Table 1. . Comparison between properties of solid lipid nanoparticles and nanostructured lipid carriers.

Properties	SLNs (developed since early 1990s)	NLCs (developed since early 2000s)
Drug encapsulation efficiency	Lesser drug encapsulation efficiency due to formation of highly ordered crystalline arrangement	Higher drug encapsulation efficiency as blend of solid lipids and liquid lipids form disordered structure providing higher space for drug loading Also due to high solubility of drug in liquid lipids
Shelf-life storage	Drug expulsion takes place during storage due to polymorphic transition of high-energy modification formed during fabrication to low-energy modification during storage	No polymorphic transition takes place and drug expulsion is prevented
Release rate	Slower release as mobility of drug in crystalline form is less	Faster release as mobility of drug in crystalline form is high

NLC: Nanostructured lipid carrier; SLN: Solid lipid nanoparticle.