## 2 Results and Discussion
### Assessment of Cytotoxicity  
As part of the analyses, the tested hydrogels' effect on cell membranes' metabolic activity and integrity was assessed using the resazurin assay (AB assay) and the neutral red assay (NRU assay). Cytotoxicity was assessed on cells constituting various layers of the skin, BJ and HaCaT. The obtained results indicated significant differences in cytotoxicity  
Figure 7: The effect of hydrogels on the activity of superoxide dismutase. ***\(p<0.0001\), ***\(p\leq 0.0009\), ***\(p=0.0017\), *\(p=0.0476\) versus the control. between the tested hydrogels. This cytotoxicity was concentration-dependent. In the case of the AB test, a positive effect of H-CON and H-CON-TER hydrogels was noted, for which an increase in the viability of fibroblasts was achieved to 126.0% and 123.0%, respectively. In the case of HaCaT cells, the increase in viability reached 136.0% for H-CBD and 135.0% for H-CBD-TER. Only in the two lowest concentrations (0.01 and 0.1%) did H-TER hydrogel not induce cytotoxicity on BJ and HaCaT cells. In contrast, with the concentration increasing, their viability decreased to 69.0% and 78.0%, respectively (Figures 8 and 9). Similar results were obtained in the NRU test. This test showed that with an increase in the concentration of the H-CBD hydrogel, the viability of both cell lines increases to about 130.0% when using a 5.0% hydrogel concentration. For the H-CBD-TER hydrogel, the most positive effect was observed for the concentration of 1.0%, for which an increase in viability was observed by 126.0% for BJ cells and 129.0% for HaCaT. The H-TER hydrogel showed a dose-dependent cytotoxic effect on both cell types, limiting their viability to 74.0% (BJ cells) and 63.0% (HaCaT cells) (Figures 10 and 11). Assessing the impact of DDSs to be applied on the skin surface is critical in assessing their safety. The research results described above indicate that the hydrogels H-CBD and H-CBD-TER do not induce cytotoxic effects on skin cells in vitro, which may indicate their potential use in the treatment of skin diseases. [PERSON] et al. pointed out the crucial role of CBD in the differentiation of keratinocytes, skin development, and differentiation of epidermal cells. They showed that CBD can induce keratinocyte proliferation, expression of several NRF2 target genes, nuclear export and degradation of BACH1, expression of heme oxygenase 1 (HMOX1) independently of NRF2, and increases in keratin 16 and 17 levels, which significantly affects keratinocyte proliferation and wound repair [47]. [PERSON] et al. noted that the positive effect of CBD on skin cells is also associated with the inhibition of the release of inflammatory mediators by impairment of the kappa B (NF-\(\kappa\)B) nuclear pathway, which was observed in both keratinocytes and fibroblasts. This compound also influences the release of interleukin-8, vascular endothelial growth factor (VEGF), and metalloproteinase 9 (MMP-9) [48]. Studies by [PERSON] et al. also indicate that CBD effectively protects keratinocytes against the adverse effects of UVB radiation, which is mainly related to the change in the expression of proteins involved in regulating the translation and proliferation of these cells [48]. [PERSON] et al. demonstrated that the protective effect of CBD on UV-irradiated keratinocytes might be related to the increased activity of antioxidant enzymes such as superoxide dismutase and thioredoxin reductase. Moreover, this compound prevents lipid peroxidation by lowering the level of 4-HNE and 15d-PGJ2 and influences the interaction of NRF2-NF\(\kappa\)B transcription factors [49]. The cytoprotective effect was also proven in the studies of [PERSON] et al., who observed a decrease in the expression level of CASP1 and IL1B mRNA and decreased IL-1B after treatment with H2O2 keratinocytes. Moreover, the phytocannabinoid reduced pyroptosis induced by H2O2 and apoptosis [50].