In the work, the antioxidant activity of astaxanthin (AST) and the influence of the base formulation on the kinetics of AST release were studied. Three stable O/W AST-loaded emulsions, differing in droplet size (12.7 μm(E1), 3.8 μm(E2), 3.2 μm(E3)) and a nanoemulsion (0.13 μm, NE) were prepared. The results confirmed very strong antioxidant activity of AST. The emulsion internal phase droplet size did not significantly affect the AST release. The amount of released AST was respectively: 13.60% (E1), 11.42% (E2), 9.45% (E3), 9.71% (NE). The best fit to experimental data was obtained using the Higuchi model for emulsions and the Korsmeyer-Peppas model for NE. The results show that the AST release process is limited by the diffusion through carriers and the prepared O/W emulsions can be applied as vehicles for delivery of astaxanthin to the skin, ensuring effective anti-aging action of the cosmetics.

The process of obtaining alginate microspheres (AMs) by emulsification method was optimized by applying statistical analysis software. Ten batches of microspheres were prepared using the fractional plan 3 ^(K-p). AMs were obtained with two different methods: an ultrasonic homogenization (UH) process and a rotor-stator mechanical homogenization (MH). The amount of a cross-linking agent (CaCl ₂), calcium chloride rate addition, and the sonication amplitude (UH) or the speed of rotor rotation (MH) were selected as formulation variables. All the batches were evaluated in terms of stability and size of the alginate microspheres. Approximation profiles were developed. As a result of the conducted research, stable alginate microspheres with sizes ranging from 10 to 30 micrometres were obtained. The obtained results showed that the quality of AMs was mainly affected by the concentration and the rate of calcium chloride addition into the system. Therefore, the role of calcium ions in the mechanisms of shell structuring was discussed. Lactobacillus casei bacteria were encapsulated into the batches found to be optimum. The high encapsulation efficiency (EE) of the bacteria (72-94%) depending on the form) and their viability over time were obtained. The model developed in the study can be effectively utilized to achieve the AMs formulations.