Nanostructured lipid carrier-based gels for nutraceutical delivery: A colloidal perspective beyond traditional...

Development of structured lipid-based delivery systems is driven by the fact that the distribution of lipophilic bioactives is often limited by low gastrointestinal bioaccessibility, chemical instability and poor water solubility. Nanostructured lipid carriers (NLCs) are a versatile nanoscale platform and their incorporation into gel networks leads to hierarchical NLC-GEL architectures with different structural and functional properties than those of traditional emulsion gels. NLC-GELs are composed of nanoparticles with partially crystalline solid-liquid lipid matrices within a 3D gel network that offers extra structural factors such as lipid crystallinity and polymorphism, nanoparticle-matrix interactions and interfacial properties which can regulate gastrointestinal digestion and bioactive release as opposed to traditional emulsion gels which usually have liquid oil droplets trapped in a gel matrix. This study provides a critical discussion of recent developments in NLC-GEL systems in terms of formulation approaches, colloidal interactions, hierarchical structure, gastrointestinal behavior and their implications on bioactive delivery. Particular attention is paid to the relationships between NLC composition, lipid organization, interfacial properties, gel-network architecture, digestion, release, and bioaccessibility, since all these factors influence the performance of NLC-GELs. Improvements in encapsulation efficiency, physical stability and controlled release of bioactive substances have been achieved thru recent advances in lipid composition, surfactant selection and gel network design. However, before NLC-GEL systems are widely used and commercialised, issues with long-term exposure, regulatory approval, scale-up, and interactions with food matrices need to be resolved.