Lipid nanoparticles: Different preparation techniques, characterization, hurdles, and strategies for the production of solid lipid nanoparticles and nanostructured lipid carriers for oral drug delivery

The bioavailability of an orally administered drug primarily depends on its solubility in the GIT and its permeability across cell membranes. Also, a drug in solution form is preferred for conducting pharmacological, toxicological and pharmacokinetic studies during the drug development stage. Thus, poor water solubility not only limits a drug's biological application but also challenges its pharmaceutical development. The use of lipid nanoparticles (LNs) in pharmaceutical technology has been reported for several years due to its important in green chemistry for several reasons specifically for its biochemical as "green" materials and biochemical processes as green processes that can be very environmentally friendly. Also, the physiological/physiologically related lipids (GRAS) made LNs usually enhance the drug absorption in the GIT. Hence, the pathways for absorption, metabolism, and transportation are present in the body, which may contribute to a large extent to the bio-fate of the lipidic carrier. Moreover, the LNs improves the mucosal adhesion and increases their GIT residence time. The LNs with a solid matrix are two types: solid lipid nanoparticle (SLN) and nanostructured lipid carrier (NLC). Also, their hydrophobic core provides a suitable environment for entrapment of hydrophobic drugs to improve its bioavailability. This review highlights and discusses the simple and easily scaled-up novel SLN and NLC along with their different production techniques, hurdles, and strategies for the production of LNs, characterization, lyophilization and drug release. Also, this review summarizes the research findings reported by the different researchers regarding the different method of preparation, excipients and their significant findings.