Photodynamic therapy (
PDT) is a great potential anti-
tumor therapy owing to its non-invasiveness and high spatiotemporal selectivity. However, systemically administered
photosensitizers diffuse in the skin and the eyes for a long duration, which cause
phototoxicity to bright light and sunlight. Therefore, following
PDT, patients must avoid exposure of to light and sunlight to avoid this
phototoxicity. In this study, we have developed a locally administered
PDT using nano-adhesive
porphyrin with
polycations consisting of quaternary
ammonium salt groups (aHP) as a
photosensitizer. The aHP, approximately 3.0 nm in diameter, adhered the negatively charged cell membrane via electrostatic interaction. The aHP localized to the endosome via cell adhesion and induced apoptosis upon 635 nm light irradiation. On being administered subcutaneously on the
tumor, 30% of the injected aHP remained in the administered sites. However, low-molecular-weight
hematoporphyrin dihydrochloride (HP) disappeared due to rapid diffusion.
PDT with locally administered aHP showed a higher anti-
tumor effect after light irradiation at 635 nm for three days compared to low-molecular-weight HP. Intraperitoneal administration of HP caused severe
phototoxicity upon irradiation with ultraviolet A
at 10 J cm-2, whereas aHP did not cause
phototoxicity because its diffusion into the skin could be suppressed, probably due to the high-molecular weight of aHP. Therefore, locally administered
PDT with aHP is a potential
PDT having high therapeutic efficacy without
phototoxicity.