Solid lipid nanoparticles for sustained pulmonary delivery of Yuxingcao essential oil: Preparation, characterization and in vivo evaluation.

The objective of this study was to prepare solid lipid nanoparticles (SLNs) for sustained pulmonary delivery of Yuxingcao essential oil (YEO). Three YEO loaded SLNs (SLN-200, SLN-400 and SLN-800) with different particle size were prepared and separated following a high-shear homogenization technique using Compritol 888 ATO as lipid and polyvinyl alcohol as an emulsifier. The particle size, zeta potential, drug encapsulation efficiency and drug loading of the SLNs were determined to be between 171 and 812nm, -17.1 and -19.3mV, between 76.6 and 90.2% and between 2.34 and 3.12%, respectively whereas the in vitro release data showed that the SLNs led to sustained drug release up to 48h. In addition, the SLN suspensions after nebulization conferred the fine particle fractions (<5.4μm) of 67.4-75.8%. Following intratracheal administration to rats, YEO loaded SLNs not only prolonged pulmonary retention up to 24h, but also increased AUC values (15.4, 18.2 and 26.3μg/gh for SLN-200, SLN-400 and SLN-800, respectively) by 4.5-7.7 folds compared to the intratracheally dosed YEO solution and by 257-438 folds to the intravenously dosed YEO solution, respectively. The present results were the first to show that YEO loaded SLNs may sustain YEO inhalation delivery and improve local bioavailability, representing a promising inhalable carrier to attain once daily application.