title: Fluorescence lifetime imaging and FRET-induced intracellular redistribution of Tat-conjugated quantum dot nanoparticles through interaction with a phthalocyanine photosensitiser.
abstract: The interaction of Tat-conjugated PEGylated CdSe/ZnS quantum dots (QD) with the amphiphilic disulfonated aluminium phthalocyanine photosensitiser is investigated in aqueous solution and in a human breast cancer cell line. In aqueous solution, the QDs and phthalocyanine form stable nanocomposites. Using steady-state and time-resolved fluorescence measurements combined with singlet oxygen detection, efficient Förster resonance energy transfer (FRET) is observed with the QDs acting as donors, and the phthalocyanine photosensitiser, which mediates production of singlet oxygen, as acceptors. In cells, the Tat-conjugated QDs localise in lysosomes and the QD fluorescence lifetimes are close to values observed in aqueous solution. Strong FRET-induced quenching of the QD lifetime is observed in cells incubated with the nanocomposites using fluorescence lifetime imaging microscopy (FLIM). Using excitation of the QDs at wavelengths where phthalocyanine absorption is negligible, FRET-induced release of QDs from endo/lysosomes is confirmed using confocal imaging and FLIM, which is attributed to photooxidative damage to the endo/lysosomal membranes mediated by the phthalocyanine acceptor.
authors.affiliation: National Medical Laser Centre, Division of Surgery & Interventional Science and UCL Institute for Biomedical Engineering, University College London, London, UK.
authors.forename: Elnaz
authors.initials: E
authors.lastname: Yaghini
authors.forename: Francesca
authors.initials: F
authors.lastname: Giuntini
authors.forename: Ian M
authors.initials: IM
authors.lastname: Eggleston
authors.forename: Klaus
authors.initials: K
authors.lastname: Suhling
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Seifalian
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: MacRobert
mesh_terms: D031541:Fluorescence Resonance Energy Transfer / Q000379:methods*; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D042541:Intracellular Space / Q000378:metabolism*; D054833:Isoindoles; D061986:MCF-7 Cells; D008856:Microscopy, Fluorescence; D053758:Nanoparticles / Q000737:chemistry*; D061848:Optical Imaging / Q000379:methods*; D017319:Photosensitizing Agents / Q000494:pharmacology*; D045663:Quantum Dots / Q000378:metabolism*; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*
chemical_list: D007211:Indoles; D054833:Isoindoles; D017319:Photosensitizing Agents; D054322:tat Gene Products, Human Immunodeficiency Virus; C013647:phthalocyanine
keywords: fluorescence lifetime imaging microscopy (FLIM); förster resonance energy transfer (FRET); photochemical internalization (PCI); photodynamic therapy; quantum dots