Immuno‐affinity Amperometric Detection of Bacterial Infections

Abstract

A combination of an immuno-affinity enrichment strategy and sensitive amperometric read-out was implemented in a point-of-care platform intended for bacterial infection analysis. Bacterial cells, selectively captured and enriched from complex matrices through immuno-affinity, were detected by amperometric monitoring of the redox state of metabolic activity indicators, providing species identification and viable-cell quantification. The method was successfully employed for the diagnosis of bacterial infections including antimicrobial susceptibility testing with only several hours of total working time.

Highly Loaded Mildly Edge‐Oxidized Graphene Nanosheet Dispersions for Large‐Scale Inkjet Printing of Electrochemical Sensors

“…The classical procedure of living bacterial cell detection with redox indicators is based on the metabolic consumption (cellular reduction) of the redox indicator (i. e., a compound that can be reduced by the uptake of an electron) by the respiratory electron transport chain of living bacterial cells . The consumption of the redox indicator is time‐dependent and can be used for the detection and quantification of living bacterial cells in a liquid sample . This concept has been known and is well‐adopted in colorimetric bacteria assays, but recently also found application in electrochemical sensing as many of the known metabolic activity indicators are electro‐active .…”

“…Voltammetric reduction signals for the oxidized redox indicator decay in the presence of living bacterial cells. In our previous work, bacteria were captured by antibody‐coated magnetic beads and concentrated on a specialized carbon nanotube electrode with a magnet below and a well plate on top to keep the reaction solution near the electrode . The use of antibodies facilitates the detection of bacteria from species level, but the immune‐affinity capture process is labor‐intensive and time consuming.…”

“…The tetrazolium salts showed reduction peaks of different shapes and at different potentials depending on their molecular structure. Resazurin showed two reduction peaks (−0.2 V and −0.36 V), from which the first corresponded to the irreversible reduction of RS to resorufin and the second to the reversible reduction to dihydroresorufin (SI‐9) . Afterwards, the electrochemical response of the redox indicator solutions without bacteria and with bacteria (∼8.3×10 8 E. coli cells/mL with 30 min incubation) were investigated.…”

“…Real matrices might cause interferences and require further sample preparation, such as centrifugation, supernatant disposal, washing and re‐dispersing in LB. Specificity can be achieved by capturing and washing of the captured bacteria using immunoassay‐based approaches . In addition, electrochemical detection in complex matrices might require a protecting layer on the EOGN working electrode, for instance by a polyacrylamide‐based nano‐hydrogel layer as recently demonstrated for long term measurements of bacterial metabolites in artificial wound fluids .…”

“…CV was applied for the electrochemical characterization of the printed sensors and redox indicators. DPV was applied as an exemplary pulsed voltammetric technique for bacteria detection following our previous works . Experimental parameters for the CVs and DPVs are given in the according sections and figure captions ( vide infra ).…”