title: Two-photon fluorescent probe for cadmium imaging in cells.
abstract: A novel two-photon excited fluorescent probe for cadmium (named as TPCd) was designed and synthesized utilizing a prodan (6-acetyl-2-methoxynaphthalene) derivative as the two-photon fluorophore and an o-phenylenediamine derivative as the Cd(2+) chelator, which possessed favorable photophysical properties and good water-solubility. The probe was designed with a photoinduced electron transfer (PET) mechanism and thus was weakly fluorescent itself. After binding with Cd(2+) which blocked the PET process, the fluorescence intensity of the probe was enhanced by up to 15-fold under one-photon excitation (OPE) and 27-fold under two-photon excitation (TPE), respectively. The two-photon action cross-section (Φδ) of the TPCd-Cd complex at 740 nm reached 109 GM compared to 3.6 GM for free TPCd, indicating the promising prospect of the probe in two-photon application. TPCd chelated Cd(2+) with 1 : 1 stoichiometry, and the apparent dissociation constant (K(d)) was 6.1 × 10(-5) M for the one-photon mode and 7.2 × 10(-5) M for the two-photon mode. The probe responded to Cd(2+) over a wide linear range from 0.1 to 30 μM with a detection limit of 0.04 μM. High selectivity of the probe towards Cd(2+) was acquired in Tris-HCl/sodium phosphate buffer. The probe was pH-independent in the biologically relevant pH range and non-toxic to living cells at reasonable concentration levels, warranting its in vivo applications. Through two-photon microscopy imaging, the probe was successfully applied to detect Cd(2+) uptake in living HepG2 cells.
authors.affiliation: Key Laboratory of Analytical Chemistry for Biology and Medicine (Ministry of Education), College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, P. R. China.
authors.forename: Yongyou
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiaohu
authors.initials: X
authors.lastname: Dong
authors.forename: Jian
authors.initials: J
authors.lastname: Sun
authors.forename: Cheng
authors.initials: C
authors.lastname: Zhong
authors.forename: Boheng
authors.initials: B
authors.lastname: Li
authors.forename: Ximeng
authors.initials: X
authors.lastname: You
authors.forename: Bifeng
authors.initials: B
authors.lastname: Liu
authors.forename: Zhihong
authors.initials: Z
authors.lastname: Liu
mesh_terms: D002104:Cadmium / Q000032:analysis*; D045744:Cell Line, Tumor; D005456:Fluorescent Dyes / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D057230:Limit of Detection; D009682:Magnetic Resonance Spectroscopy; D008856:Microscopy, Fluorescence / Q000379:methods; D017785:Photons; D012995:Solubility; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet
chemical_list: D005456:Fluorescent Dyes; D002104:Cadmium