Metal Complexes for Two-Photon Photodynamic Therapy: A Cyclometallated Iridium Complex Induces Two-Photon Photosensitization of Cancer Cells under Near-IR Light

Luke K. McKenzie, Igor V. Sazanovich, Elizabeth Baggaley, Mickaële Bonneau, Véronique Guerchais, J. A.Gareth Williams, Julia A. Weinstein*, Helen E. Bryant

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

139 Scopus citations

Abstract

Photodynamic therapy (PDT) uses photosensitizers (PS) which only become cytotoxic upon light-irradiation. Transition-metal complexes are highly promising PS due to long excited-state lifetimes, and high photo-stabilities. However, these complexes usually absorb higher-energy UV/Vis light, whereas the optimal tissue transparency is in the lower-energy NIR region. Two-photon excitation (TPE) can overcome this dichotomy, with simultaneous absorption of two lower-energy NIR-photons populating the same PS-active excited state as one higher-energy photon. We introduce two low-molecular weight, long-lived and photo-stable iridium complexes of the [Ir(N^C)2(N^N)]+ family with high TP-absorption, which localise to mitochondria and lysosomal structures in live cells. The compounds are efficient PS under 1-photon irradiation (405 nm) resulting in apoptotic cell death in diverse cancer cell lines at low light doses (3.6 J cm−2), low concentrations, and photo-indexes greater than 555. Remarkably 1 also displays high PS activity killing cancer cells under NIR two-photon excitation (760 nm), which along with its photo-stability indicates potential future clinical application.

Original languageEnglish (US)
Pages (from-to)234-238
Number of pages5
JournalChemistry - A European Journal
Volume23
Issue number2
DOIs
StatePublished - Jan 5 2017

Keywords

  • cancer therapy
  • iridium
  • singlet oxygen
  • transition metals
  • two-photon photodynamic therapy

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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