Solid Lipid Nanoparticles and Nanostructured Lipid Carriers (SLNs and NLCs)
The SLNs and NLCs are basically composed of lipids as the inner phase (solid or solid and liquid), surface active materials (emulsifiers), and water. The nanoparticles are formed by congealing. The vitamins are entrapped in a solid state lipid that has a high stability. However in NLCs, the matrix is a combination of solid and liquid lipids so that it can accommodate more bioactive compounds due to the increased space between the solid state lipids (Aditya & Ko, 2015; Ekambaram, Sathali, & Priyanka, 2012; Livney, 2015).
Couto, Alvarez, and Temelli (2017) incorporated vitamin B2 in the SLN systems made of fully hydrogenated canola oil. Four variables (pressure, vitamin concentration, molecular weight, and stabilizer concentration) were studied according to their effects on encapsulation efficiency and loading efficiency. All in all, the optimal circumstances were pressure of 15 MPa, 2% vitamin concentration, 5% polyethylene glycol (PEG) with a molecular weight of 35,000 Da and the experiments revealed that high concentration of water-soluble compounds can be incorporated in SLN networks.
Genc, Kutlu, and Giiney (2015) successfully incorporated vitamin B12 in the matrix of an SLN system and analyzed the cytotoxicity of the entrapped vitamin on two control cell lines (H-Ras 5RP7 and NIH/3T3). Consequently, the results revealed the enhanced anticarcinogenic effect of prepared SLN system in comparison with the free vitamin form. Also, the characterization tests showed that the size of vitamin B12-loaded SLN structures was about 200 nm that raised the reaction rates and elevated the release efficiency.
Uraiwan and Satirapipathkul (2016) used the fat from Rambutan seed (Nephelium lappaceum) to fabricate NLCs together with Tween 20 and vitamin E as emulsifier and core material, respectively. The aim was to detect the stability of nanoparticles in accordance with the employed surfactant level. As a result, 5% (w/w) of Tween 20 was considered as the optimal concentration and formed a stable NLC system with an average particle diameter of 139.43 6 1.15 nm along with a polydispersity index of about 0.165 6 0.017.
Pezeshki, Ghanbarzadeh, Mohammadi, Fathollahi, and Hamishehkar (2014) prepared vitamin A palmitate-loaded NLC structures via the hot homogenization procedure. Precoil was implemented as the solid lipid, octy- loctanoate as the liquid phase, and poloxamer as the surfactant. To sum up, the lowest particle size was obtained in the presence of 6% poloxamer, also the encapsulation efficiency was about 98.5% and the shelf life of the formulation was 2 months at 25°C.