Micro- and Nano-Scaled Microbial Electrochemical Biosensing

Electroanalytical techniques combined with electroactive microorganisms (EAMs) are promising for fabricating microbial electrochemical biosensors (MEBs). Particularly, by scaling down the electrode size to micron or even nanometer dimensions, the electrode size becomes commensurate with the size of microbial cells, thus facilitating electrochemical investigation of the interactions between electrode-associated microbes and target analytes, even at the single-cell level. It becomes effective to elucidate by acquiring refined and distinctive electrochemical signals. Thus, this review gives insights into the principles of MEB, with particular emphasis on innovative ways to overcome limitations of conventional microbial biosensors by micro/nano-electroanalytical methodologies. Initially, the working principles of MEB, including the electrophysiology of microorganisms and the underlying mechanism for electrochemical signal output, are discussed. Subsequently, fundamental principles of micro/nano-electroanalytical techniques across diverse microbial biosensing strategies, with an emphasis on the synergistic effects between micro/nano-technology and microbial biosensing, are shown. Finally, applications and challenges faced in the integration of micro/nano-electroanalytical techniques and microbial biosensing are illustrated. Therefore, by covering biological processes, electrode materials and structures, as well as fabrication strategies at the micro- and nano-scales, this review may provide a comprehensive and unique perspective on electroanalytical techniques for micro- and nano-scaled analysis of microorganisms.