ABSTRACT
The stable bacteriopurpurinimide (788 nm, epsilon: 38,600 in CH2Cl2), obtained by reducing the corresponding unstable Schiff base (803 nm, epsilon: 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 micromol/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 MitoTracker Green confirmed some mitochondrial localization. The fluorescein-exclusion assay and histological staining of CD31 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.
Subject(s)
Bacteriochlorophyll A/chemistry , Fluorine , Imides/chemical synthesis , Photochemotherapy , Photosensitizing Agents/chemical synthesis , Porphyrins/chemical synthesis , Animals , Benzylamines/chemistry , Cell Line, Tumor , Cell Survival/drug effects , Chromatography, High Pressure Liquid , Drug Stability , Female , Fibrosarcoma/drug therapy , Imides/pharmacology , Mice , Neoplasms, Radiation-Induced/drug therapy , Oxidation-Reduction , Photosensitizing Agents/chemistry , Photosensitizing Agents/pharmacokinetics , Photosensitizing Agents/pharmacology , Porphyrins/pharmacokinetics , Porphyrins/pharmacology , Skin/blood supply , Skin/drug effects , Skin/radiation effectsABSTRACT
Optical imaging has attracted a great attention for studying molecular recognitions because minute fluorescent tracers can be detected in homogeneous and heterogeneous media with existing laboratory instruments. In our preliminary study, a clinically relevant photosensitizer (HPPH, a chlorophyll-a analog) was linked with a cyanine dye (with required photophysical characteristics but limited tumor selectivity), and the resulting conjugate was found to be an efficient tumor imaging (fluorescence imaging) and photosensitizing agent. Compared to HPPH, the presence of the cyanine dye moiety in the conjugate produced a significantly higher uptake in tumor than skin. At a therapeutic/imaging dose, the conjugate did not show any significant skin phototoxicity, a major drawback associated with most of the porphyrin-based photosensitizers. These results suggest that tumor-avid porphyrin-based compounds can be used as "vehicles" to deliver the desired fluorescent agent(s) to tumor. The development of tumor imaging or improved photodynamic therapy agent(s) by itself represents an important step, but a dual function agent (fluorescence imaging and photodynamic therapy) provides the potential for tumor detection and targeted photodynamic therapy, combining two modalities into a single cost-effective "see and treat" approach.
