Biodegradable self-assembled MPEG-PCL micelles for hydrophobic oridonin delivery in vitro

The great potential of oridonin (ORI) for clinical application in cancer therapy is greatly limited due to its poor water-solubility. The purpose of this study was to increase the water solubility of oridonin using monomethoxy poly(ethylene glycol)-poly(epsilon-caprolactone) (MPEG-PCL) as drug carrier. The ORI-loaded MPEG-PCL micelles were prepared by thin film hydration method. The obtained ORI-micelles could be lyophilized into powder form, which could be re-dissolved in water to form homogeneous solution. This study showed that ORI was successfully incorporated in the core-shell structure of MPEG-PCL micelles and maintained its anticancer activity. The average particle size was 25.55 +/- 0.10 nm and the mean zeta potential was -4.71 +/- 0.05 mV. The actual drug loading and encapsulation efficiency were 7.99 +/- 0.03% and 99.51 +/- 0.34%, respectively. ORI could be released from MPEG-PCL micelles in a sustained manner in vitro. The permeation profiles of ORI from ORI-micelles and ORI water saturated solution through excised mouse skin demonstrated that ORI-micelles showed much better transdermal penetration performance than ORI water saturated solution. The prepared ORI-micelles have great potential for both direct intravascular administration and being further developed as a transdermal drug delivery system in cancer chemotherapy.