Solid lipid nanoparticles coated with silk fibroin

Solid lipid nanoparticles (SLNs) composed of stearic acid (SA) and ceramide (Cer) were prepared by an emulsification and solidification method using sodium lauryl sulfate (an anionic surfactant) as a stabilizer. And then, the SLN was coated with silk fibroin (SF) under an acidic condition by an electrostatic interaction. The size was tens of nanometers to hundreds of nanometers, and the coat around SA/Cer SLN was observed on the TEM photos. Following the thermograms of the SLN with and without SF coating, two phases, of which crystalline structures were different from each other, existed in the SLN. In vitro skin permeation experiment, the flux of Cer in 24 h were about 26 μg/cm2/h with SLN without SF coating, and about 55 μg/cm2/h with SLN with coating. The SF coat of nanoparticles was positively charged, so it would strongly interact with negatively charged skins, enhancing the skin permeation of Cer.