Development of novel formulations for photodynamic therapy on the basis of amphiphilic polymers and porphyrin photosensitizers. Porphyrin-polymer complexes in model photosensitized processes

We have studied the effect of amphiphilic polymers with different structure (polyvinylpyrrolidone, polyethyleneoxide and a triblock copolymer of ethylene- and propyleneoxide-(Pluronic F127)) on the photoactivity of a hematoporphyrin derivative (dimegin). It has been shown that such polymers can cause a considerable increase in the porphyrin photosensitizer (PPS) activity both in the process of singlet oxygen photogeneration and in the reaction of a substrate photooxidation in D2O and water. Among the studied polymers, polyvinylpyrrolidone appeared to have a most significant influence onto the photoactivity of dimegin. We attribute the observed effect of the amphiphilic polymers on the photoactivity of dimegin to the presence of polymer-porphyrin interactions resulting in the porphyrin disaggregation in aqueous phase. Using 1H NMR spectroscopy, we have found that dimegin binds to the polymers via the PPS interaction mainly with the hydrophobic fragments of polymeric macromolecules. However, in the case of polyvinylpyrrolidone we observed also PPS interactions with the hydrophilic fragments of macromolecules.