Synthesis And Application Of Europium/Terbium Complex-Based Luminescent Probes

Compared with traditional organic fluorescent probes, lanthanide complex-based luminescent probes have several useful advantages, such as high water-solubility, long luminescence lifetime, large Stokes shift and sharp emission profiles, which enable them to be easily used for highly sensitive luminescence detection of analytes in complicated biological samples by time-gated (or time-resolved) mode. In this doctoral dissertation, the following lanthanide complex-based luminescent probes for the specific detections of some small bioactive molecules were designed and synthesized, and their applicability for the time-gated luminescence bioassays was investigated.A cell-membrane-permeable europium complex that can be used as an efficient luminescent probe for singlet oxygen (1O2), MTDTA-Eu3+, was designed and synthesized. This probe exhibits high sensitivity and selectivity for responding to 1O2, and can be used in weakly acidic, neutral and weakly basic aqueous buffers for the time-gated luminescence detection of 1O2. Compared with the reported lanthanide complex-based luminescent probes for 1O2, the desirable cell-membrane-permeablility of the new probe enables it to permeate through the cell membrane to enter into cells easily. The probe was used for the real-time monitoring of intracellular 1O2 generation induced by two photodynamic therapy (PDT) drugs, HMME and ALA, in HeLa cells under appropriate light, which provides a valuable detection method for the PDT research of cancers.Using photoinduced electron transfer (PET) mechanism, a lanthanide complex-based ratiometric luminescence probe that can be used for the specific recognition and time-gated luminescence detection of biothiols, NSTTA-Eu3+/Tb3+, was designed and synthesized. On the basis of detailed characterization results of the probe, a ratiometric time-gated luminescence detection method for biothiols was established, and successfully used for the quantitative detection of biothiols in living cell samples.A novel lanthanide complex-based ratiometric luminescence probe for the specific recognition of H2S in neutral aqueous media, NPTTA-Eu’+/Tb3+, was designed and synthesized. On the basis of detailed characterization results of the probe, a ratiometric time-gated luminescence imaging method for H2S was established, and successfully used for the quantitative imaging of exogenous H2S molecules in living cell samples.Using luminescent Tb3+ complex as energy donor and rhodamine as energy acceptor, a unique platform based on intramolecular luminescence resonance energy transfer (LRET) for the design of ratiometric luminescent probes was constructed. On the basis of this platform, three novel ratiometric luminescent probes specific for NO, ClO- and pH, TR-NO-Tb3+, TR-ClO--Tb3+ and TR-pH-Tb3+, were synthesized, respectively. These LRET-based luminescent probes inherit the advantages of lanthanide complex-based and rhodamine-based probes, including good water-solubility, long-lived luminescence, large Stokes shifts, high sensitivity and selectivity, and excellent cell-membrane permeability. Using TR-NO-Tb3+ as a representative probe, its applicability for the ratiometric time-gated luminescence imaging of NO in living HepG2 cells and Daphnia magna was investigated. The successful construction of this platform provides a useful strategy for the design of ratiometric time-gated luminescence bioprobes.