In vivo stability and photodynamic efficacy of fluorinated bacteriopurpurinimides derived from bacteriochlorophyll-a

The stable bacteriopurpurinimide (788 nm, ε: 38 600 in CH ₂Cl₂), obtained by reducing the corresponding unstable Schiff base (803 nm, ε: 50 900 in CH₂Cl₂) that was isolated by reacting bacteriopurpurin methyl ester with 3,5-bis- (trifluoromethyl)benzylamine, produced promising photosensitizing efficacy. ¹H NMR, mass spectrometry, and HPLC analyses confirmed the structures of new bacteriopurpurinimides and the metabolic product. The preliminary in vivo photosensitizing efficacy of this stable bacteriopurpurinimide was determined in C3H mice bearing radiation induced fibrosarcoma tumors as a function of variable drug doses. A drug dose of 1.0 μmol/kg and light exposure of 135 J/cm² (75 mW/cm²; 24 h postinjection) at 796 nm for 30 min produced a 60% long-term tumor cure (3/5 mice were tumor-free on day 90). Colocalization study of the stable bacteriopurpurinimide with Mito Tracker Green confirmed some mitochondrial localization. The fluorescein-exclusion assay and histological staining of CD3I confirmed vascular stasis at various time points post-PDT (post photodynamic therapy). The treatment parameters (time for maximum drug uptake and wavelength for light irradiation) were determined by in vivo reflectance spectroscopy.