Exploring the Living Cell: Applications and Advances of Scanning Electrochemical Microscopy.

A living cell is a complex network of molecular, biochemical and physiological processes. Cellular activities, such as ion transport, metabolic processes, and cell-cell interactions can be determined electrochemically by detecting the electrons or ions exchanged in these processes. Electrochemical methods often are noninvasive, and they can enable the real-time monitoring of cellular processes. Scanning electrochemical microscopy (SECM) is an advanced scanning probe electroanalysis technique that can map the surface topography and local reactivity of a substrate with high precision at the micro- or nanoscale. By measuring electrochemical signals, such as redox reactions, ion fluxes, and pH changes, SECM can provide valuable insights into cellular activity. As a result of its compatibility with liquid medium measurements and its nondestructive nature, SECM has gained popularity in living cell research. This review aims to furnish an overview of SECM, elucidating its principles, applications, and its potential to contribute significantly to advancements in cell biology, electroporation, and biosensors. As a multidisciplinary tool, SECM is distinguished by its ability to unravel the intricacies of living cells and offers promising avenues for breakthroughs in our understanding of cellular complexity.

Scanning electrochemical microscopy based irreversible destruction of living cells.

In this research, scanning electrochemical microscopy combined with electrochemical impedance spectroscopy has been applied to irreversible electroporation of active yeast cells by causing cell death. This finding is important for the development of irreversible electroporation technique, which could be suitable for the curing of cancerous tissues, because during this research cell death has been achieved using relatively low ultramicro-electrode (UME) voltage, precisely of 2.0 V vs Ag/AgCl,Cl-sat. It was determined that the irreversibly electroporated area of immobilized yeast cells was located directly below the UME and was of approximately 20 times larger width than the diameter of the UME, leaving undamaged cells out of this area. The ability of SECM to move the UME with high accuracy in x, y, and z directions and the ability to use electrodes of various diameters as well as the fact that the diameter of the electroporated area depends on the diameter of the UME and on the distance between the UME and the surface, what offers the possibility to establish targeted electroporation systems for selective treatment of tissues.

Scanning electrochemical microscope as a tool for the electroporation of living yeast cells.

In this study, a scanning electrochemical microscope (SECM) was for the first time adapted to perform the electroporation process of living yeast cells. We have demonstrated that relatively low voltage pulses of 1-2 V vs. Ag/AglCl,Cl-sat applied to gold-based ultramicroelectrode (Au-UME) are performing reversible electroporation of yeast cells immobilized on fluorine-doped tin oxide (FTO)/glass surface. SECM and electrochemical impedance spectroscopy (EIS) were used for the determination of quantitative electrochemical characteristics before and after the electroporation. The electrochemical impedance spectroscopy (EIS) illustrated significant electrochemical changes of electroporated yeast cells, while SECM feedback mode surface vertical scan current-distance curves showed that the diameter of the area affected by the electrical pulse is about 25 times larger than the diameter of the Au-UME used for the electroporation process. The results presented in this research open up a possibility to develop a targeted electroporation system which will affect only the selected area of tissue or some other cell-covered surface. Such model is promising for the selective treatment of selected cells in tissues and/or other sensitive biological systems while selecting the location and size of electroporated areas.

Electroporation of a hybrid bilayer membrane by scanning electrochemical microscope.

A novel method, suitable for targeted electroporation of hybrid bilayer membranes (hBLMs) by scanning electrochemical microscope (SECM) is introduced by this work. A redox-probe-free system was applied for (i) SECM-based electroporation of a hBLM and for (ii) SECM-based visualization of pores formed by SECM-based electroporation in the hBLM. The hBLM was formed on a glass substrate modified by fluorine-doped tin oxide, and the structure (glass/FTO/hBLM) was used for further investigations. A specific 'constant-current region' at 1-30 µm distances between the UME and the hBLM surface was observed in the approach curves, which were registered while a Pt-based ultramicroelectrode (UME) was approaching the glass/FTO/hBLM surface. This 'constant-current region' was used as the characteristic feature for characterisation of the hBLM, and by assessment of the approach curves it was possible to distinguish whether an area of the hBLM was electroporated. SECM-based electroporation of the hBLM was performed by using increased potential difference between the reference electrode and the UME. Depending on the duration of the applied potential-pulse and on the distance between the UME and the hBLM surface, irreversible or reversible electroporation of the hBLM was achieved. The data shows that SECM can be successfully applied for both electroporation and characterisation of the hBLM.

Silane-based self-assembled monolayer deposited on fluorine doped tin oxide as model system for pharmaceutical and biomedical analysis.

Recently, self-assembled monolayers (SAMs) are gaining a lot of interest due to their simplicity of preparation and wide applicability in the development of model systems used in pharmaceutical and biomedical analysis. The most efficient methods used for the investigation of SAM-based structures usually include cyclic voltammetry and electrochemical impedance spectroscopy. Scanning electrochemical microscopy (SECM) could be also used as an alternative method for SAM investigations, because this method enables to map modified surface. In this work, the surface of fluorine doped tin oxide (FTO) was modified with octadeciltrichlorosilane (OTS) based SAM and investigated using SECM. Measurements, which were carried out by SECM, lead to conclusion that highly heterogeneous and distributed monolayer has been formed on FTO surface.