METHODS: Eucalyptol, a monoterpene oxide active, was used to formulate the NLC-Eu by using high pressure homogenization technique. The physicochemical characterization of NLC-Eu was performed to assess its morphology, particle size, polydispersity index, and zeta potential. The in vitro cytotoxic effects of this encapsulated eucalyptol on human (MDA MB-231) and murine (4 T1) breast cancer cell lines were determined using the MTT assay. Additionally, acridine orange/propidium iodide assay was conducted on the NLC-Eu treated MDA MB-231 cells. The in vivo sub-chronic toxicity of the prepared NLC-Eu was investigated using an in vivo BALB/c mice model.

RESULTS: As a result, the light, translucent, milky-colored NLC-Eu showed particle size of 71.800 ± 2.144 nm, poly-dispersity index of 0.258 ± 0.003, and zeta potential of - 2.927 ± 0.163 mV. Furthermore, the TEM results of NLC-Eu displayed irregular round to spherical morphology with narrow size distribution and relatively uniformed particles. The drug loading capacity and entrapment efficiency of NLC-Eu were 4.99 and 90.93%, respectively. Furthermore, NLC-Eu exhibited cytotoxic effects on both, human and mice, breast cancer cells with IC50 values of 10.00 ± 4.81 μg/mL and 17.70 ± 0.57 μg/mL, respectively at 72 h. NLC-Eu also induced apoptosis on the MDA MB-231 cells. In the sub-chronic toxicity study, all of the studied mice did not show any signs of toxicity, abnormality or mortality. Besides that, no significant changes were observed in the body weight, internal organ index, hepatic and renal histopathology, serum biochemistry, nitric oxide and malondialdehyde contents.