Polycation liposome enhances the endocytic uptake of photosensitizer into cells in the presence of serum.

To construct a novel drug delivery carrier that possesses high therapeutic efficacy with low dosage, we designed polyethylenimine-modified liposome (polycation liposome, PCL) and examined the entrapment of photosensitizer, benzoporphyrin derivative monoacid ring A (BPD-MA), for antiangiogenic photodynamic therapy (PDT). Photosensitizer entrapped in PCLs showed enhanced phototoxicity for a human vascular endothelial cell line, ECV304, in comparison with that for nonmodified control liposome. Interestingly, phototoxicity of control liposomal BPD-MA was suppressed in the presence of serum, but PCL maintained the phototoxicity in the presence of serum following PCL-mediated PDT treatment due to the stability of PCL and the reduced detachment of encapsulated photosensitizer from liposome to serum. In fact, PCL enhanced the uptake level of BPD-MA to ECV304 cells despite the presence or absence of serum. Since polycation modification enhances bioavailability of the liposomal photosensitizer and this property is maintained in the presence of serum, PCL would be useful for antiangiogenic PDT.