Abstract:

Objective Diacetate fiber is endowed with skin care function, distinctly improve its added value. Compared to traditional manufacturing processes, the supercritical CO₂ fluid technology (SCF-CO₂) is green, efficient and environmentally friendly since it solubilizes and carries the drug directly to the substrate to fabricate drug-loaded polymer without any solvent residue. In order to achieve the function to nourish skin it is important for the skin care diacetate fiber with good properties to release bioactive drug. Therefore, the influences of supercritical CO₂ fluid processing conditions on the release property of skin care diacetate fiber were investigated.

Method Resveratrol with antioxidant and antibacterial effects was utilized as the model drug. Resveratrol-loaded diacetate fiber was fabricated by SCF-CO₂ under different temperatures and different pressures. The resveratrol-loaded diacetate fiber was placed in the release medium ethanol to investigate the effects of fluid temperature (70, 80, 90 ℃) and pressure (12, 16, 20 MPa) on the release amount and the release rate of resveratrol from resveratrol-loaded diacetate fiber for the build-up of the release models.

Results When the SCF-CO₂ temperatures were 70, 80, 90 ℃ respectively, the loading capacity of resveratrol on diacetate fiber were 0.358 × 10^-4, 0.884 × 10^-4, 2.78 × 10^-4 g/g. It was found that the higher processing temperature of SCF-CO₂ resulted in the higher loading capacity. The absolute release amount and absolute release rate were increased along with the increasing loading capacity. The cumulative release percentage and the cumulative release rate were decreased when increasing SCF-CO₂ temperature(Fig. 1(c), Fig. 1(d)). About 40% resveratrol was remained in diacetate fiber when the release was in equilibrium under 90 ℃ of SCF-CO₂ temperature. When the releasing time was 40 min a rise for release rate was witnessed under 70, 80 ℃ of SCF-CO₂ temperature(Fig. 1(b), Fig. 1(d)), but the release rate rise appeared under 90 ℃ of SCF-CO₂ temperature 50 min into the release process. When the SCF-CO₂ pressures were 12, 16, 20 MPa respectively, the loading capacity of resveratrol on diacetate fiber were 0.592 × 10^-4, 0.884 × 10^-4, 2.177 × 10^-4 g/g. The higher processing pressure of SCF-CO₂ also resulted in the higher loading capacity. The corresponding absolute release amount and absolute release rate were also increased with increasing loading capacity. But when the release time is less than 50 min the absolute release amount and absolute release rate were higher under 12 MPa of SCF-CO₂ pressures. The cumulative release percentage and the cumulative release rate were decreased when increasing SCF-CO₂ pressure(Fig. 2(c), Fig. 2(d)). About 50% resveratrol was remained in diacetate fiber when the release was in equilibrium under 20 MPa of SCF-CO₂ pressure. When the releasing time was about 30 min or 40 min a rise for release rate appeared(Fig. 2(b), Fig. 2(d)). Compared to Higuchi model and Korsmeyer-Peppas model, the fitting degree of the first-order release model was the highest upon the release curve of resveratrol-loaded diacetate fiber (Fig. 3, Fig. 4), with R² above 0.93.

Conclusion The absolute release amount and absolute release rate depend on the loading capacity of resveratrol on diacetate fiber positively. The higher processing temperature and the higher processing pressure of SCF-CO₂ result in the higher loading capacity. The cumulative release percentage and the cumulative release rate show a downward trend with increasing SCF-CO₂ temperature and pressure. The reason is that more resveratrol is penetrated into the interior of diacetate fiber under the swelling of SCF-CO₂ to diacetate fiber. Moreover, the degree of swelling is strengthened with increasing SCF-CO₂ temperature and pressure. As a result, a large amount of resveratrol is remained in the diacetate fiber when the release reaches equilibrium. The release behavior of resveratrol from diacetate cellulose is found more aligned with the first-order release kinetic model.

Key words: supercritical CO₂ fluid, diacetate fiber, resveratrol, absolute release amount, slow release performance, release rate, release model