Core-shell biopolymer nanoparticles were prepared using antisolvent precipitation to form surfactant-stabilized zein core nanoparticles and then electrostatic deposition to form an alginate shell. The particle yield was relatively high (95%). The nanoparticles had a core diameter of about 80 nm, a shell thickness of about 40 nm, and an electrical charge of about -21 mV (pH 4.0). The amount of alginate required to saturate the surfaces of the zein nanoparticles was 2.0 mg/m(2). The nanoparticle suspensions had relatively good stability to pH: the particles were stable to aggregation from pH 3 to 8, but aggregated at pH 2 due to loss of charge. They were also relatively stable to elevated ionic strengths: the particles were stable to aggregation up to 100 mM NaCl at pH 7.0 and up to 2.0 M NaCl at pH 4.0. The suspensions had good thermal stability at pH 7, i.e., no increase in particle size after heating at 90 degrees C for 120 min. Nevertheless, some particle growth was observed during heating at pH 4 for 2 h. The core/shell biopolymer nanoparticles fabricated in this study have potential to be used as nano-delivery systems for bioactive molecules in food and pharmaceutical formulations.