Nanocrystal-Loaded Lipid Carriers for Improved Oral Absorption and Anticancer Efficacy of Etoposide: Formulation Development, Transport Mechanism, In Vitro and In Vivo Evaluation

To improve the oral absorption and anticancer efficacy of the BCS-IV drug etoposide (ETO), oral nanocrystal-loaded lipid carriers (Lipo@NCs) were developed in this study by modifying the BCS-IV drug nanocrystal with the lipid bilayer. The ETO-Lipo@NCs were prepared by the thin film hydration high-pressure homogenization method, and the core of positively charged ETO nanocrystals was prepared by the sonoprecipitation-high pressure homogenization method. The optimized ETO-Lipo@NCs were spherical particles with an average particle size of 220.3 +/- 14.2 nm and a zeta potential of -9.95 +/- 0.81 mV, respectively. The successful coating of a lipid bilayer on the surface of nanocrystals in ETO-Lipo@NCs was confirmed by several characterization methods. Compared to nanocrystals, the release rate and degree of Lipo@NCs in SIF were significantly decreased, indicating that the lipid bilayer can effectively prevent the rapid dissolution of core nanocrystals. ETO-Lipo@NCs demonstrated a significant improvement in the intestinal permeability and absorption of ETO in a single intestinal perfusion experiment. In the cells, ETO-Lipo@NCs showed enhanced cellular uptake and transepithelial transport compared with ETO nanocrystals. Pharmacokinetic analysis indicated that ETO-Lipo@NCs had a longer plasma half-life than ETO solution, and the oral bioavailability of ETO-Lipo@NCs was 1.96- and 10.92-fold higher than that of ETO nanocrystals and ETO coarse crystals, respectively. Moreover, the ETO-Lipo@NCs orally dosed at 10 mg/kg exhibited an excellent inhibitory effect against tumors in a subcutaneous Lewis lung carcinoma (LLC) xenograft model compared with other preparations. These results indicate that the Lipo@NCs formulation has an oral absorption-promoting effect of the BCS-IV drug ETO, which could warrant further application in the oral delivery of other poorly bioavailable drugs.