Nanostructured lipid carriers and natural deep eutectic solvents: a highly advantageous combination for the encapsulation of curcumin

BACKGROUND Curcumin is a naturally derived polyphenol known for its potent biological properties. Its therapeutic potential, however, is hindered by low bioavailability. Nanostructured lipid carriers (NLCs) have emerged as advanced delivery systems to overcome such limitations. Natural deep eutectic solvents (NADESs) have garnered attention as green alternatives to conventional solvents with potential applications in drug delivery. In this context, this study explores the encapsulation of curcumin in NLCs incorporating a hydrophobic NADES (hNADES) as a multifunctional component, serving both as an alternative to conventional liquid lipids in the NLC formulation and as a green solvent for curcumin. RESULTS Curcumin exhibited satisfactory solubility in the hNADES (1.17 mg/mL at 25 °C; 4.79 mg/mL at 70 °C). The hNADES was successfully incorporated as the liquid lipid in curcumin‐loaded NLCs (CUR‐NLCs). The preparation of CUR‐NLCs was optimized through a Box–Behnken design. The CUR‐NLCs obtained via the optimized process had a size of 227.8 ± 17.4 nm, PDI of 0.318 ± 0.032, and ζ‐potential of −39.1 ± 2.3 mV. Encapsulation efficiency was 79.1 ± 0.9%, and process yield was 86.8 ± 1.1%. The ability of CUR‐NLCs to scavenge the DPPH free radical reached 42.4 ± 0.4% at 120 min, whereas free curcumin showed 15.3 ± 0.2%. Photoprotective performance also improved, with CUR‐NLCs exhibiting Sun Protection Factor (SPF) values up to 8.28 ± 0.02 and providing an SPF boost of 33.7% when incorporated into a base sunscreen. CONCLUSION The findings highlight the successful use of a hydrophobic NADES as a multifunctional liquid lipid component in the design of NLCs for curcumin encapsulation, underscoring the potential of hNADESs in the development of advanced lipid‐based formulations.