## 3 Results and Discussion
### Selection of Material and Technology  
After analysing the defined areas, criteria (Figure 1), and requirements (Table 2), it had transpired that the adapter meets the conditions for its production with the use of additive manufacturing. Therefore, the material and technology selection stage began. Regarding the economic and environmental criteria, the current availability and price of the materials were analysed. The choice of material that was used to produce the adapter was largely dependent on the availability of 3D printing devices in the laboratory. On this basis, the following technologies and materials were found to be available:  
* FDM-poly (acrylonitrile-co-butadiene-co-styrene) ABS;
* SLS-polyamide PA12. The results of biological tests carried out for the selected materials in the subsequent stages of the subprocess are presented below. In the FDM method, the ABS material was used in the form of a wire under the trade name ABS-M30 manufactured by Stratasys. In the SLS method, the samples were made of PA12 powder, available under the trade name PA2200 manufactured by EOS [15]. The materials were applied as delivered, with no pretreatment. In Figure 4, the results of the cytotoxicity tests of the materials are shown. Samples with a cytotoxicity below 30% are considered noncytotoxic, according to the standard. The \"minus\" sign next to the numerical value means that the extract from the incubation of the samples in the culture medium stimulated the test cells to grow beyond the cell growth level in the control system (untreated extract). The chart below shows that both the ABS material processed in the FDM and the PA12 material processed in the SLS are not cytotoxic for the tested cell lines. Of note, the PA12 material is characterised by a much lower level of cytotoxicity (\(-11.5\%\)) for Keratinocyte HaCaT compared to the ABS material (\(-1.1\%\)). Regarding the remaining cell lines, the PA12 material is also characterised by a lower level of cytotoxicity compared to the ABS material, but these differences are not very significant. For Fibroblast L929, the values are \(-14.5\%\) for PA12 and \(-9.5\%\) for ABS. For epithelial lung cells A459, which have the highest importance in this application, these values are \(-13\%\) for PA12 and \(-11.5\%\) for ABS, respectively. The assessment of the surface colonisation capacity by the microorganisms/potential antimicrobial activity in the Tryptic soya broth (system I) and in the artificial saliva (system II) are presented in Figure 5a,b, respectively. The figure shows the % of the number of live cells on the surface of the test samples compared to the number of cells grown on the control surfaces in the test system. Figure 4: The determination of the cytotoxicity level of the samples tested against HaCaT, L929, and A549 cell lines. The ABS for all of the analysed microbial strains shows low potential antimicrobial activity, both in the Tryptic soya broth (TSB) microbial medium and in artificial saliva (AS), as evidenced by the high percentage of the number of live cells on the surface of the tested samples compared to the number of cells grown on the control surfaces in research systems. For _S. aureus_, _P. aeruginosa_, and _C. difficile_, it was 98.4%, 93.1%, 91.5% in the Tryptic soya broth (TSB) microbial medium, and 98.5%, 87.2%, 87.4%, respectively in artificial saliva. On the other hand, the PA12 material was characterised by a much higher potential antimicrobial activity compared to ABS. The survival of the analysed strains of _S. aureus_, _P. aeruginosa_, and _C. difficile_ was found to be at the level of 98.5%, 87.2%, 87.4% in the microbiological medium of Tryptic soya broth, and 54.4%, 88%, 61.7%, respectively in artificial saliva. The above studies have shown that the selected materials are characterised by low cytotoxicity, which is particularly important when the manufactured elements come into direct contact with humans. In this case, it cannot be concluded that the selected materials are antibacterial.