Chitosan coated nanostructured lipid carriers (NLCs) for loading Vitamin D: A physical stability study

A nanostructured lipid carrier (NLC) has been developed as a loading system for Vitamin D (VD). The NLCs were obtained by melt-emulsification method and coated with chitosan (CHI) by electrostatic deposition. The lipids used in the formulations were selected in order to provide higher encapsulation efficiency. Thermophysical properties of particles were evaluated by differential scanning calorimetry; particle stability was characterized by size distribution, polydispersity index, zeta-potential and light backscattering. The coating over NLCs was carried out by potentiometric titration with CHI at concentrations of 1.0, 1.5, 2.0 and 2.5% (w/v). Stearic (SA) and oleic acids (OA) were the lipids that showed higher compatibility with VD. The NLC 70(SA):30(OA) was the particle with the lowest polydispersity, size variation and less tendency to physical instability during the storage time. This formulation also presented encapsulation efficiency higher than 98%. In the particles coating, CHI adsorption into the colloidal dispersion provided an initial electrostatic stabilization of the system. A long-term steric barrier was established through further incorporation of CHI. Coated NLCs showed a core-shell structure and a positive zeta-potential (+30 mV), remaining stable for 60 days at 25 °C. During storage time, no expulsion of VD out of the particle was observed.