A Minimally Invasive Microsensor Specially Designed for Simultaneous Dissolved Oxygen and pH Biofilm Profiling

Abstract

A novel sensing device for simultaneous dissolved oxygen (DO) and pH monitoring specially designed for biofilm profiling is presented in this work. This device enabled the recording of instantaneous DO and pH dynamic profiles within biofilms, improving the tools available for the study and the characterization of biological systems. The microsensor consisted of two parallel arrays of microelectrodes. Microelectrodes used for DO sensing were bare gold electrodes, while microelectrodes used for pH sensing were platinum-based electrodes modified using electrodeposited iridium oxide. The device was fabricated with a polyimide (Kapton®) film of 127 µm as a substrate for minimizing the damage caused on the biofilm structure during its insertion. The electrodes were covered with a Nafion® layer to increase sensor stability and repeatability and to avoid electrode surface fouling. DO microelectrodes showed a linear response in the range 0–8 mg L−1, a detection limit of 0.05 mg L−1, and a sensitivity of 2.06 nA L mg−1. pH electrodes showed a linear super-Nernstian response (74.2 ± 0.7 mV/pH unit) in a wide pH range (pH 4−9). The multi-analyte sensor array was validated in a flat plate bioreactor where simultaneous and instantaneous pH and DO profiles within a sulfide oxidizing biofilm were recorded. The electrodes spatial resolution, the monitoring sensitivity, and the minimally invasive features exhibited by the proposed microsensor improved biofilm monitoring performance, enabling the quantification of mass transfer resistances and the assessment of biological activity.

Quercetin-Crosslinked Chitosan Films for Controlled Release of Antimicrobial Drugs

“…Also, chitosan/quercetin composites have been demonstrated to possess a pH-dependent release kinetic ( Mu et al, 2019 ), confirming the hereby presented results. Furthermore, releasing under acidification is interesting against bacterial biofilms since the biofilm growth of some bacteria such as Staphylococci causes a decrease in pH ( Liermann et al, 2000 ; Guimer et al, 2019 ; Schultze et al, 2020 ). The decrease in pH values could therefore trigger the release of TMP from the chitosan-quercetin films, acting as a response against bacterial infection.…”

A Review of Methods to Determine Viability, Vitality, and Metabolic Rates in Microbiology

“…Alternatively, for now, 3D printing and rapid prototyping methods also allow rapid development of microfluidic devices that can incorporate such new sensors. Finally, it must be noted that such chips are very close to becoming reality, as several authors have already presented multiple parameters using separate microprobes or microfluidic chips simultaneously measuring pH, OD, and dissolved oxygen, for example ( Wong et al, 2015 ; Guimer et al, 2019 ). Still, as this is a rapidly evolving field, many new sensor types might appear in the next years.…”

Development of Flexible Ion-Selective Electrodes for Saliva Sodium Detection

“…We used the same structure in our previous study on the flexible circuit [ 5 ]. However, considering that the flexible RE often contributes to an unstable signal in a potentiometric detection setting [ 30 ], the device’s sensing reliability was further improved by making a rigid film on top of the Si wafer. The rigid RE electrode was prepared by an e-beam evaporation of Ag, vacuum annealing, surface chlorination, and membrane coatings (details in Materials and Methods).…”