Composition and Structure - Lipid Nanoparticles: Production, Characterization and Stability - page 10

Chapter 2
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 con-
ditions, 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 disper-
sion stability. Polymers are often used to form polymer-lipid cores in the produc-
tion 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, knowl-
edge 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 dis-
cussed in this chapter.

Keywords Composition · Lipids · Surfactants · Localization · Structure

2.1 Composition of Lipid Nanoparticles

SLNs are typically composed of solid lipid(s), surfactant(s), co-surfactant
(optional) and active ingredients (typically drugs). The lipids used in the pro-
duction of lipid nanoparticles are physiological lipids. Based on their structural