title: Triplet-triplet annihilation upconversion based nanocapsules for bioimaging under excitation by red and deep-red light.
abstract: Non-toxic and biocompatible triplet-triplet annihilation upconversion based nanocapsules (size less than 225 nm) were successfully fabricated by the combination of miniemulsion and solvent evaporation techniques. A first type of nanocapsules displays an upconversion spectrum characterized by the maximum of emission at λmax = 550 nm under illumination by red light, λexc = 633 nm. The second type of nanocapsules fluoresces at λmax = 555 nm when excited with deep-red light, λexc = 708 nm. Conventional confocal laser scanning microscopy (CLSM) and flow cytometry were applied to determine uptake and toxicity of the nanocapsules for various (mesenchymal stem and HeLa) cells. Red light (λexc = 633 nm) with extremely low optical power (less than 0.3 μW) or deep-red light (λexc = 708 nm) was used in CLSM experiments to generate green upconversion fluorescence. The cell images obtained with upconversion excitation demonstrate order of magnitude better signal to background ratio than the cell images obtained with direct excitation of the same fluorescence marker.
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128, Mainz, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Wohnhaas
authors.forename: Volker
authors.initials: V
authors.lastname: Mailänder
authors.forename: Melanie
authors.initials: M
authors.lastname: Dröge
authors.forename: Mikhail A
authors.initials: MA
authors.lastname: Filatov
authors.forename: Dmitry
authors.initials: D
authors.lastname: Busko
authors.forename: Yuri
authors.initials: Y
authors.lastname: Avlasevich
authors.forename: Stanislav
authors.initials: S
authors.lastname: Baluschev
authors.forename: Tzenka
authors.initials: T
authors.lastname: Miteva
authors.forename: Katharina
authors.initials: K
authors.lastname: Landfester
authors.forename: Andrey
authors.initials: A
authors.lastname: Turshatov
mesh_terms: D058948:Cell Tracking / Q000379:methods*; D005434:Flow Cytometry; D005453:Fluorescence; D006367:HeLa Cells; D006801:Humans; D008027:Light; D018613:Microscopy, Confocal; D053769:Nanocapsules / Q000008:administration & dosage / Q000737:chemistry*; D010316:Particle Size
chemical_list: D053769:Nanocapsules
keywords: confocal laser scanning microscopy; living cell imaging; polymer nanocapsules; triplet-triplet annihilation upconversion