Formulation of solid lipid nanoparticles and their applications

Abstract

Solid lipid nanoparticles (SLN) introduced in 1991 represent an alternative carrier system to traditional colloidal carriers, such as emulsions, liposomes and polymeric micro- and nanoparticles. SLN are aqueous colloidal dispersions, the matrix of which comprises of solid biodegradable lipids. SLN are manufactured by techniques like high pressure homogenization, solvent diffusion method etc. SLN combine advantages of the traditional systems but avoid some of their major disadvantages. They exhibit major advantages such as modulated release, improved bioavailability, protection of chemically labile molecules like retinol, peptides from degradation, cost effective excipients, improved drug incorporation and wide application spectrum. However there are certain limitations associated with SLN, like limited drug loading capacity and drug expulsion during storage, which can be minimized by the next generation of solid lipids, Nanostructured lipid carriers (NLC). NLC are lipid particles with a controlled nanostructure that improves drug loading and firmly incorporates the drug during storage. Due to their unique size-dependent properties, lipid nanoparticles offer the possibility to develop new therapeutics. Owing to their properties and advantages, SLN and NLC may find extensive application in topical drug delivery, oral and parenteral administration of cosmetic and pharmaceutical actives. Cosmeceuticals is emerging as the biggest application target of these carriers. Carrier systems like SLN and NLC were developed with a perspective to meet industrial needs like scale up, qualification and validation, simple technology, low cost etc. The ability to incorporate drugs into nanocarriers offers a new prototype in drug delivery that could be used for secondary and tertiary levels of drug targeting. This review mainly focuses on the advantages and limitations of the solid lipid nanoparticles over other colloidal carriers and different techniques available for the formulation of SLNs and their applications in therapeutics.