Corrigendum to "Protoporphyrin IX tracer fluorescence modulation for improved brain tumor cell lines visualization"

Nanoparticles that target the mitochondria of tumor cells to restore oxygen supply for photodynamic therapy: Design and preclinical validation against breast cancer

Photodynamic therapy, in which photosensitizers locally generate cytotoxic reactive oxygen species, can treat tumor tissue with minimal effects on surrounding normal tissue, but it can be ineffective because of the anoxic tumor microenvironment. Here we developed a strategy to inactivate the mitochondria of tumor cells in order to ensure adequate local oxygen concentrations for photodynamic therapy. We conjugated the photosensitizer 5-aminolevulinic acid to the lipophilic cation triphenylphosphine, which targets mitochondria. Then we packaged the conjugate into nanoparticles that were based on biocompatible bovine serum albumin and coated with folic acid in order to target the abundant folate receptors on the tumor surface. In studies in cell culture and BALB/c mice bearing MCF-7 xenografts, we found that the nanoparticles helped solubilize the cation-photosensitizer conjugate, prolong its circulation, and enhance its photodynamic antitumor effects. We confirmed the ability of the nanoparticles to target tumor cells and their mitochondria using confocal laser microscopy and in vivo assays of pharmacokinetics, pharmacodynamics, and tissue distribution. Our results not only identify a novel nanoparticle system for treating cancer, but they demonstrate the feasibility of enhancing photodynamic therapy by reducing oxygen consumption within tumors.

Boosting 5-ALA-based photodynamic therapy by a liposomal nanomedicine through intracellular iron ion regulation

5-Aminolevulinic acid (5-ALA) has been approved for clinical photodynamic therapy (PDT) due to its negligible photosensitive toxicity. However, the curative effect of 5-ALA is restricted by intracellular biotransformation inactivation of 5-ALA and potential DNA repair of tumor cells. Inspired by the crucial function of iron ions in 5-ALA transformation and DNA repair, a liposomal nanomedicine (MFLs@5-ALA/DFO) with intracellular iron ion regulation property was developed for boosting the PDT of 5-ALA, which was prepared by co-encapsulating 5-ALA and DFO (deferoxamine, a special iron chelator) into the membrane fusion liposomes (MFLs). MFLs@5-ALA/DFO showed an improved pharmaceutical behavior and rapidly fused with tumor cell membrane for 5-ALA and DFO co-delivery. MFLs@5-ALA/DFO could efficiently reduce iron ion, thus blocking the biotransformation of photosensitive protoporphyrin IX (PpIX) to heme, realizing significant accumulation of photosensitivity. Meanwhile, the activity of DNA repair enzyme was also inhibited with the reduction of iron ion, resulting in the aggravated DNA damage in tumor cells. Our findings showed MFLs@5-ALA/DFO had potential to be applied for enhanced PDT of 5-ALA.