The objective of this study was to compare the charge effect of methyl
myristate loaded in neutral (Brij 72/
cholesterol at 7:3), cationic (Brij 72/
cholesterol/
dimethyl dioctadecyl ammonium bromide at 7:3:0.65) and anionic
niosomes (Brij 72/
cholesterol/
dicetyl phosphate at 7:3:0.65) for physicochemical characteristics, cytotoxicity in fibroblasts and B16F10
melanoma cells as well as melanogenesis induction activity. The maximum loading and percentage entrapment of methyl
myristate were 4.5, 90.68 +/- 7.95 in neutral; 11.0, 92.54 +/- 6.32 in cationic and 0.1% w/w, 74.43 +/- 1.86% in anionic
niosomes, respectively. All methyl
myristate loaded
niosomes were in unilamellar structure under transmission electron microscope and in nanosize at initial and after 3-month storage. The percentages of methyl
myristate remaining in all
niosomes kept at 4 +/- 2, 30 +/- 2 and 45 +/- 2 degrees C for 3 months were about 82, 74 and 72%, respectively, while the dry free methyl
myristate indicated 97.82 +/- 1.74, 96.56 +/- 2.91 and 91.39 +/- 4.32%, respectively. Blank neutral, blank cationic and methyl
myristate loaded neutral and cationic
niosomes exhibited moderate cytotoxicity in fibroblasts and B16F10
melanoma cells at 56.64 +/- 3.19, 59.72 +/- 1.51; 73.81 +/- 2.86, 82.51 +/- 0.20; 47.34 +/- 2.13, 52.67 +/-2.78 and 73.20 +/- 3.49, 84.34 +/- 2.75% cell viability, respectively. Blank anionic and methyl
myristate loaded anionic
niosomes indicated no cytotoxicity in both cells. Cytotoxic ratio of cell viability in normal and
cancer cells of all
niosomes indicated no toxic effect to normal cells. Methyl
myristate loaded cationic
niosomes demonstrated the highest
melanin induction with
tyrosinase activity of 1.42 and 1.70 folds of the control and 1.14 and 1.59 folds higher than
theophylline, respectively. This study has suggested the potential of methyl
myristate loaded cationic
niosomes for canities treatment.