Preparation of oridonin nanocrystals and study of their endocytosis and transcytosis behaviours on MDCK polarized epithelial cells

CONTEXT: Oridonin (ORI) has obvious anticancer effects, but its solubility is poor. Nanocrystal (NC) is a novel nano-drug delivery system for increasing bioavailability for ORI. However, the endocytosis and transcytosis behaviours of oridonin nanocrystals (ORI-NCs) through epithelial membrane are still unclear. OBJECTIVES: ORI-NCs were prepared and characterized. The in vitro cytotoxicity and endocytosis and transcytosis process on Madin-Darby canine kidney (MDCK) monolayer were investigated. MATERIALS AND METHODS: Anti-solvent precipitation method was adopted in preparation of ORI-NCs. Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were adopted to explore crystallography of ORI-NCs. Sulforhodamine B (SRB) method was used to test the inhibition effect on proliferation of MDCK cells. Quantitative analysis by HPLC was performed to study the endocytosis and transcytosis of ORI-NCs and ORI bulk drug, and the process was observed by confocal laser spectrum microscopy (CLSM) and flow cytometry. RESULTS: The particle size of ORI-NCs was about 274 nm. The crystallography form of ORI was not changed after prepared into NCs. The dissolution rate of ORI-NCs was higher than pure ORI in 120 min. At higher concentrations (34, 84 and 135 μg/mL), ORI-NCs significantly reduced the cell viability compared with free ORI (p < 0.05, p < 0.01). ORI-NCs demonstrated higher endocytosis in MDCK cells than free ORI (p < 0.01). In the transport process, ORI-NC was taken up into cells in an intact form, and excreted out from basolateral membrane of polarized epithelial cells in an intact form. The internalization and transmembrane amount increased as a function of time. CONCLUSIONS: ORI-NCs transported through the MDCK monolayers in an intact form.