Stabilization and Sustained Release of Fragrances Using Silk-PEG Microspheres

Fragrances, which are commonly used in food, textiles, consumer products, and medical supplies, are volatile compounds that require stabilization and controlled release due to their sensitivity to environmental conditions such as light, oxygen, temperature, and humidity. Encapsulation in various material matrices is a desired technique for these purposes, and there is a growing interest in using sustainable natural materials to reduce environmental impact. In this study, fragrance encapsulation in microspheres made from silk fibroin (SF) was investigated. Fragrance-loaded silk fibroin microspheres (Fr-SFMSs) were prepared by adding fragrance/surfactant emulsions to silk solutions, followed by mixing them with polyethylene glycol under ambient conditions. The study investigated eight different fragrances, where citral, beta-ionone, and eugenol showed higher binding affinities to silk than the other five fragrances, resulting in better microsphere formation with uniform sizes and higher fragrance loading (10-30%). Citral-SFMSs showed characteristic crystalline β-sheet structures of SF, high thermal stability (initial weight loss at 255 °C), long shelf life at 37 °C (>60 days), and sustained release (∼30% of citral remained after incubation at 60 °C for 24 h). When citral-SFMSs with different sizes were used to treat cotton fabrics, about 80% of the fragrance remained on the fabrics after one wash, and the duration of release from the treated fabrics was significantly longer than that of control samples treated with citral alone (no microspheres). This method of preparing Fr-SFMSs has potential applications in textile finishing, cosmetics, and the food industry.