Preparation, characterization and evaluation of selenite-loaded chitosan/TPP nanoparticles with or without zein coating

The selenite-loaded chitosan (CS) nanoparticles using tripolyphosphate (TPP) as a cross-linking agent with or without zein (a water insoluble corn protein) coating were prepared to obtain selenite supplement formulations with low toxicity and improved antioxidant property. Scanning electron microscopy observation showed selenite-loaded CS/TPP nanoparticles had a spherical shape with uniform diameter (100–300 nm). The results demonstrated that particle size, surface charge, encapsulation efficiency, and release profile could be modulated by fabricating conditions. After coated with zein, the particle size maintained nanoscale (200–400 nm) while encapsulation efficiency increased from 60% to 95%. The release profile was also prominently improved with zein coating, the released selenite reduced from 85% to 30% within 4 h in PBS. In simulated gastrointestinal condition with enzymes, 93% of selenite released from non-coated CS/TPP nanoparticles into gastric fluid, however, the releasing rate decreased to 46% after coated with zein. Moreover, due to high antioxidant activity of CS, the in vitro antioxidant properties of selenite-loaded CS/TPP nanoparticles were significantly enhanced, compared with pure selenite.