Isotretinoin-containing liposomes: obtention, characterization and in vitro cytotoxicity on leukemia cells

Retinoic acid (RA) is the main vitamin A-related compound capable of regulating cellular differentiation and growth. The use of retinoids for the treatment of cancer has increased, mainly for leukemia, neuroblastoma, prostate and lung tumors. Therapeutic uses of retinoids are limited due to severe adverse reactions, especially when administered systemically, and their very low aqueous solubility. The chemical instability of RA isomers [all-trans (tretinoin), 13-cis (isotretinoin) and 9-cis retinoic acid (alitretinoin)] leads to different pharmacokinetic and toxicity profiles. Encapsulating retinoids in colloidal carriers, such as liposomes, can modify their pharmacokinetics, increase the drug uptake into neoplasic cells and improve the stability of these compounds. Objectives: In this work, in vitro antiproliferative activity of isotretinoin was investigated when K-562 cells were exposed to the drug in its free form and encapsulated into liposomes . Material and Methods: Liposomes were prepared by hydration/sonication method and cell viability was determined by trypan blue exclusion assay after incubation of 1x106 cells/mL in 96 wells plates for 24, 48 and 72 hours in the presence of equimolar concentrations of either the free drug or associated to the nanocarriers. Results: Antiproliferative studies demonstrated that isotretinoin encapsulated into liposomes was able to promote higher cytotoxic activity on K-562 leukemia cells when compared to the free drug, in a dose dependent manner, at 24, 48 and 72 hours of exposure. The highest increase in cytotoxic activity was observed at 72 hours of incubation, with a 70% gain on the drug cytotoxic index. Conclusion: The liposomal formulation for isotretinoin described in this work is a promising delivery system for clinical therapy applications, optimizing its effectiveness with a significant gain in the cytotoxic activity for this drug.