A novel lipid-based nanomicelle of docetaxel: evaluation of antitumor activity and biodistribution

PURPOSE: A lipid-based, nanomicelle-loaded docetaxel (M-DOC) was designed and characterized. Optical imaging was employed to evaluate the pharmacokinetics and antitumor efficacy of docetaxel in vivo. MATERIALS AND METHODS: The M-DOC was prepared using the emulsion-diffusion method. Transmission electron microscopy and dynamic light scattering were used to assess the morphology and particle size of the M-DOC. Critical micelle concentrations, their stability under physiological conditions, and their encapsulation efficiency – as measured by high-performance liquid chromatography – were assessed. Pharmacological features were evaluated in two different animal models by comparing M-DOC treatments with docetaxel injections (I-DOC). Bioluminescence imaging was used to assess antitumor activity and docetaxel distribution in vivo, using nude mice injected with luciferase-expressing MDA-MB-231 human breast tumor cells. In addition, animals injected with B16 melanoma cells were used to measure survival time and docetaxel distribution. RESULTS: The M-DOC was prepared as round, uniform spheres with an effective diameter of 20.8 nm. The critical micelle concentration of the original emulsion was 0.06%. Satisfactory encapsulation efficiency (87.6% ± 3.0%) and 12-hour stability were achieved. Xenograft results demonstrated that the M-DOC was more effective in inhibiting tumor growth, without significantly changing body weight. Survival was prolonged by 12.6% in the M-DOC group. Tumor growth inhibitory rates in the M-DOC and I-DOC groups were 91.2% and 57.8% in volume and 71.8% and 44.9% in weight, respectively. Optical bioluminescence imaging of tumor growths yielded similar results. Area under the curve((0–6 hour)) levels of docetaxel in blood and tumors were significantly higher in the M-DOC group (15.9 ± 3.2 μg/mL(−1), 601.1 ± 194.5 μg/g(−1)) than in the I-DOC group (7.2 ± 1.7 μg/mL(−1), 357.8 ± 86.2 μg/g(−1)). The fluorescent dye 1,1-dioctadecyl-3,3,3,3′-tetramethylindotricarbocyanine iodide mimicked M-DOC in optical imaging, and accumulated more in tumors in comparison with I-DOC. CONCLUSION: These results suggest that the lipid-based nanomicelle system was effective in inhibiting tumor growth, with little toxicity. Moreover, we have developed a noninvasive optical imaging method for antitumor drug evaluation, which merits further analysis for potential clinical applications.