PHYSIOLOGICAL RESPONSIVENESS OF EMULSIONS STABILIZED BY SILICA NANO-PARTICLES

Recently, various physical and chemical strategies to design emulsion droplet interfaces for improved emulsion performance have been explored. To date, studies have established that various food colloids, e.g. nano-particles (NPs) of starch, chitin and silica can be used to form novel Pickering emulsions with droplet coatings possessing unique barrier properties, significantly improved stability and suitability for oral consumption. However, scarce data exists on the underlying principles linking the structure and properties of the nano-particles and corresponding droplet interfaces to emulsion digestive fate. Thus, this study sought to produce novel Pickering emulsions (using fumed silica nano-particles¹) and characterize them and their responsiveness to bio-relevant conditions of the human gastrointestinal tract.

The production and characterization of six formulations of 5% (w/w) olive oil-in-water emulsions will be described in terms of droplet size, electrokinetic charge and appearance based on DLS and fluorescence microscopy. These findings show that over 1% (w/w) of silica NPs emulsions are required to form stable emulsions which is also quantitatively supported by accelerated analytical centrifugation experiments. Moreover, increasing the concentration of silica NPs was found to markedly increase emulsion viscosity, as determined by a Brookfield viscometer. Further, findings demonstrating emulsion responsiveness to varying pH (3-8), ionic strength (0-200mM NaCl), artificial saliva, bile (0-25mg/mL) and 2h of in vitro duodenal lipolysis will be presented. Unlike protein-stabilized emulsions, the stability of samples has been found to increase upon bile addition and to exhibit sedimentation under certain conditions rather than creaming. Overall, the insights of the study will help rationalize the development of silica-stabilized Pickering emulsions for pharmaceutical and food applications.