title: A two-photon ratiometric fluorescence probe for cupric ions in live cells and tissues.
abstract: Development of sensitive and selective probes for cupric ions (Cu(2+)) at cell and tissue level is a challenging work for progress in understanding the biological effects of Cu(2+). Here, we report a ratiometric two-photon probe for Cu(2+) based on the organic-inorganic hybrids of graphene quantum dots (GQDs) and Nile Blue dye. Meanwhile, Cu-free derivative of copper-zinc superoxide dismutase (SOD) - E2Zn2SOD is designed as the unique receptor for Cu(2+) and conjugated on the surface of GQDs. This probe shows a blue-to-yellow color change in repose to Cu(2+), good selectivity, low cytotoxicity, long-term photostability, and insensitivity to pH over the biologically relevant pH range. The developed probe allows the direct visualization of Cu(2+) levels in live cells as well as in deep-tissues at 90-180 μm depth through the use of two-photon microscopy. Furthermore, the effect of ascorbic acid is also evaluated on intracellular Cu(2+) binding to E2Zn2SOD by this probe.
authors.affiliation: Department of Chemistry, Tongji University, Siping Road 1239, Shanghai 200092, China.
authors.forename: Anwei
authors.initials: A
authors.lastname: Zhu
authors.forename: Changqin
authors.initials: C
authors.lastname: Ding
authors.forename: Yang
authors.initials: Y
authors.lastname: Tian
mesh_terms: D002412:Cations / Q000737:chemistry*; D045744:Cell Line, Tumor; D003300:Copper / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006108:Graphite / Q000737:chemistry; D006801:Humans; D061848:Optical Imaging / Q000379:methods; D017785:Photons; D045663:Quantum Dots / Q000737:chemistry
chemical_list: D002412:Cations; D005456:Fluorescent Dyes; D006108:Graphite; D003300:Copper