Solid lipid nanoparticles for delivery of Calendula officinalis extract

Solid lipid nanoparticles (SLN) composed of long-chain fatty acids (palmitic acid, stearic acid or arachidicacid), Epikuron 200 (purified phosphatidylcholine), and bile salts (cholate, taurocholate or taurodeoxy-cholate) have been prepared by dilution of a microemulsion. A total of five different systems wereprepared, and characterized by photon correlation spectroscopy, transmission electron microscopy,differential scanning calorimetry, and infrared spectroscopy. The SLN formulation showing optimal prop-erties (lowest size and polydispersity index and highest zeta potential) was obtained with stearic acidand taurodeoxycholate as cosurfactant. This formulation was loaded with Calendula officinalis extract, anatural compound used on ophthalmic formulations given its anti-inflammatory, emollient, and woundrepairing activity. Calendula-loaded SLN preparations were characterized in order to determine loadingcapacity and entrapment efficiency. In vitro cytotoxicity and wound healing efficacy of Calendula-loadedSLN compared to that of a free plant extract were evaluated on a conjunctival epithelium cell line WKD.Our results suggest that this SLN formulation is a safe and solvent-free Calendula extract delivery sys-tem which could provide a controlled therapeutic alternative for reducing disease-related symptoms andimproving epithelium repair in ocular surface.