In Vitro Cytotoxic Activity and Binding Properties of Curcumin in the Presence of β-Casein Micelle Nanoparticles

Curcumin (CUR) is the active curcuminoid with many physiological, biochemical, and pharmacological properties. Solubility and stability of CUR is the limiting factors for realizing its therapeutic potential. Bovine β-casein is an abundant milk protein that is highly amphiphilic and self-assembles into stable micellar nanoparticles in aqueous solution. β-Casein nanoparticle can solubilize CUR molecules. In the present study, we introduced a drug-delivery system comprising hydrophobic anticancer drug, CUR, entrapped within β-casein-based nanoparticles. The interaction of CUR with β-casein was investigated using steady-state fluorescence spectroscopy and molecular docking calculation. Results showed that at pH 7, CUR molecules bind to β-casein micelle and formed complexes through hydrophobic interactions. Förster energy transfer measurements and molecular docking studies suggested that CUR molecules bind to the hydrophobic core of β-casein. The binding parameters including number of substantive binding sites and the binding constant were evaluated by fluorescence quenching method. Additionally, the cytotoxicity of free CUR and CUR-β-casein complex to human breast cancer cell line MCF7 was evaluated in vitro. The study revealed that the CUR-β-casein complex exhibited better cytotoxic effects on MCF7 cells compared to equal dose of free CUR.