Single Probe for Imaging and Biosensing of pH, Cu<sup>2+</sup> Ions, and pH/Cu<sup>2+</sup> in Live Cells with Ratiometric
Fluorescence Signals
- Publication date
- 2015
- Publisher
Abstract
It
is very essential to disentangle the complicated inter-relationship
between pH and Cu in the signal transduction and homeostasis. To this
end, reporters that can display distinct signals to pH and Cu are
highly valuable. Unfortunately, there is still no report on the development
of biosensors that can simultaneously respond to pH and Cu<sup>2+</sup>, to the best of our knowledge. In this work, we developed a single
fluorescent probe, AuNC@FITC@DEAC (AuNC, gold cluster; FITC, fluorescein
isothiocyanate; DEAC, 7-diethylaminocoumarin-3-carboxylic acid), for
biosensing of pH, Cu<sup>2+</sup>, and pH/Cu<sup>2+</sup> with different
ratiometric fluorescent signals. First, 2,2′,2″-(2,2′,2″-nitrilotris(ethane-2,1-diyl)tris((pyridin-2-yl-methyl)azanediyl))triethanethiol
(TPAASH) was designed for specific recognition of Cu<sup>2+</sup>,
as well as for organic ligand to synthesize fluorescent AuNCs. Then,
pH-sensitive molecule, FITC emitting at 518 nm, and inner reference
molecule, DEAC with emission peak at 472 nm, were simultaneously conjugated
on the surface of AuNCs emitting at 722 nm, thus, constructing a single
fluorescent probe, AuNC@FITC@DEAC, to sensing pH, Cu<sup>2+</sup>,
and pH/Cu<sup>2+</sup> excited by 405 nm light. The developed probe
exhibited high selectivity and accuracy for independent determination
of pH and Cu<sup>2+</sup> against reactive oxygen species (ROS), other
metal ions, amino acids, and even copper-containing proteins. The
AuNC-based inorganic–organic probe with good cell-permeability
and high biocompatibility was eventually applied in monitoring both
pH and Cu<sup>2+</sup> and in understanding the interplaying roles
of Cu<sup>2+</sup> and pH in live cells by ratiometric multicolor
fluorescent imaging