Near-infrared molecular imaging probes based on chlorin-bacteriochlorin dyads

Marcin Ptaszek, Hooi Ling Kee, Chinnasamy Muthiah, Ralph Nothdurft, Walter Akers, Samuel Achilefu, Joseph P. Culver, Dewey Holten

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

9 Scopus citations


Chlorin-bacteriochlorin dyads as a new class of near-infrared fluorophores were synthesized and spectroscopically characterized. Each dyad is comprised of a chlorin macrocycle (free base or zinc chelate) as an energy donor (and absorber) and a free base bacteriochlorin as an energy acceptor (and emitter). Excitation of the chlorin (λ= 650 nm, zinc chelate; 675 nm, free base) results in fast (5 ps) and nearly quantitative (>99%) energy transfer to the adjacent bacteriochlorin moiety, and consequently bacteriochlorin fluorescence (λ= 760 nm). Thus, each chlorinbacteriochlorin dyad behaves as a single chromophore, with a large effective Stokes shift (85 or 110 nm), a significant fluorescence quantum yield (Φf = 0.19), long excited-state lifetime (τ = 5.4 ns), narrow excitation and emission bands (<20 nm), and high chemical stability. Imaging experiments performed using phantoms show that the chlorin-bacteriochlorin dyads exhibit a range of superior properties compare with commercially available imaging dyes. While the latter are six-fold brighter (comparing ε·Φf values), the chlorin-bacteriochlorin dyads exhibit narrower excitation and emission bands and larger Stokes shift, therefore allowing more efficient and selective excitation and detection of fluorescence. The high selectivity is further demonstrated with in vivo imaging studies using mice. This selectivity together with the tunability of absorption and emission wavelengths using substituent effects under synthetic control make the chlorin-bacteriochlorin dyads ideal candidates for multicolor imaging applications. In addition, the long fluorescence lifetimes make those probes suitable for lifetime-imaging applications.

Original languageEnglish
Title of host publicationReporters, Markers, Dyes, Nanoparticles, and Molecular Probes for Biomedical Applications II
StatePublished - 2010
EventReporters, Markers, Dyes, Nanoparticles, and Molecular Probes for Biomedical Applications II - San Francisco, CA, United States
Duration: Jan 25 2010Jan 27 2010

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
ISSN (Print)1605-7422


ConferenceReporters, Markers, Dyes, Nanoparticles, and Molecular Probes for Biomedical Applications II
Country/TerritoryUnited States
CitySan Francisco, CA


  • Bacteriochlorin
  • Chlorin
  • Energy transfer
  • Fluorescence
  • In vivo imaging
  • Near-infrared fluorophores


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