Scanning electrochemical and atomic force microscopy as a tools for the investigation of yeasts Saccaromyces serevisiae

Abstract

Saccharomyces cerevisiae (S. cerevisiae) is a simple eukaryotic cell, which is serving as a model system for eukaryotes, including humans, for the study of fundamental cellular processes [1]. Yeast cells can be used as a recognition unit in biosensors [1,2]. The possibility to investigate a biosensors’ surface by scanning electrochemical microscopy (SECM) and demonstration of the different properties of biosensors is provided by the use of various mediators to image cell using SECM [1,2]. SECM has an advantage compared to other types of scanning microscopes, because the electrode is not in contact with the cell surface and the sample is not directly violated. SECM is also very convenient to investigate cells in their favored medium. Atomic force microscopy is a valuable and useful tool for the imaging and investigation of living cells in their natural environment at high resolution [3]. AFM-based techniques can be applied in order to get additional information about the physical properties of biological samples, such as Young’s modulus and adhesion forces [3]. Structural changes induced in the cell membrane, the cytoskeleton, and the cytosol, changes in the cell shape and size, and changes in cell deformability show cell’s diseases. The most effective among others mediators for SECM cell imaging was found 9,10-phenetrenechinone (PQ), which is able to act as second redox mediator in the charge transfer chain of yeast cells, when ferricyanide is used as first redox mediator. The UME current, measured with PQ as a second redox mediator, was more than 3 times higher than others here evaluated redox mediators. Therefore, the toxicity of PQ is also 3 times higher than others redox mediators. Yeast cells, affected by PQ, were measured by AFM in contact mode. The results show, that after exposure with 0.05 mM PQ, cells morphology was not changed extremely, but it can be seen increase in cells surface roughness. After second exposure, cells surface looks more ‘flatten’, and it can be explained as decrease in cells viability. Thus, both techniques are suitable for investigation of cells viability and can be applied for toxicity investigations, where yeasts’ serve as a model system.