Studies on Fragrance Delivery from Inorganic Nanocontainers: Encapsulation, Release and Modeling Studies

Controlled Thermal Release of L-Menthol with Cellulose-Acetate-Fiber-Shelled Metal-Organic Framework

Fragrances have been widely used in many customer products to improve the sensory quality and cover flavor defects. The key to the successful application of fragrance is to realize controlled fragrance release, which relies on the use of an appropriate carrier for fragrance. An ideal fragrance carrier helps to achieve the stable storage and controlled release of fragrance. In this work, a novel composite fragrance carrier with MIL-101 (Cr) as the fragrance host and cellulose acetate fiber (CAF) as the protective shell was developed. The encapsulation effect of MIL-101 (Cr) and the protective function of the CAF shell significantly improved the storage stability of L-menthol (LM). Only 5 wt % of LM was lost after 40 days of storage at room temperature. Encapsulated LM could also be effectively released upon heating due to the thermal responsiveness of CAF. In addition, the composite carrier was highly stable with neglectable Cr leaching under different conditions. The results of this work showed that the developed composite carrier could be a promising carrier for the thermally triggered release of fragrance.

Adsorption and controlled release of three kinds of flavors on UiO-66

Delivery systems for controlled release of fragrances are significantly essential in the flavor and fragrance industry due to a limited life span (premature evaporation and degradation) of fragrance compounds. Recently, several adsorption materials such as porous materials have been developed in delivery systems for targeted fragrance release. In this work, UiO-66, a member of metal-organic framework (MOF) family with high porosity and greater adsorbability, was selected as a prospective alternative to traditional porous adsorbents for controlled release of fragrances. Isophorone, eugenol, and β-ionone with strong aroma are widely used as perfume flavors, soap flavor, cosmetic flavors, and even as a food-flavoring agents, and were chosen as representative fragrances for adsorption and controlled release studies. The adsorption and release behavior of fragrances on UiO-66 was evaluated by high-performance liquid chromatography (HPLC). The UiO-66 with high surface area (1,076 m2/g) achieved effective storage and controlled release for isophorone, eugenol, and β-ionone. The adsorption rates of isophorone, eugenol, and β-ionone can reach 99.4%, 99.9%, and 60.2%, respectively. Additionally, the release of these fragrances from UiO-66 can sustain over 20 days. UiO-66 exhibited higher release rate over eugenol with desorption rates of 95.2% than that of β-ionone (52.6%) and isophorone (49.6%), respectively, suggesting a good adsorption-release selectivity of UiO-66 to different fragrances. This study further confirms the usability of UiO-66 in fragrance release and extends the application of MOF porosity in aroma release.

Halloysite Tubes as Nanocontainers for Herbicide and Its Controlled Release in Biodegradable Poly(vinyl alcohol)/Starch Film

Commercial herbicide atrazine (AT) was first loaded into the lumen of halloysite nanotubes (HNTs) in the amount of 9 wt %, and then the AT-loaded HNTs (HNTs-AT) were further incorporated into poly(vinyl alcohol)/starch composites (PVA/ST, with the weight ratio of 80/20) to construct a dual drug delivery system. AT loaded in nanotubes displayed much slower release from PVA/ST film in water than free AT; for example, the total release amount of AT from PVA/ST film with loaded AT was only 61% after 96 h, while this value reached 97% in PVA/ST film with free AT. The release behavior of AT from PVA/ST film with HNTs-AT was first dominated by the mechanism of matrix erosion and then by the mechanism of Fickian diffusion. In addition, combining HNTs and PVA/ST blends together in the controlled release of herbicide also reduced its leaching through the soil layer, which would be useful for diminishing the environmental pollution caused by pesticide.