Characterization Methods for Solid Lipid Nanoparticles (SLN) and Nanostructured Lipid Carriers (NLC)

Solid lipid nanoparticles (SLN) and the next generation of nanostructured lipid carriers (NLC) seem to be a very promising alternative to other colloidal carriers, such as liposomes, microemulsions, and polymeric nanoparticles. These combine the advantages of the cited nanocarriers and can improve the dissolution rate in biological fluids, increase the drug absorption, improve the tissue distribution in the target organ, enhance the drug bioavailability and ensure controlled drug release. SLN and NLC can ensure higher drug stability in the harsh environment, cover the bitter taste of the drug, and reduce the first-pass effect after oral administration. However, these carriers suffer from some disadvantages such as low drug loading capacity, drug expulsion, and unpredictable gelation tendency.

This article aims to provide detail information about the process of complex characterization of SLN and NLC to produce an effective, quality and safe colloidal DDS with desired properties, based on the literature published in the period from 2000 to 2017.

Characterization techniques in terms of size and particle size distribution; surface morphology, functionalization, and zeta potential; structure, depending on the degree of crystallinity, lipid modification, drug incorporation and loading capacity; drug release; co-existence of other nano- and microstructures; and toxicity assessment according to the process of production, lipids and surfactants used and route of administration are discussed in the article.

The precise characterization of lipid nanocarriers as drug delivery systems ensures guarantees for the quality of the product as an effective and safe form. The typical composition of SLN and NLC requires a comprehensive approach of characterization and in-depth analysis of the results to perform a drug delivery system with desired properties.