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Cooperative effect of 5-aminolevulinic acid and gold nanoparticles for photodynamic therapy of cancer.

An enhanced capacity for protoporphyrin IX (PpIX) synthesis through 5-aminolevulinic acid (ALA) administration has been reported in cancer cells. We compared the effect of ALA and ALA combined with gold nanoparticles (ALA-AuNPs) for photodynamic therapy (PDT) on human cervical cancer cell line. Because PpIX after photoactivation produces reactive oxygen species (ROS), ALA-AuNPs combinations can enhance this production and then induce higher phototoxicity. With this aim, two different-sized AuNPs (14 and 136 nm, AuNP1 and AuNP2, respectively) were successfully synthesized and characterized by UV-visible spectrophotometry and transmission electron microscopy. AuNPs were combined with ALA to evaluate their cooperative action in the intracellular ROS production, cell viability, and cell death mechanism. Results showed that ALA-AuNPs combinations induced cell death via ROS-mediated apoptosis after PDT. When exposed to light at their resonance wavelength, AuNP2 combined with ALA result in cytotoxicity and cell injury in greater extension than ALA and ALA-AuNP1 combination.