Self-Assembly of Porphyrin-Paclitaxel Conjugates Into Nanomedicines: Enhanced Cytotoxicity due to Endosomal Escape.

Nanomedicines assembled directly from drug molecules possess several advantages, including precise molecular structure and high content of drugs. Herein, porphyrin-paclitaxel conjugates (Py-s-s-PTX) were synthesized by using a disulfide bond as a linker. The Py-s-s-PTX could self-assemble into nanoparticles (Py-s-s-PTX NPs) with a size of about 100 nm via disulfide-induced assembly. Py-s-s-PTX NPs are highly stable under biological conditions and could be destroyed in the presence of reducing agents as revealed by dynamic light scattering. The obtained Py-s-s-PTX NPs could be internalized by cancer cells via endocytosis and disassociated in the reducing cytoplasm, thus releasing PTX in cancer cells. Endosomal escape triggered upon irradiation could enhance the cytotoxicity of paclitaxel, and Py-s-s-PTX NPs possess cytotoxicity comparable to that of free PTX. We believe that this disulfide-assembled nanomedicine represents a new and important development for chemotherapy in cancer therapy.