The field of nanotherapeutics is the application of nanotechnology to medicine and drug development.
LNPs are produced using high pressure homogenization (HPH), solvent emulsification/evaporation, supercritical fluid extraction of emulsions (SFEE), ultrasonication or high speed homogenization and spray drying. Hot or cold processes are used for HPH.
Liposomes were invented in 1965 and are defined as spherical vesicles with an internal cavity that is aqueous surrounded by a lipid bilayer membrane. The term liposome comes from the Greek words ‘lipid’ and ‘soma’, meaning fat and body. The advantages of liposomes as pharmaceutical carriers include protection of the drug against enzyme degradation, low toxicity, flexibility, biocompatibility, biodegradability and non-immunogenicity. Disadvantages include short shelf life, poor stability, low encapsulation efficacy, rapid removal by the reticulodendothelial system, cell interactions or adsorption and intermembrane transfer. Pharmaceutical liposomes are also expensive.
Nanostructured lipid carriers (NLCs) are modified SLNs with improved stability and loading capacity. NLCs differ from SLNs by composition of the solid matrix and they have improved stability, capacity loading and prevent drug expulsion during storage.
SLNs and NLCs have an average size of 40-1000 nm, spherical morphology and are composed of solid phase lipid and surfactant. The dispersed phase is solid fat and the surfactant is used as emulsifier. SLN lipid components are solid at body and ambient temperatures and may be highly purified triglycerides, complex glyceride mixtures or waxes. To enhance stability surfactants are used and the selection of lipids and surfactants can affect the physiochemical properties and quality including particle size and drug loading. Compared with liposomes, SLNs and NLCs have drug stability, prolonged release. They are safer than polymeric carriers due to avoidance of organic solvents for production. They are amenable to large scale production.