Solubilization of poorly soluble PDT agent, meso-tetraphenylporphin, in plain or immunotargeted PEG-PE micelles results in dramatically improved cancer cell killing in vitro

Poorly soluble photodynamic therapy (PDT) agent, meso-tetratphenylporphine (TPP), was effectively solubilized using non-targeted and tumor-targeted polymeric micelles prepared of polyethylene glycol/phosphatidyl ethanolamine conjugate (PEG-PE). Encapsulation of TPP into PEG-PE-based micelles and immunomicelles (bearing an anti-cancer monoclonal 2C5 antibody) resulted in significantly improved anticancer effects of the drug at PDT conditions against murine (LLC, B16) and human (MCF-7, BT20) cancer cells in vitro. For this purpose, the cells were incubated for 6 or 18 h with the TPP or TPP-loaded PEG-PE micelles/immunomicelles and then light-irradiated for 30 min. The phototoxic effect depended on the TPP concentration and specific targeting by immunomicelles. An increased level of apoptosis was shown in the PDT-treated cultures. The attachment of the anti-cancer 2C5 antibodies to TPP-loaded micelles provided the maximum level of cell killing at a given time. The results of this study showed that TPP-containing PEG-PE micelles may represent a useful formulation of the photosensitizer for practical PDT.