Real-time electrocatalytic sensing of cellular respiration

Abstract

In the present work we develop a real-time electrochemical mediator assay to enable the assessment of cell numbers and chemical toxicity. This allowed us to monitor metabolism down to a single cell in a low cost easy to use rapid assay which is not possible with current technology. The developed assay was based on the determination of oxygen. This was made possible via the use of electrochemical mediator ferrocene carboxylic acid (FcA). The FcA showed distinctive catalytic properties in interacting with reactive oxygen species generated from oxygen when compared to ferrocene methanol (FcMeOH). A deeper insight into the chemistry controlling this behaviour is provided. The behaviour is then taken advantage of to develop a cellular aerobic respiration assay. We describe the properties of the FcA system to detect, in real-time, the oxygen consumption of Escherichia coli DH5-α (E. coli). We demonstrated that the FcA-based oxygen assay is highly sensitive, and using a population of cells, oxygen consumption rates could be calculated down to a single cell level. More importantly, the results can be accomplished in minutes, considerably outperforming current commercially available biooxygen demand assays. The developed assay is expected to have a significant impact in diverse fields and industries, ranging from environmental toxicology through to pharmaceutical and agrochemical industries.

Hydrodynamic chronoamperometry for probing kinetics of anaerobic microbial metabolism – case study of Faecalibacterium prausnitzii

“…Some previous studies proposed their redox-based methods for rapid estimation of active cell concentrations in pure culture suspensions. However, they showed no or quite limited linear response with bacterial concentration 19 38 /amount 39 (one order of magnitude or less) likely because measurements were done by non-dynamic CV without convection 19 38 or with bacteria immobilized on the electrode 39 . The RDE method as presented here allows for higher sensitivity and avoids substrate and/or mediator diffusion issues 18 .…”

“…Other techniques roughly consist of intermittently (often only two times) measuring the redox state of the mediator by voltammetry or chronoamperometry performed under stagnant conditions with (micro)electrodes after the microorganisms have been incubated for a specific time with its substrate(s) and redox mediator(s) 3 4 5 7 8 12 19 20 . The monitoring is not continuous in this case and cannot, among others, record fast cellular events induced by an external stimulus .…”

Oxidative stress in severe pulmonary trauma in critical ill patients. Antioxidant therapy in patients with multiple trauma — a review

“…Such mechanisms that can generate free radicals inside the body are represented by: the activation of neutrophils, the electron transport chain at the mitochondrial level, arachidonic acid metabolism, oxide-reduction of xanthine [28] or nitric oxide synthesis [27,[29][30][31]. The respiratory chain [32][33][34] has a key role at the cellular level, being responsible for the conversion of oxygen in water molecules. At the neutrophils' level, the major source of oxygen is the enzymatic complex NAD(P) H oxidase.…”

Acute biotoxicity assessment of heavy metals in sewage sludge based on the glucose consumption ofEscherichia coli

“…A higher PGM signal was detected with the increase of Cu 2+ and Zn 2+ concentration [40]. Under the consistent parameter optimization of bioassay in terms of E. coli and B. subtilis concentration, culture temperature and OD 600 values [41,42], E. coli were more sensitive and suitable for heavy metal biotoxicity assessment in the following studies.…”