Multicore silica microcapsules containing α-tocopherol for potential consumer product applications

Microencapsulation is an advanced technique for protecting and enhancing the processing, delivery and performance of sensitive active ingredients, such as lipid-soluble vitamins. The fabrication of microcapsules containing such materials in an efficient, cost-effective and environmentally-friendly manner remains an ongoing challenge. Multicore silica microcapsules containing α-tocopherol in their cores were fabricated through salt-induced destabilisation and subsequent agglomeration of silica nanoparticles in an oil-in-water-in-oil double emulsion template at room temperature. The primary emulsion was prepared using three different concentrations (5, 10 and 15 wt%) of the internal oil phase, i.e. a mixture of α-tocopherol and sunflower oil. The external oil phase for the secondary emulsion consisted of different concentrations of Span 80 (0, 0.5 and 1 wt%) in sunflower oil. The capsule core size does not change during storage, confirming the stability of cores within the microcapsules. Mechanical testing provides that the microcapsules containing the lowest concentration of internal oil (5 wt%) have the highest rupture force and nominal rupture stress due to the higher silica content of these microcapsules. The incorporation of Span 80 does not significantly change the adhesion of microcapsules to a Lorica Soft leather substrate, mimicking human skin. The microcapsules are designed to release their contents upon mechanical rupture induced by rubbing against skin. This work shows the potential of such microcapsules to be applied in a range of consumer products, such as cosmetics.