Calcium phosphate coated core-shell protein nanocarriers: Robust stability, controlled release and enhanced anticancer activity for curcumin delivery.

Composite protein and inorganic nanodelivery systems can realise a pH-responsive release and effectively improve the stability and anti-cancer proliferative activity of hydrophobic molecules. In this study, a novel core-shell structure of NaCas (Sodium Caseinate)@CaP (Calcium Phosphate) as a nanodelivery system with NaCas as the core for increasing solubility and CaP as the shell for enhanced stability was built. By using Cur (Curcumin) as a model bioactive molecule, (Cur@NaCas)@CaP nanoparticles (NPs) demonstrated a uniform size distribution of 150-200 nm with a distinct nano-composite structure. After exposure to 80 °C for 2 h, the NaCas@CaP loaded Cur still retained 80% stability while under the same conditions only 12% of free Cur remained intact. UV-light stability was remarkably enhanced 8.56 fold by the protection of the core-shell structure. More importantly, pH-responsive release was achieved owing to the CaP surface coating. The encapsulated Cur by NaCas@CaP NPs exhibited an enhanced cellular anti-oxidant activity (CAA) based on MGC-803 cell monolayer models. The confocal laser-scanning microscopy (CLSM) images and cancer-cell-proliferation assay illustrated that (Cur@NaCas)@CaP NPs showed significantly improvements of cellular uptake and anti-cancer activity against A549 cancer cells than free Cur. These novels core-shell NaCas@CaP NPs are very promising for intensifying the stability and bioactivity of hydrophobic compounds in drug delivery and cancer treatment.