Composition and Structure

Abstract

Lipid nanoparticles, including solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLC), lipid-drug conjugates (LDC) and polymer-lipid hybrid nanoparticles (PLN), are colloidal carriers with a lipid matrix that is solid at body temperature. These colloidal carriers have attracted increasing interest for their use in therapeutic and cosmetic applications. The performance of lipid nanoparticle formulations is greatly influenced by their composition and structure. Lipid nanoparticles are generally composed of lipids, surfactants and co-surfactants. The lipid materials used in the production of lipid nanoparticles are usually solid at room temperature. Being well-tolerated in physiological conditions , lipid nanoparticles are typically biocompatible. Liquid lipids, or oils, are specifically used for production of NLCs. In most cases, lipid nanoparticles are produced as dispersions and surface-tailored with surfactants to improve dispersion stability. Polymers are often used to form polymer-lipid cores in the production of PLNs. Lipid nanoparticles are often used as sustained-release systems, with the structure of the lipid nanoparticles dictating their release properties. While the concentration of drug in lipid nanoparticle dispersions is quite well known, knowledge of the drug-lipid interaction in terms of the state and localization of the drug in the nanoparticle is still unknown. Several structural models of SLNs and NLCs have been proposed. The composition and structure of lipid nanoparticles-two critical factors that may influence their pharmaceutical performance-will be discussed in this chapter.