smartLipids^® as third solid lipid nanoparticle generation – stabilization of retinol for dermal application

smartLipids^® as the 3^rd lipid nanoparticle generation are made from a complex lipid mixture. The chaotic particle matrix structure provides higher loading with actives and a firmer inclusion inside the particle matrix being more protective for chemically labile molecules. Thus, these particles were used to develop an optimized retinol formulation. As a new approach, the old concept of the core-shell SLN particles was combined with the novel smartLipids^® technology as new stabilization model. Particles were produced by hot high pressure homogenization, loaded with increasing amounts of retinol (5%, 15%, 20%), and both the physical (size, crystallinity) and chemical stability were monitored. According to the core-shell model, the retinol precipitates first, forming a core. Then, in the final solidification stage of the particles the retinol core gets surrounded by a shell of lipid-retinol eutectic mixture. With increasing retinol content, more retinol precipitates in the core and is chemically protected. The model was confirmed by the stability data obtained, e.g. with 5%, 15% and 20% retinol loading, after 60 days of storage 37%, 59% and 75% of retinol remained in the particle suspensions. Thus, chemical stability increased with loading. Size remained unchanged at about 200 nm. Crystallinity showed absence of polymorphic transitions, which can cause expulsion of active from the particle matrix, leading to degradation. After incorporation of the particles into a gel as dermal formulation, similar stability was observed. The developed concept can be transferred to other chemically labile dermal actives, in cosmetics and pharma.