Label-Free Optical Imaging of the Electron Transfer in Single Live Microbial Cells

Abstract

Measurement of electron transfer at the single-particle or -cell level is crucial to the in situ study of basic chemical and biological processes. However, it remains challenging to directly probe the microbial extracellular electron transfer process due to the weakness of signals and the lack of techniques. Here, we present a label-free and noninvasive imaging method that is able to measure the electron transfer in microbial cells. We measured the extracellular electron transfer processes by imaging the redox reaction of c-type outer membrane cytochromes in microbial cells using a plasmonic imaging technique, and obtained the electrochemical activity parameters (formal potential and number of electrons transferred) of multiple individual microbial cells, allowing for unveiling ample heterogeneities in electron transfer at the single-cell level. We anticipate that this method will contribute to the study of electron transfer in various biological and chemical processes.

Hydrogel‐Assisted Electrokinetics for High‐Resolution and Non‐invasive Flow Monitoring in Microfluidic Chips†

“…Microfluidic chips that integrate sampling, mixing, diluting and separating processes on a single platform offer a powerful tool for tissue engineering, [1][2] health monitoring, [3] drug development [4][5] and energy conversion. [6][7] The flow velocity of fluids is a critical parameter for quantitative analysis of molecules, precise control of nutrient perfusion, drug delivery and energy efficiency optimization. [8][9][10] To measure the flow velocity, various flow sensors have been proposed and integrated with microfluidic chips, ranging from thermal flowmeter to piezoelectric and piezoresistive sensors.…”

Surface Plasmon Resonance Biosensors: A Review of Molecular Imaging with High Spatial Resolution

“…Owing to the high numerical aperture of the objective, SPRM can reach a diffraction-limited spatial resolution of ~300 nm perpendicular to the propagation direction of surface plasmon waves, which has been widely used in the imaging of single nanoparticles [43][44][45][46] and single cells [23], subcellular organelles [47], virions [48,49], nanoparticles [50,51], nanobubbles and exosomes [52]. In addition, SPRM can also utilize the exponentially decaying properties of the electric fields of the surface plasmon waves to track the sample movements at the axial direction for quantitatively determining the interactions of nanoparticles or biological entities with the surface, thus providing a powerful tool to understand particle absorption mechanisms [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70]. In addition, owing to the fact that the resonance condition of SPR depends on the refractive index near the sensor surface, SPRM can also be combined with electrochemical workstations for studying the spatial distributions of electrochemical reaction kinetics [71][72][73].…”

Operando Spectroscopic Elucidation of the Bubble Sunshade Effect in Inorganic–Biological Hybrids for Photosynthetic Hydrogen Production

“…Studies of the photosynthetic process at the single-cell level can offer mechanistic and quantitative guidance for improving energy conversion efficiencies . Microscopic tools, including fluorescent imaging, − spectral methodologies, , and plasmonic microscopies, , are crucial for monitoring the dynamics of individual cells. Nevertheless, realizing the observation of photosynthetic kinetics at the single-cell level with abundant dynamic and spectroscopic information remains elusive.…”