Effect of distribution of solid and liquid lipid domains on transport of free radicals in nanostructured lipid carriers

- Effect of solid and liquid lipid on distribution of encapsulant in NLC was studied.
- In NLC with less liquid lipid, encapsulant was localized in liquid lipid regions.
- Homogenous distribution of encapsulant was found in NLCs with more liquid lipid.
- Uniform distribution of the encapsulant reduced peroxyl radical transport rate in NLC.
- 100% liquid emulsion may be better at protecting encapsulated material than NLC.

Peroxyl radical sensitive fluorescent dye (BODIPY 665/676) encapsulated nanostructured lipid carriers (NLCs) were prepared by blending solid (eicosane) and liquid (glyceryl trioctanoate) lipid in various proportions (10:90, 30:70, 50:50, 100:0 liquid: solid). Peroxyl radical transport rate was measured by adding 20 mmol/l 2,2′-azobis-2-methyl-propanimidamide, dihydrochloride in the aqueous phase. Fluorescence imaging of NLCs revealed that fluorescent dye was distributed in the liquid lipid regions of 10 and 30% NLCs. However, 50% NLC resembled NLCs with 100% liquid lipid in that, little or no solid domains were observed and the dye was more or less uniformly distributed. Peroxyl radical transport was in the order, 100% < 50% <30% < 10% NLCs. More uniform distribution of the encapsulant possibly reduced the effective peroxyl radical transport rate, particularly when solid domains were present in the core of NLCs. Thus, 100% liquid lipid emulsions may be better than NLCs in improving the oxidative stability of the encapsulant.