Solid Lipid Nanoparticles and Nanostructured Lipid Carriers: Emerging Lipid Based Drug Delivery Systems

In the past decade, research in the area of nanodrug delivery has reached a new height with the advent of lipid based nanodrug delivery systems. Lipids being biocompatible and possessing diverse physicochemical properties have tremendous potential to enhance oral bioavailability of water insoluble drugs. Incorporation of a drug in lipid carriers is a smart approach to overcome problems related with conventional oral therapy. In recent years, two lipid based nanoparticles, namely solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) are widely explored. SLN are spherical nanoparticles with a drug-containing solid lipid core stabilized with surfactants and formulated mainly to improve bioavailability of the drug molecules. Despite several advantages of SLNs, their major drawbacks include limited drug loading, drug leakage, and crystallization during storage. These drawbacks were avoided or reduced by the development of a new generation of lipid nanoparticles, the NLC, wherein a solid lipid is blended with liquid lipid. Modulation of drug release was added advantage with NLC formulations. The present review focuses on production techniques, characterization, release characteristics, stability, toxicity and potential applications of SLNs and NLCs.