Encapsulation of oil in silk fibroin biomaterials

Microencapsulation is becoming increasingly important in the food, cosmetics, and medicinal industries due to its potential for stabilization and delivery of volatile and delicate compounds. Novel food-safe techniques for encapsulating oil in silk biomaterials using emulsion-based processes that exploit silk's unique properties (including amphiphilicity, biocompatibility, aqueous and ambient processing, and tunable physical crosslinking behavior) are described. The sonication-induced self-assembly of silk previously applied to hydrogel fabrication replaced the use of the thermal or chemical suspension crosslinking traditionally used to stabilize the aqueous protein phase in emulsions. Stable, physically crosslinked silk micro- and macro-particles loaded with oil or water-soluble dye were produced by aliquoting sonicated silk solutions into an oil bath. Oil micro-droplets emulsified in aqueous silk solutions did not impede the self-assembly of silk into films or hydrogel networks. In O/W/O emulsions, particle morphology and silk permeability to a model lipophilic dye in the interior phase were controllable via processing. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014, 131, 39990.