The use of polymeric carriers to deliver hydrophobic
photosensitizers has been widely discussed as a way to improve both fluorescence diagnostic and
photodynamic therapy (
PDT) of
cancers; however, the photophysical and pharmacokinetic parameters, as well as the
PDT activity, of such modifications have, until now, only been poorly investigated. The purpose of the present study was to explore the efficacy of
PDT with the formulation of the
photosensitizer chlorin e6 (Ce6) in combination with
polyvinyl alcohol (PVA) in comparison with Ce6 alone and with the clinical drug,
Photodithazine in a mouse
tumor model. We also investigated the photoactivity of the Ce6-PVA in a model reaction of
tryptophan oxidation, analyzed the polymer-Ce6 interaction using fluorescence spectroscopy and atomic-force microscopy, and tested the
phototoxicity in vitro. Using fluorescence imaging in vivo we found that injection to mice of Ce6 in a formulation with PVA resulted in a higher
tumor-to-normal ratio and greater photobleaching when compared with either the use of Ce6 alone, or with the effects of
Photodithazine.
Tumor growth study and histological examination of CT26
tumors revealed fast, reproducible
tumor regression and more advanced
necrosis after
PDT with Ce6-PVA. The higher photoactivity of the Ce6-PVA complex was confirmed in a model reaction of
tryptophan oxidation and in cultured cells. Therefore, encapsulation of Ce6 in PVA represents a promising strategy for further increasing the selectivity and efficacy of
PDT.