The skin is constantly exposed to harmful environmental factors, especially air pollution, which weakens its barrier function and increases oxidative stress. The antioxidant-rich microalgae Dunaliella species is being studied as a promising ingredient in dermocosmetic products designed to protect the skin from oxidative damage and strengthen the skin barrier. In the first part of our thesis, we studied its effects on a human keratinocyte cell line (NCTC2544), alongside microalgae Tetradesmus species and cyanobacterium Phormidium species for comparison. Furthermore, in the second part of the study, we examined advanced delivery systems such as liposomes and transferosomes, both with and without betamethasone dipropionate incorporated, a local corticosteroid commonly used in the treatment of inflammatory skin diseases. First, we performed a physical-chemical evaluation of these systems, which included determining particle size, polydispersity index, and zeta potential, thereby assessing the stability and technological properties of the formulations produced. We then examined their effect on the selected cell line. In both parts of the work, we performed a test to determine cell metabolic activity using the MTS reagent, which reflects the metabolic activity of living cells and is indirectly related to cell proliferation, and examined cell morphology using an inverted light microscope. In the evaluation of microalgae and cyanobacteria samples, cell proliferation of 100 % or more was achieved at all tested concentrations (1, 5, 10, and 15 µL/mL), with no significant differences between individual strains. Compared to the standard irritant (sodium dodecyl sulfate), where proliferation was noticeably lower (≤5.1 %), all tested samples were significantly more biocompatible. Cell morphology analysis confirmed these findings, as the cells maintained their characteristic growth and morphology without signs of damage. The liposomes and transferosomes produced exhibited suitable physicochemical properties and also proved to be biocompatible at all tested dispersion volumes (1–4 µL/well), both with and without betamethasone dipropionate incorporated. The incorporation of the corticosteroid slightly reduced cell proliferation, which we attribute to its antiproliferative effect. Liposomes (≥94.0 %) achieved slightly better results than transferosomes (≥88.3 %), but both formulations showed significantly higher cell proliferation compared to the standard irritant (≤3.8 %). Microscopic analysis of cell morphology also confirmed preserved growth and characteristic cell shape without signs of damage.
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