Preparation and characterization of monocaprate nanostructured lipid carriers

Solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC) are potential drug delivery systems based on solid lipids. Although both carrier types are based on solid lipids, SLN consist of pure solid lipids while NLC are made of a solid matrix entrapping liquid oil. In the present paper, aqueous dispersions of SLN and NLC were successfully prepared by an oil-in-water microemulsion technique using monocaprate (MC) as the solid lipid, medium chain triglyceride (MCT) as the liquid oil and polyethylene glycol sorbitan monooleate (Tween 80) as the emulsifier. The present work aimed to modify the inner structure of an SLN by inducing liquid oil into the system to form an NLC, and then to investigate these new carriers in detail. Several methods including dynamic light scattering (DLS), environmental scanning electron microscopy (ESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectra were applied to characterize the particle size, morphology and structure of the NLC and SLN. DLS data showed that the average diameters of the SLN were ∼42 nm and the diameters of the NLC ranged from ∼25 to ∼120 nm. All samples had polydispersity indexes about 0.27. Using ESEM and TEM, SLN and NLC were observed to be nearly spherical particles. XRD, DSC and FTIR measurements revealed that imperfect crystallization occurred in the inner core of the NLC particles. The results suggest that nanostructured lipid carriers can be produced by this microemulsion method, and incorporation of the liquid oil into the SLN may affect their encapsulation capacity.