Interfacial engineering strategy to improve the stabilizing effect of curcumin-loaded nanostructured lipid carriers

In this work, the interfacial structure of nanostructured lipid carriers (NLCs) stabilized by whey protein isolate (single layer NLCs, S-NLCs) was modified with polysaccharide through two approaches: 1) electrostatic deposition of a polysaccharide layer onto the surface of S-NLCs affording double layer NLCs (D-NLCs); 2) heating the protein-polysaccharide complexes to promote biopolymer assembly, which were utilized as emulsifiers for the composite layer NLCs (C-NLCs). S-NLCs presented a spherical shape, hydrodynamic diameter of about 300 nm and curcumin (Cur) encapsulation efficiency below 30%. However, these values changed following interfacial decoration of NLCs. The interfacial viscoelastic studies suggested that the type 2 strategy enabled a more compact and elastic stabilizing layer than the type 1 method, as the interfacial biopolymers of the former were held together by multiple interactions. Therefore, C-NLCs showed higher capacity to inhibit polymorphic transition or degradation of Cur than other NLCs. Both approaches could slow down the lipolysis rate as well as decrease the lipolysis degree of NLCs during simulated digestion, while increase the bioavailability of the entrapped Cur. Besides, the highest cellular antioxidant activity was observed for Cur in C-NLCs, followed by D-NLCs and S-NLCs, in accordance to the stabilizing effects of these NLCs for the loaded agent.