Preparation And Application Of Novel Lanthanide-Based Time-Gated Luminescence Nanoprobes

Lanthanide-based luminescent probes possess several distinct advantages, including long luminescence lifetimes, large Stokes shifts and sharp emission profiles, which enable them to be easily used for highly sensitive luminescence detection of analytes in complicated biological and environmental samples by time-gated (or time-resolved) mode. Recently, the rapid development of time-gated luminescence imaging technique further provides opportunities to the development and application of luminescent lanthanide bioprobes. In this doctoral dissertation, the following several lanthanide-based nanoprobes have been prepared, and their applicability for the time-gated luminescence bioassays was investigated.A new type of silica-encapsulated luminescent europium nanoparticles, with a wide excitation range from UV to visible light in aqueous media, was prepared by the copolymerization of the IPTES-BHHD-Eu3+-BPT conjugate, tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane in a water-in-oil reverse microemulsion. The nanoparticles are spherical and uniform in size (42 ± 3nm ), with a wide excitation range from UV to?475 nm and a long luminescence lifetime of 346 ?s. The nanoparticle-labeled streptavidin was prepared, and then successfully used for the time-gated luminescence imaging detection of two environmental pathogens, cryptosporidium muris and cryptosporidium parvium, in complicated water samples.A new visible-light-excited europium(III) complex, BHHBB-Eu3+-BPT, was synthesized. By encapsulating this complex into apoferritin (Aft) with a simple dissociation-reassembly method, the luminescent protein, Eu@AFt, with a maximum excitation peak at 420 nm, a long luminescence lifetime of 365 ?s and good biocompatibility, was fabricated, which could be directly used for the visible-light-excited time-gated luminescence cell imaging. By conjugating a mitochondria-targeting molecule, SPTPP, onto the surface of Eu@AFt, a mitochondria-specifically-tracking luminescent probe, Eu@AFt-SPTPP, was further prepared, and successfully used for the visible-light-excited confocal luminescence microscopy imaging to visualize the mitochondria of living cells.Using a Tb(III) complex PTTA-Tb3+ as energy donor and a rhodamine derivative as energy acceptor, a ratiometric luminescent nanoprobe for the detection of NO, PTTA-Tb3+@AFt-Rh-NO, was prepared based on the luminescence resonance energy transfer (LRET) mechanism. This LRET-based probe exhibits several useful advantages, such as long-lived luminescence, large Stokes shift, high sensitivity and selectivity, ratiometric response ability, and good bioaffinity and biocompatibility. The applicability of the new probe for the time-gated luminescence imaging of NO in living HepG2 cells and Daphnia magna bodies was demonstrated.By combining PTTA-Eu3+ and folic acid (FA) with superparamagnetic Co-Fe-O nanoparticles, a new kind of multifunctional composite nanoparticles, PTTA-Eu3+-CoFeO-FA, was prepared. The nanoparticles possessed luminescence, magnetic, and cancer cell-targeting properties. The application results for the time-gated luminescence imaging of cancer cells and for the magnetic resonance imaging (MRI) of Kunming mice suggested that the new nanoparticles could be a useful tool for the detection of cancers with luminescence-MRI dual modes.