Co-delivery of curcumin and piperine in zein-carrageenan core-shell nanoparticles: Formation, structure, stability and in vitro gastrointestinal digestion

Core-shell biopolymer nanoparticles were fabricated using a hydrophobic protein (zein) as the core and a hydrophilic anionic polysaccharide (iota-carrageenan) as the shell. The outer layer was physically cross-linked using cationic calcium ions to form salt bridges between the anionic carrageenan molecules. The potential of using these core-shell nanoparticles to co-deliver two important nutraceuticals (curcumin and piperine) was also investigated. A combination of electrostatic attraction, hydrogen bonding, and hydrophobic interactions was shown to be responsible for the assembly of the curcumin-piperine-loaded nanoparticles. Low levels of calcium ions (0-2 mM) led to the formation of small nanoparticles with compact structures, whereas higher levels (2-5 mM) promoted particle aggregation. The structural organization and morphology of the core-shell nanoparticles also depended on calcium levels, as seen by changes in circular dichroism, fluorescence spectroscopy, and electron microscopy. The core-shell nanoparticles were shown to be effective at retarding the photo- and thermal-degradation of the encapsulated curcumin and piperine. In addition, the core-shell nanoparticles could delay the release of the nutraceuticals under in-vitro gastrointestinal conditions, which may improve their oral bioavailability. In summary, core-shell nanoparticles assembled from zein and iota-carrageenan may be effective co-delivery systems for curcumin and piperine.