Zein, a protein found in corn, can form nanoparticles that can be utilized in drug delivery systems. Condensed tannin and hydrolyzable tannin are high molecular weight plant polyphenols that interact strongly with protein, presumably by crosslinking via phenol-peptide hydrogen bonds. Adding a tannin “coat” to zein nanoparticles may protect the particles so they provide a stable drug delivery system. Our study sought to better understand how the chemical composition of the tannin preparation affected its interactions with zein nanoparticles. The nanoparticles were assessed using Dynamic Light Scattering to describe the size and dispersity of particles. Because zein has unusual solubility features, we first compared sonicating vs. gentle mixing to dissolve the zein in 70% ethanol. Sonication was quicker and produced smaller, more monodisperse particles. We then prepared nanoparticles using several different types of tannin, including condensed tannin from several sources and hydrolyzable tannins with different degrees of esterification. Our results suggest that the molecular weight and type of the tannin influence the Size of the nanoparticles, with coated particles smaller than uncoated particles.  Surprisingly, hydrolysable tannins destabilized the particles to digestion in an in vitro system.

Zein nanoparticles coated with various types of tannin

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