Detection of Saccharomyces cerevisiae immobilized on self-assembled monolayer (SAM) of alkanethiolate using electrochemical impedance spectroscopy

The preparation of chemically functionalized self-assembled monolayer (SAM) surfaces is of great interest for applications in the immobilization of various bioactive species such as enzymes, DNA, whole cells, etc. In this paper, an electrochemical impedance biosensor for the rapid detection of Saccharomyces cerevisiae (yeast cells) was developed by immobilizing yeast cells on a gold surface modified with an alkanethiolate SAM. The patterns formed on the gold electrode surface after the assembly of 3-mercaptopropionic acid (MPA) monolayer and the immobilization of yeast cells were clearly observed from atomic force microscopy (AFM) and optical microscope, respectively. The electrochemical impedance spectroscopy (EIS) measurements were based on the charge-transfer kinetics of [Fe(CN)6]3−/4− redox couple. The SAM assembly and the subsequent immobilization of yeast cells on the gold electrodes greatly increased the electron-transfer resistance (Ret) of the redox couple and decreased the double layer capacitance (Cdl). A linear relationship between the Ret and logarithmic value of yeast concentrations was found in the range between 102 and 108 cfu mL−1.