Solid lipid nanoparticles and nanostructured lipid carriers: a review of the methods of manufacture and routes of administration

The bioavailability of drugs is dependent on several factors such as solubility and the administration route. A drug with poor aqueous solubility, therefore, poses challenges with regards to its pharmaceutical advance and ultimately its biological usage. Lipid nanoparticles have been used in pharmaceutical science due to their importance in green chemistry. Their biochemical properties as 'green' materials and biochemical processes as 'green' processes mean they can be environmentally sustainable. Generally, lipid nanoparticles can be employed as carriers for both lipophilic and hydrophilic drugs. The proposed administration route for nanoparticles can present advantages and disadvantages which should be considered by a formulator. Solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) are attractive delivery systems because of their ease of manufacture, biocompatibility, biodegradability, and scale-up capacity of formulation constituents. The easy and simple scalability of novel SLNs and nano lipid carriers, along with their various processing procedures, recent developments, limitation and toxicity, formulation optimization and approaches for the manufacture of lipid nanoparticles, lyophilization and drug release are comprehensively discussed in this review. This review also summarizes the research data related to the various preparation methods and excipients used for SLNs and NLCs in recent years.