Solid lipid nanoparticles (SLNs) have gained recent interest as colloidal drug carriers due to their submicron size, potential for industrial production, and their physiological compositions. SLNs, firstly developed by Mu¨ller and Lucks (1996), consist of solid lipids which are dispersed in an aqueous surfactant solution and become solid at room temperature. The carrier has been used for effective controlled-release and prolonged stability of both lipophilic and hydrophilic drugs (Mu¨ller et al., 2000; Wissing and Mu¨ller, 2002; Ruktanonchai et al., 2008).