Polymer nanoparticle-based ratiometric fluorescent probe for imaging Hg2+ ions in living cells

Mercury pollutant brings huge threat to human health and the environment because of its bioaccumulation and permanent damage. Thus, highly selective and ratiometric detection and imaging of Hg2+ in organisms is quite important. Herein, we report on a polymer nanoparticle-based ratiometric fluorescent probe (NP3) for highly selective recognition of Hg2+ in totally aqueous solution and imaging in living cells. This probe comprises the reference fluorescent dye (4-ethoxy-9-allyl-1,8-naphthalimide: EANI), which resides in the core of nanoparticle, and the Hg2+-recognition group (fluorescein derivative: AEMH-FITC) on the surface of nanoparticle. It displays distinct dual emissions at 432 nm and 528 nm under a single wavelength excitation. The fluorescence of the FITC moieties can be effectively quenched by Hg2+ due to photoinduced electron transfer (PET) mechanism, while that of the EANI remains constant, resulting in a ratiometric fluorescent detection of Hg2+. The as-prepared NP3 not only shows favorable water dispersibility, excellent long-term photostability, but also exhibits highly selective ratiometric detection of Hg2+ over other interfering ions (such as Cu2+, Na+, Mg2+, Zn2+, Mn2+, Ca2+, Fe3+, Cd2+, Ag+, Fe2+), and quite low detection limit (similar to 75 nM). Furthermore, intracellular fluorescence imaging experiments demonstrate that NP3 has good permeability of cell-membrane, and is able to facilitate visualization of Hg2+ changes in living cells. (C) 2016 Elsevier B.V. All rights reserved.