Starch nanoparticles with brewers’ spent grain extract as stabilizers for Pickering emulsions: a biodegradable and sustainable alternative for natural cosmetics

Natural sources of bioactive compounds have been studied worldwide. This study highlight the potential benefits of Pickering emulsions, a novel method of stabilizing two immiscible phases without surfactants, when added with starch nanoparticles with brewers’ spent grain extract (BSG extract), evaluated by using a 2³ factorial design. The effects of starch nanoparticle concentration, oil/water ratio, and stirring time on the properties of Pickering emulsions were evaluated. The cytotoxicity of BSG extract was evaluated in 3T3 fibroblasts by the MTT and neutral red uptake (NRU) methods. It was demonstrated that, in both tests, the extract concentration considered safe (cell viability > 50%) was equal to or below 1 mg.mL1. The superior stirring time significantly reduced the particle diameters and the polydispersity index of the starch nanoparticles in the Pickering emulsion. Spherical starch nanoparticles were observed in the Pickering emulsions by scanning electron microscopy (SEM). The formulation with nanoparticle concentration of 2%, an oil/water ratio of 0.5/99.5, and a stirring time of 5 minutes (PE3), showed promising results. The safety in vitro of the Pickering emulsions was evaluated by the HET-CAM test, and no vascular signs were monitored for Pickering emulsions, proving the safety of the Pickering emulsion. The Pickering emulsions with the addition of starch nanoparticles with BSG extract can be a natural and safe option for biocosmetic formulation, facilitating the incorporation of antioxidant active ingredients.