Integration of ring nanoelectrodes into microwells for the bioelectrochemical analysis in sub-picolitre volumes

Abstract

In this work, we report the fabrication and the electrochemical characterization of recessed disk microelectrodes (DME) and ring nanoelectrodes (RNE) integrated in microwell arrays. Such configuration has all advantages of microelectrodes arrays but is more suitable for electrochemical measurement in sub-picolitre volumes (~ 0.3 pL). The technological process based on the reactive ion etching of a SiO2/Ti/Pt/Ti/SiO2 stack is optimized in order to integrate RNE arrays on transparent glass substrate. Multiphysic simulations and electrochemical characterizations are conducted in order to study and improve the amperometric behaviour of recessed ring nanoelectrodes according to their geometry. A good fit is shown between experimental, theoretical and simulation results, allowing full understanding of the electrochemical detection properties of RNE-based microwell arrays. Then, a "generationcollection mode" chronoamperometric approach is proposed to evaluate experimentally the collection ratio of RNE arrays and compare it with simulation results. Finally, first electrochemical characterizations in sub-picolitre volumes are conducted with anti-oxidant species. All these results demonstrate that recessed ring nanoelectrode arrays are fitted to the detection of bio-electrochemical species at the microscale and, consequently to single mitochondrion or single sub-cellular organelle analysis.

Toward the analysis of mitochondria isolated from leukemic cells with electrochemically instrumented microwell arrays

“…Previous works [6] reported the design by multiphysics simulation, the manufacturing process and the electrochemical characterization of the first generation of the ElecWell. The following text will treat of the manufacturing of the second generation that is currently occurring.…”

“…A passivation layer of 100 nm of silicon nitride is deposited by inductivelycoupled plasma enhanced chemical vapor deposition (ICPECVD) and the active surface of the planar electrodes are defined by lift-off. Finally, a critical step of reactive ion etching (RIE) is performed to etch the stack SiO2/Ti/Pt/Ti/SiO2 using mixture of gases as described previously [6]. This final RIE step results in the formation of the microwells but also in the definition of the RNE at mid-depth and the disc microelectrode (DME) made of ITO at the microwell bottom.…”

Microwell array based opto-electrochemical detections revealing co-adaptation of rheological properties and oxygen metabolism in budding yeast

“…The design and fabrication of the microwell array reported here is inspired from our previous works where we reported the first generation of OptoElecWell and discussed its design by multiphysics simulation, manufacturing process and characterization (Sékli Belaïdi et al, 2016;Vajrala et al, 2019b).…”

“…However, this approach is still been faced with challenges in dealing with the low throughput owing to the manual positioning of the electrode near the cell and UME spatial coverage over the cell, i.e., partial detection of targeted cellular events due to lateral diffusion phenomenon. To overcome these limitations, we have recently developed a microwell array integrated with recessed ring-type micro/nanoelectrodes (RME/RNE) (Sékli Belaïdi et al, 2016;Vajrala et al, 2019). A functional and intricate integration of these RNE-based devices within microwells allowed us to entrap individual mitochondria in a high-throughput manner, and followed their respiration under several metabolic activation and inhibition conditions.…”

Toward the Analysis of Mitochondria Isolated from Leukemic Cells with Electrochemically Instrumented Microwell Arrays

“…Previous works reported the design by multiphysics simulation, the manufacturing process and the electrochemical characterization of the first generation of the ElecWell [2].…”