Optimization of high pressure homogenization conditions to produce nanostructured lipid carriers using natural and synthetic emulsifiers.

Lipid-based nanoparticles are one of the most promising encapsulation technologies in the field of nanotechnology, and solid lipid nanoparticles were the first generation of such structures. The second generation of lipid nanostructures is the nanostructured lipid carriers (NLC), which are composed of lipid materials with different melting points (MP). High pressure homogenization (HPH) is one of the main methods used on an industrial scale to produce NLC, and the process conditions affect the characteristics and physical stability of the produced NLC. The objective of this study was to optimize the HPH process conditions (number of cycles and homogenization pressure) to produce NLC formulated with different emulsifiers. The pre-emulsion for producing NLC was composed of an aqueous phase (90 %) with a single emulsifier (ethoxylated sorbitan monooleate (Tween 80), sorbitan monostearate (Span 60), soy protein isolate (SPI), whey protein isolate (WPI), or enzymatically modified soy lecithin (SL) in a 2 % (w/w) proportion, and a lipid phase composed of glyceryl tristearate (TS) and glyceryl trioleate (TO) in a 40:60 (w/w) proportion, corresponding to a model system containing similar contents of saturated and unsaturated fatty acids. The influence of the homogenization pressure (HP) (500 to 900 bar) and the number of cycles (NC) (1 to 3) on the characteristics of the NLC was assessed separately for each emulsifier using a2-level full factorial design. The NLC were characterized by the particle size (PS), polydispersity index (PI), and zeta potential (ZP) at 24 h and 15 days after production. The results indicated that SL,Tween 80, and WPI promoted the production of NLC in the nanometric range (PS ranging from 136.00 to 277.17 nm) that were stable (ZP > |20 mV|) during 15 days of storage at 25 °C. Of all the process conditions, 700 bar and 2 cycles were the optimal conditions for producing NLC with the different emulsifiers used in this study.