Profiling of oxygen in biofilms using individually addressable disk microelectrodes on a microfabricated needle

Abstract

A novel microelectrode array sensor was fabricated using MEMS technology on a needle, and then applied to real-time measurement of dissolved oxygen (DO) inside biofilms. The sensor consists of eleven gold disk microelectrodes and a rectangular auxiliary electrode along them and an external & internal reference electrode. Three kinds of sensors were designed and their responses were characterized and evaluated under various environmental conditions. The arrays exhibit a linear response to DO in the 0 -8 mg L -1 concentration range in water, high sensitivity, repeatability, and low limits of detection (< 0.11 mg L -1 ) and quantification (0.38 mg L -1 ). The sensors were then validated against a commercial Clark-type microelectrode and applied to profiling of DO in a heterotrophic biofilm cultivated in a flat-plate bioreactor. It is shown that the sensor array can provide a multipoint, simultaneous snapshot profile of DO inside a biofilm with high spatial resolution due to its micrometric dimensions. We conclude that this new sensor array represents a powerful tool for sensing of DO biofilms and in numerous bioprocesses.

Simultaneous monitoring of Staphylococcus aureus growth in a multi-parametric microfluidic platform using microscopy and impedance spectroscopy

“…The punctual electrodes allow to make electrochemical measurements of DO, K +, Na + and pH. The amperometric measurement of DO is achieved using a working electrode (WE), a reference electrode (RE) and a counter electrode (CE) [24]. The measurement of Na+ and K + ions is performed with a potentiometric ion-selective technique using the WE for each ion measurement and the RE [27].…”

“…1D) described elsewhere [24,26] for measuring different biofilm parameters of interest. The punctual electrodes allow to make electrochemical measurements of DO, K +, Na + and pH.…”

“…The system is designed to be used in multiple environments and to allow simultaneous and continuous monitoring of biofilm proliferation under shear stress using optical microscopy and multiple read-outs. The chip used in this study contains two IDuEs (rectangular and circular) and punctual electrodes to measure dissolved oxygen (DO) [24], K+, Na+ and pH. Two-and four-electrode configuration impedance measurements can be performed indistinctly on the same IDuE.…”

Miniaturized multiparametric flexible platform for the simultaneous monitoring of ionic: Application in real urine

“…Oxygen concentrations were changed by a nitrogen-air distributor. DO sensor calibration and the characterization [35] was done using the 8-channel potentiostat (1030A Electrochemical Analyzer, from CH-Instruments). The pH sensor calibration was done in different pH solutions and a commercial pH-meter was used for the correlation of the obtained potentials (GLP22, from Crison).…”

“…DO in urine is not a relevant physiological parameter and has to be measured under very stringent conditions that cannot be met with the use of stored samples. However, oxygen control is essential for cell cultures systems since is vital in the energy metabolism of cells and, moreover it is an important regulatory parameter, influencing cell differentiation and tissue zonation [34,35]. We are currently using this platform for DO measurements successfully, in projects involving monitoring of metabolic activity in human cell cultures.…”