**5. Conclusions**

In this study, we present the proof-of-concept development of a complementary, non-invasive cell analysis method to assess the responses of 3D cultured cancer cell lines derived from various tissues following treatment with cytotoxic concentrations of the well-studied anticancer compound, 5-FU, using bioelectricalal evaluation. A key-feature of the cell-based bioelectrical sensor was the 3D printing of a PETG well, assembled with two gold-coated electrodes, perpendicularly wall-mounted at the bottom, allowing for impedance measurements. The evaluation of our cell bio-system configuration showed good efficacy towards different cell type determination with adequate sensitivity. In order to obtain higher levels of selectivity, and sensitivity based on very low cell populations (up to single-cell analysis), it is necessary to fabricate a different electrode configuration (e.g., screen-printed) which is suitable for single-cell impedance spectroscopy [70–72]. As a next step, we plan to conduct more detailed impedance spectral analyses by using a considerably wider continuous frequency range, rather than the discrete values that were used in the present approach, as well as to investigate the effect of different cell immobilization agents on the bioelectric profiling process.

**Author Contributions:** Conceptualization—G.K. and S.K.; Data curation—G.P. and S.M.; Formal analysis—G.P. and S.M.; Investigation—G.P. and S.M.; Methodology—G.K. and S.K.; Resources—S.M.; Validation—G.P.; Visualization—G.P.

**Funding:** This work is supported by the H2020-EU.1.3.3. program of the topic MSCA-RISE-2017 entitled "NanoFEED: Nanostructured carriers for improved cattle feed" (Grant agreemen<sup>t</sup> ID: 778098).

**Conflicts of Interest:** The authors declare no conflict of interest.
