Optimizing photodynamic therapy by liposomal formulation of the photosensitizer pyropheophorbide-a methyl ester: in vitro and ex vivo comparative biophysical investigations in a colon carcinoma cell line.
Photodynamic therapy (PDT), induced by a photosensitizer (PS) encapsulated in a nanostructure, has emerged as an appropriate treatment to cure a multitude of oncological and non-oncological diseases. Pyropheophorbide-a methyl ester (PPME) is a second-generation PS tested in PDT, and is a potential candidate for future clinical applications. The present study, carried out in a human colon carcinoma cell line (HCT-116), evaluates the improvement resulting from a liposomal formulation of PPME versus free-PPME. Absorption and fluorescence spectroscopies, fluorescence lifetime measurements, subcellular imaging and co-localization analysis have been performed in order to analyze the properties of PPME for each delivery mode. The benefit of drug encapsulation in DMPC-liposomes is clear from our experiments, with a 5-fold higher intracellular drug delivery than that observed with free-PPME at similar concentrations. The reactive oxygen species (ROSs) produced after PPME-mediated photosensitization have been identified and quantified by using electron spin resonance spectroscopy. Our results demonstrate that PPME-PDT-mediated ROSs are composed of singlet oxygen and a hydroxyl radical. The small amounts of PPME inside mitochondria, as revealed by fluorescence co-localization analysis, could maybe explain the very low apoptotic cell death measured in HCT-116 cells.
Guelluy
Pierre-Henri
PH
Laboratory of Biomedical Spectroscopy, Institute of Physics, B5a, University of Liège, Sart-Tilman, B-4000, Liège, Belgium. phguelluy@ulg.ac.be
Fontaine-Aupart
Marie-Pierre
MP
Grammenos
Angeliki
A
Lécart
Sandrine
S
Piette
Jacques
J
Hoebeke
Maryse
M
D002277:Carcinoma / Q000188:drug therapy; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000188:drug therapy; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D008081:Liposomes / Q000737:chemistry; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000187:drug effects; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000008:administration & dosage* / Q000737:chemistry / Q000627:therapeutic use; D011166:Porphyrins / Q000008:administration & dosage* / Q000737:chemistry / Q000627:therapeutic use; D017382:Reactive Oxygen Species / Q000378:metabolism; D013050:Spectrometry, Fluorescence
D008081:Liposomes; D017319:Photosensitizing Agents; D011166:Porphyrins; D017382:Reactive Oxygen Species; C452939:pyropheophorbide-a methylester; D004134:Dimyristoylphosphatidylcholine