Introduction: Photodynamic therapy (PDT) is a therapeutic method using a photosensitizer that is activated by proper wavelength of light and molecular oxygen. Effective delivery of photosensitizer to target tumor cells that causes minimal damage to healthy cells is an important requirement in photodynamic therapy of cancer. Protoporphyrin IX (PpIX) induced endogenously by 5-aminolevulinic acid can be used as a photosensitizer to destroy photodynamically tumor cells. In this study biocompatible gold nanoparticles were used as a vehicle to deliver 5-aminolevulinic acid (5ALA) in intratumoral injection for selective and efficient in vivo photodynamic therapy of CT26 tumor model. Accumulation time in equivalent concentration of 5ALA and 5ALA-AU was compared with each other. Results: PpIX accumulation achieved the peak level at 3 and 5 h after intratumoral injection of 5ALA-AU and 5ALA, respectively and was completely eliminated within 24 h. Conclusions: It seems that 5ALA conjugated gold nanoparticles are not efficient on decrease of incubation time of 5ALA.

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