Photodynamic therapy (PDT) for cancer treatment involves the pathology�s uptake of photosensitizers, which produce cytotoxic\nreactive oxygen species by photoirradiation. The use of nanoparticles as carriers of photosensitizers is one promising approach to\nthis endeavor, owing to their small size, unique physicochemical properties, and easy/diverse functionalization. In the current work,\nwe report on the in vivo assessment of PDT efficacy of these nanoconstructs in a murine model of human breast cancer, following\na single (one-shot) nanoparticle dose and photoirradiation. Palladium-porphyrin (PdTPP) was administered intratumorally via\ninjection of aqueous suspensions of either free PdTPP or MSN-conjugated PdTPP (MSN-PdTPP) at a dose of 50 ????g. Mice were\nthen exposed to a single photoirradiation session with total energy of 80 J. One month after one-shot PDT treatment, significantly\ngreater reductions in tumor growth were observed in MSN-Pd treated animals than in PdTPP cohorts. Electron microscopy of\ntumor specimens harvested at various timepoints revealed excellent MSN-PdTPP uptake by cancer cells while immunohistologic\nanalysis demonstrated marked increases in apoptotic response of MSN-PdTPP treated animals relative to PdTPP controls. Taken\ntogether, these findings suggest that considerable improvements in PDT efficacy can readily be achieved via the use of nanoparticlebased\nphotosensitizers.
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