Heat-induced self-assembly of zein nanoparticles: Fabrication, stabilization and potential application as oral drug delivery

In this study, zein colloidal particles were self-assembled in aqueous ethanol through thermal treatment at 70 °C. The effect of heating, ethanol ratio and initial protein content on the physiochemical characteristics of zein nanoparticles were investigated. Thermal treatment was a necessary step to prepare nanoparticles with finer size and more homogenous distribution. The particle size decreased from 443.3 to 185.5 nm with initially ethanol concentration from 55% to 90% (v/v), whereas was inversely proportional to increased zein concentration (ranging from 125.6 to 199.1 nm for 20–100 mg/mL zein). The thermal treatment along with ethanol removal during zein nanoparticle generation induced the re-distribution of amino acid residues on the particle surface as indicated by the Raman spectroscopy and internal sulfhydryl groups determination. To further improve the stability and functional properties of these nanoparticles, gum arabic and sodium alginate were deposited as a secondary layer on zein nanoparticles mainly driven by electrostatic attraction. Sodium alginate at a polysaccharide/protein weight ratio of 1:10 showed the best improvement on the pH and ionic stability. The findings of this research provide a promising strategy and basic knowledge on optimizing zein-based delivery systems for food and pharmaceutical applications.