A new drug nanocrystal self-stabilized Pickering emulsion for oral delivery of silybin

A new silybin nanocrystal self-stabilized Pickering emulsion (SN-SSPE) has been developed using a high pressure homogenization method to improve the oral bioavailability of silybin. Influences of homogenization pressure and drug content on the formation of SN-SSPE were studied. The morphology, structure and size of Pickering emulsion droplets were characterized using a scanning electron micrograph, confocal laser scanning microscopy and atomic force microscopy. The stability, in vitro release and in vivo oral bioavailability of SN-SSPE were investigated. Results indicated that the particle size of silybin nanocrystals (SN-NC) decreased when homogenization pressure increased until 100 MPa. When the content of silybin reached 300 mg or above, a stable Pickering emulsion of silybin could be formed by sufficient SN-NC covering surfaces of oil droplets completely and thus self-stabilizing the Pickering emulsion. The emulsion droplet of SN-SSPE with the size of 27.3 ± 3.1 μm showed a core–shell structure consisting of a core of oil and a shell of SN-NC. SN-SSPE has shown high stability over 40 days. The in vitro release rate of SN-SSPE was faster than silybin coarse powder and similar to silybin nanocrystalline suspension (SN-NCS). The peak concentration of silybin of SN-SSPE following intragastric administration in rats was increased by 2.5-fold and 3.6-fold compared with SN-NCS and silybin coarse powder, respectively. The AUC of SN-SSPE was increased by 1.6-fold and 4.0-fold compared with SN-NCS and silybin coarse powder, respectively. All these results showed that the Pickering emulsion of silybin could be stabilized by nanocrystals of silybin itself and increased the oral bioavailability of silybin. The drug nanocrystalline self-stabilized Pickering emulsion was a promising oral drug delivery system for poorly soluble drugs.