EPR Characterisation of Phthalocyanine Radical Anions in Near‐Infrared Photocleavage of the Hydrophilic Axial Ligand of a Photoimmunotherapeutic Reagent, IR700. Issue 1 (15th November 2021)

• Record Type: Journal Article
• Authors: Inanami, Osamu; Hiraoka, Wakako; Goto, Yuto; Takakura, Hideo; Ogawa, Mikako
• Is Part Of: ChemPhotoChem. Volume 6:Issue 1(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-11-15
• Subjects: electron paramagnetic resonance -- phthalocyanine radical anions -- photoimmunotherapy -- singlet oxygen -- superoxide anion radicals; Photochemistry -- Periodicals; Periodicals; Electronic journals; 541.35
• DOI: 10.1002/cptc.202100172
• Languages: English
• ISSNs: 2367-0932

Abstract

Abstract: Photoimmunotherapy (PIT) is a novel cancer therapy that utilises tumour‐specific monoclonal antibodies coupled with a silicon phthalocyanine derivative with biaxial ligands (IR700). Near‐infrared (NIR)‐induced cleavage of these axial ligands induces the aggregation of IR700 on the cell membrane, resulting in cell death. Using electron paramagnetic resonance (EPR) spectroscopy and computer spectral simulation, NIR irradiation of the IR700 aqueous solution under hypoxia revealed induced IR700 anion radicals in the presence of an electron donor. Two types of IR700 anion radicals with different anisotropies were identified as the precursors of the two‐step NIR‐induced cleavage reaction of the axial ligand of IR700. Under aerobic conditions, NIR irradiation of IR700 aqueous solution with and without the electron donor produced 1 O2 and O2 .−, respectively. These results suggest that NIR‐induced IR700 anion radicals are important for inducing the aggregation of IR700 and O2 .− . Abstract : Photoimmunotherapy using a silicon phthalocyanine compound (IR700) with biaxial hydrophilic ligands is a novel potential cancer therapy. NIR‐induced cleavage of these biaxial hydrophilic ligands is a key reaction that produces cytotoxic aggregation during therapy. Herein, using EPR spectroscopy, two IR700 anion radicals with different anisotropies were identified as precursors for the two‐step NIR‐induced cleavage reaction of the axial ligand of IR700.