# Perspective of Using Vertically Oriented Graphene as an Electrochemical Biosensing Platform
## 4 Conclusions  
By correlating all of the characterization methods presented in this work, we can comprehensively understand vertical graphene's structural, morphological, chemical, and electrochemical properties. The results obtained from Raman spectroscopy, SEM analysis, TEM analysis, AFM, FTIR, and EIS collectively demonstrate the suitability of vertical graphene for use in electrochemical sensors, highlighting its potential for enhanced sensing performance, high surface area, efficient charge transfer, biocompatibility, and stability. The HT 29 cells, compared to SW 403, have lower electrical charge transfer resistance and higher electrical permittivity and conductivity. Also, HT29 tumor cells have a highly folded membrane surface due to microvilli and, therefore, have a much larger cell surface than cells in the SW403 line. HT29 has a higher membrane capacity and a lower capacitive reactance. Its higher membrane capacitance stores more electrical charges, leading to a lower charge transfer resistance and higher conductivity. Cells exhibit a dielectric signature that reflects their response to electromagnetic fields at various frequencies. This response is influenced by interactions between the electromagnetic fields and the molecules within the cellular membrane. The presence of VG on gold electrodes enhances the interface between the electrodes and the biomolecules, resulting in increased biodetection surface and electrode conductivity. VG, a carbon nanomaterial, possesses higher electron mobility, making it a suitable choice for this modification. The electrochemical analysis demonstrated the effectiveness of the VG-modified electrochemical sensor in detecting tumoral cells on the electrode surface at concentrations of \(10^{4}\) and \(10^{6}\) cells/mL. The EIS results showed that the HT 29 cell line had a larger cell membrane surface and lower capacitive reactance than the SW 403 cell line. The HT 29 cells had a higher conductivity and lower resistance to charge transfer due to their larger capacity to store electrical charges. This was attributed to many lipidic bonds at the microvilli, particularly cholesterol-ol-glycosphingolipids. Moreover, the SW 403 cells adhered and formed large cellular conglomerates, while the HT 29 cells had a higher conductive surface and experienced superior dielectric losses through conduction, as confirmed by the EIS measurements. The observed decrease in Rct with an increase in tumor cell concentration is a complex outcome of these interacting factors. It is not solely due to electron obstruction but because of the dynamic interplay between the tumor cells and the electrochemical processes at the electrode surface. This phenomenon provides valuable insights into the behavior of tumor cells in our experimental system. Conceptualization and writing--original draft, E.A. and B.A. ; review & editing, E.A., B.A., I.D. and A.A.; investigation, E.A. and B.A. ; funding acquisition, E.A., I.D. and A.A. All authors have read and agreed to the published version of the manuscript. This research was funded by the European Social Fund from the Sectoral Operational Programme Human Capital 2014-2020, Contract No. 13530/16.06.2022--SMIS Code: 153734. We kindly acknowledge [PERSON] from the National Institute for Research and Development in Microtechnologies--IMT Bucharest for the Raman spectrum of VG, [PERSON] from the National Institute for Research and Development in Microtechnologies--IMT Bucharest for the SEM image of VG, [PERSON] from the National Institute of Material Physics--Romania for the TEM image of VG, [PERSON] from Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering for the AFM topography of VG, and [PERSON] from the National Institute for Research and Development in Microtechnologies--IMT Bucharest for the FTIR spectrum of VG.