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Diblock Copolymer Micelles Deliver Hydrophobic Protoporphyrin IX for Photodynamic Therapy
Author(s) -
Li Buhong,
Moriyama Eduardo H.,
Li Fugang,
Jarvi Mark T.,
Allen Christine,
Wilson Brian C.
Publication year - 2007
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2007.00194.x
Subject(s) - protoporphyrin ix , micelle , photodynamic therapy , photosensitizer , chemistry , phototoxicity , ethylene glycol , singlet oxygen , photochemistry , copolymer , protoporphyrin , drug delivery , fluorescence , biophysics , porphyrin , organic chemistry , polymer , aqueous solution , in vitro , biochemistry , physics , oxygen , biology , quantum mechanics
Polymeric micelles are emerging as an effective drug delivery system for hydrophobic photosensitizers in photodynamic therapy (PDT). The objective of this study was to investigate the formulation of hydrophobic protoporphyrin IX (PpIX) with MePEG 5000 ‐b‐PCL 4100 [methoxy poly (ethylene glycol)‐b‐poly (caprolactone)] diblock copolymers and to compare their PDT response to that of free PpIX. The photophysical and photochemical properties of the polymeric PpIX micelles were studied by measuring absorbance and fluorescence spectra, PpIX‐loading efficiency and stability, the micelle particle size and morphology, as well as singlet oxygen luminescence and lifetime. The spherical micelles have a high PpIX‐loading efficiency of 82.4% and a narrow size distribution with a mean diameter of 52.2 ± 6.4 nm. The cellular uptake of PpIX in RIF‐1 cells using PpIX micelles was approximately two‐fold higher than that for free PpIX. Free PpIX and PpIX formulated in micelles exhibited similar subcellular localization in or around the cellular plasma membrane, as demonstrated using fluorescence microscopy. In vitro PDT results showed that the PpIX micelles have markedly increased photocytotoxicity over that with free PpIX, by nearly an order of magnitude at the highest light dose used. The micelles alone had no evident phototoxicity or dark toxicity. These findings suggest that MePEG 5000 ‐b‐PCL 4100 diblock copolymer micelles have great potential as a drug delivery system for hydrophobic photodynamic sensitizers.