-11943
• Main Authors: Fu, Yan, Ding, Changqin, Zhu, Anwei, Deng, Zifeng, Tian, Yang, Jin, Ming
• Format: Article
• Language: English
• Subjects: Amines - chemistry; Amino acids; Analytical chemistry; Animals; Atoms & subatomic particles; Biosensing Techniques - methods; Cattle; Cell Survival; Constants; Copper; Copper - metabolism; Derivatives; Emission; Fluorescence; Fluorescent Dyes - chemistry; HeLa Cells; Humans; Ions; Microscopy, Fluorescence, Multiphoton - methods; Nanostructure; Permeability; Quantum Dots; Recognition; Superoxide Dismutase - chemistry; Superoxide Dismutase - metabolism; Zinc
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac403527c

In this work, we develop a ratiometric two-photon fluorescent probe, ATD@QD-E2Zn2SOD (ATD = amino triphenylamine dendron, QD = CdSe/ZnSe quantum dot, E2Zn2SOD = Cu-free derivative of bovine liver copper–zinc superoxide dismutase), for imaging and sensing the changes of intracellular Cu2+ level with clear red-to-yellow color change based on specific biomolecular recognition of E2Zn2SOD for Cu2+ ion. The inorganic–organic nanohybrided fluorescent probe features two independent emission peaks located at 515 nm for ATD and 650 nm for QDs, respectively, under two-photon excitation at 800 nm. Upon addition of Cu2+ ions, the red fluorescence of QDs drastically quenches, while the green emission from ATD stays constant and serves as a reference signal, thus resulting in the ratiometric detection of Cu2+ with high accuracy by two-photon microscopy (TPM). The present probe shows high sensivity, broad linear range (10–7–10–3 M), low detection limit down to ∼10 nM, and excellent selectivity over other metal ions, amino acids, and other biological species. Meanwhile, a QD-based inorganic-organic probe demonstrates long-term photostability, good cell-permeability, and low cytotoxicity. As a result, the present probe can visualize Cu2+ changes in live cells by TPM. To the best of our knowledge, this is the first report for the development of a QD-based two-photon ratiometric fluorescence probe suitable for detection of Cu2+ in live cells.