Fabrication of protein nanoparticles and microparticles within water domains formed in surfactant-oil-water mixtures: Phase inversion temperature method

Protein nanoparticles and microparticles can be formed using numerous fabrication methods. In this study, a templating method was developed that involves trapping globular proteins within the aqueous domains formed by surfactant-oil-water (SOW) mixtures, and then inducing protein aggregation and particle formation through thermal denaturation. A heat-set gelling protein (whey protein isolate) was located in the aqueous phase of an oil-in-water nanoemulsion formed by spontaneous emulsification. This system was then heated to promote the conversion of the oil-in-water nanoemulsion into a bicontinuous microemulsion at the phase inversion temperature (PIT) or a water-in-oil emulsion above the PIT. In principle, the nature of the aqueous domains present in the SOW system when the protein molecules unfold and aggregate determine the size and morphology of the protein particles formed. In this study, turbidity, rheology, and confocal fluorescence microscopy measurements were used to show that spheroid protein particles (1-10 mu m) could be formed by heating SOW mixtures to a temperature above the PIT (which led to the formation of W/O emulsions) and where protein denaturation and aggregation occurred. This approach offers an alternative to existing methods of fabricating protein nanoparticles and microparticles suitable for utilization in the food and other industries. The major disadvantages of the method are that appreciable amounts of surfactant and oil are required in the particle-templating process, and that elevated temperatures are required to induce phase inversion and thermal denaturation. (C) 2015 Elsevier Ltd. All rights reserved.