Preparation and characterization of monomethoxy poly(ethylene glycol)-poly(ε-caprolactone) micelles for the solubilization and in vivo delivery of luteolin

Luteolin (Lu) is one of the flavonoids with anticancer activity, but its poor water solubility limits its use clinically. In this work, we used monomethoxy poly( ethylene glycol)-poly(epsilon-caprolactone) (MPEG-PCL) micelles to encapsulate Lu by a self-assembly method, creating a water-soluble Lu/MPEG-PCL micelle. These micelles had a mean particle size of 38.6 +/- 0.6 nm (polydispersity index = 0.16 +/- 0.02), encapsulation efficiency of 98.32% +/- 1.12%, and drug loading of 3.93% +/- 0.25%. Lu/MPEG-PCL micelles could slowly release Lu in vitro. Encapsulation of Lu in MPEG-PCL micelles improved the half-life (t(1/2); 152.25 +/- 49.92 versus [vs] 7.16 +/- 1.23 minutes, P = 0.007), area under the curve (0-t) (2914.05 +/- 445.17 vs 502.65 +/- 140.12 mg/L/minute, P = 0.001), area under the curve (0-infinity) (2989.03 +/- 433.22 vs 503.81 +/- 141.41 mg/L/minute, P = 0.001), and peak concentration (92.70 +/- 11.61 vs 38.98 +/- 7.73 mg/L, P = 0.003) of Lu when the drug was intravenously administered at a dose of 30 mg/kg in rats. Also, Lu/MPEG-PCL micelles maintained the cytotoxicity of Lu on 4T1 breast cancer cells (IC50 = 6.4 +/- 2.30 mu g/mL) and C-26 colon carcinoma cells ( IC50 = 12.62 +/- 2.17 mu g/mL) in vitro. These data suggested that encapsulation of Lu into MPEG-PCL micelles created an aqueous formulation of Lu with potential anticancer effect.