title: Triplet-triplet annihilation upconversion followed by FRET for the red light activation of a photodissociative ruthenium complex in liposomes.
abstract: Upconversion is a promising way to trigger high-energy photochemistry with low-energy photons. However, combining upconversion schemes with non-radiative energy transfer is challenging because bringing several photochemically active components in close proximity results in complex multi-component systems where quenching processes may deactivate the whole assembly. In this work, PEGylated liposomes were prepared that contained three photoactive components: a porphyrin dye absorbing red light, a perylene moiety emitting in the blue, and a light-activatable ruthenium prodrug sensitive to blue light. Time-dependent spectroscopic studies demonstrate that singlet perylene excited states are non-radiatively transferred to the nearby ruthenium complex by Förster resonance energy transfer (FRET). Under red-light irradiation of the three-component membranes, triplet-triplet annihilation upconversion (TTA-UC) occurs followed by FRET, which results in a more efficient activation of the ruthenium prodrug compared to a physical mixture of two-component upconverting liposomes and liposomes containing only the ruthenium complex. This work represents a rare example where TTA-UC and Förster resonance energy transfer are combined to achieve prodrug activation in the phototherapeutic window.
authors.affiliation: Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands. bonnet@chem.leidenuniv.nl.
authors.forename: Sven H C
authors.initials: SH
authors.lastname: Askes
authors.forename: Miroslav
authors.initials: M
authors.lastname: Kloz
authors.forename: Gilles
authors.initials: G
authors.lastname: Bruylants
authors.forename: John T M
authors.initials: JT
authors.lastname: Kennis
authors.forename: Sylvestre
authors.initials: S
authors.lastname: Bonnet
mesh_terms: D004735:Energy Transfer; D031541:Fluorescence Resonance Energy Transfer; D008027:Light; D008081:Liposomes / Q000737:chemistry*; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D055668:Photochemical Processes; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D008081:Liposomes; D009942:Organometallic Compounds; D012428:Ruthenium