Optimal method of gold nanoparticle administration in melanoma-bearing mice.

The present study assessed different methods of administering gold nanoparticles (GNPs) using different formulations to determine which of the methods achieved optimal radiosensitization. Cells from the B16F10 mouse melanoma cell line were implanted in the femoral area of mice, assigned to one of the eight following groups: i) Control; ii) intravenous (IV) injection of polyethylene glycol (PEG)-binding GNPs (Peg-GNPs) alone; iii) direct intratumoral (IT) injection of Peg-GNPs alone; iv) radiotherapy (RT)-alone; v) Peg-GNP IV + RT; vi) Peg-GNP IT + RT; vii) naked GNP (N-GNPs) IV + RT; and viii) N-GNP IT + RT. Injection volumes of the Peg-GNPs (particle size, 15 nm; dose, 2.8 mg/ml) and N-GNPs (particle size, 15 nm; dose, 200 mg Au/cc) were 0.3 and 0.2 ml per mouse, respectively, for IV and IT. The femoral area was irradiated with a single dose of 10 Gy. To evaluate the effects of GNPs, the current study measured the changes in the tumor volume ratio to the initial tumor volume over time and observed the survival rate. Administration of GNPs with RT did not improve the suppression of tumor growth or survival to a statistically significant extent. The administration of Peg-GNPs alone indicated a slight tumor suppressing effect at the early stage. The current study was not able to confirm the radiosensitization effect of GNPs in melanoma-bearing mice with tumors that were large in comparison to previous studies. Further research is required to validate the radiosensitizing effect on large tumors.