In vitro biological activities of anionic γ-Fe2O3 nanoparticles on human melanoma cells

Three magnetic fluid (MF) samples containing gamma-Fe(2)O(3) (maghemite) nanoparticles surface-coated with either meso-2,3-dimercaptosuccinic acid (DMSA), citric acid or lauric acid were prepared, characterized, and assessed for their cytotoxic potential on the human SK-MEL-37 melanoma cell line. Ultra-structural analysis was also performed using transmission electron microscopy (TEM). In vitro cytotoxicity was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The inhibitory concentration (IC(50)) derived from the sigmoidal dose response curve was 254 mu g-iron/mL (95% confidence interval 239-270 mu g-iron/mL) for lauric acid-coated nanoparticles. DMSA-coated nanoparticles did not exhibit a clear trend toward toxicity (IC(50) value is more than 2260 +/- 50 mu g-iron/mL) and the IC(50) value was about 433 +/- 14 mu g-iron/mL for citric-acid coated nanoparticles. The cytotoxic response correlated with both the hydrodynamic diameter and the zeta potential suggests that the chain length of the carboxylic acid of the coating species may influence metabolic cellular process. Also the assayed nanoparticles can be considered non-cytotoxic to human melanoma cells since IC(50) values are higher than plasma concentration usually observed in clinical use of contrast agents. Using TEM we verified that all assayed nanoparticles were internalized by cells through endocytic vesicles. Additionally, cells treated with lauric acid-coated nanoparticles at high concentration (588 or 840 mu g-iron/mL) displayed morphological features of apoptosis (surface blebbing, intense vacuolization and chromatin condensation) or a typical DNA ladder pattern when analyzed by TEM or agarose gel electrophoresis, respectively. Apoptotic events may be operative, suggesting a promising therapeutic application for the lauric acid-coated nanoparticle in the treatment of cancer cells.