Protein corona formation around inorganic nanoparticles: Food plant proteins-TiO2 nanoparticle interactions

Powdered titanium dioxide (TiO 2 ) is used as a whitening agent in certain food products to enhance their optical properties. Food-grade TiO 2 (E171) contains a substantial proportion of nano-sized particles, which have been linked to adverse health effects. Plant-based foods are becoming increasingly popular in the human diet. For this reason, we examined the interactions between TiO 2 nanoparticles and a number of plant proteins: glutenin, gliadin, zein, and soy protein. All four proteins formed coronas around the TiO 2 nanoparticles, with the thicknesses of the adsorbed layers (4–60 nm) depending on the protein type. The morphologies of the protein coronas were elucidated using transmission (TEM) and scanning (SEM) electron microscopy. The surface potentials of the coated TiO 2 nanoparticles also depended on protein type, changing from −18 mV to +22.6, +61.4, +18.9, and −15.6 mV for glutenin, gliadin, zein, and soy protein, respectively. Fluorescence quenching, circular dichroism and infrared spectroscopy confirmed that interactions occurred between the nanoparticles and plant proteins that altered their secondary structures. These findings show the importance of taking into account the interactions of ingested nanoparticles with ingredients in the surrounding food matrix, and provide a better understanding of the effect of nanoparticles on plant proteins. •Proteins can adsorb to nanoparticle surfaces and form ''protein coronas''. •The ability of plant proteins to form coronas around TiO 2 nanoparticles was studied. •Glutenin, gliadin, soy protein, and zein all formed protein coronas. •Protein adsorption altered the charge and size of the TiO 2 -protein coronas. •Adsorption to nanoparticle surfaces altered the conformation of the plant proteins.