Self-Assembly of Protein Nanoparticles from Rice Bran Waste and Their Use as Delivery System for Curcumin

Rice bran waste, a massive byproduct from rice milling, is rich in proteins, lipids, vitamins, and trace minerals. However, rice bran is an underutilized sustainable resource that is ultimately discarded as agricultural waste. Herein, rice bran albumin (RBA) was extracted from rice bran waste using water, and its properties of amino acid compositions, molecule weight, secondary structure, denaturation temperature, and ζ-potential were characterized. The results indicated that RBA possessed negative charges and amphiphilic molecules with high value and good digestibility. RBA was then proposed to prepare nanoparticles with chitosan (CS) (RBA–CS nanoparticles) by a self-assembly method. The RBA–CS nanoparticles exhibited spherical shape with core (RBA)–shell (CS) structures, and the average size was about 384 nm. The solubility of curcumin (CUR) was greatly improved after loading into the RBA–CS nanoparticles, and higher entrapment efficiency (EE, 93.56%) was obtained. CUR released from the RBA–CS nanoparticles was governed by two distinct stages (burst release and sustained release) and dependent on the pH value of the release media. Diffusion, swelling, and erosion mechanisms might coexist for the full release processes for the RBA–CS nanoparticles. The RBA–CS nanoparticles have properties of delayed degradability in gastric conditions and complete digestibility in the small intestine with good biodegradability. Additionally, the CUR loaded RBA–CS nanoparticles exhibited higher cytotoxicity than free CUR for Caco-2 cells. Thus, a sustainable and higher value byproduct (RBA–CS nanoparticles) was obtained from rice bran waste, which has great potential application for hydrophobic active agent delivery.