Supercritical impregnation as a feasible technique for entrapment of fat-soluble vitamins into alginate aerogels

• Supercritical impregnation of alginate aerogels with fat-soluble vitamins was made.
• The influence of different pressures and impregnation times was investigated.
• The time of impregnation was shown to be critical parameter for vitamins' loading.
• In-vitro dissolution testing for vitamin D3 showed controlled release over 6 h.

The use of supercritical fluids as solvents allows innovative processing applications that can overcome the limitations of organic solvents. Their suitable properties make them appropriate for applications in the pharmaceutical and food industries and even more as a tool for the entrapment of substances. The aim of the presented work was to entrap two substances: 2-methyl-1, 4-naphthquinone (vitamin K3) and cholecalciferol (vitamin D3) within alginate aerogels by using supercritical carbon-dioxide. Supercritical impregnation of aerogels is receiving increasing attention as a green technique for entrapping poorly water soluble substances. The entrapment of vitamin D3 is a huge challenge due to its very high sensitivity.Impregnation experiments were carried out at 150 and 200 bar and 40 °C. As the process was shown to be feasible for both vitamins, the adsorption isotherms were measured and fitted with the Langmuir model. The effects of pressure, vitamins' concentrations and the time of impregnation on the loaded aerogels were studied. The time of impregnation was shown to be the critical and more important parameter where the highest loadings were achieved after only 1 h of impregnation. The loaded aerogels were characterised using Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. Furthermore, in-vitro dissolution testing for vitamin D3 was performed and the controlled release of the vitamin over a time span of 6 h was achieved.