On-chip electrocatalytic NO sensing using ruthenium oxide nanorods

Abstract

Online, on-chip measurement of nitric oxide (NO) in organ-on-chip devices is desired to study endothelial (dys) function under dynamic conditions. In this work, ruthenium oxide (RuOx) is explored as an amperometric NO sensor and its suitability for organ-on-chip applications. For testing purposes, diethylamine NONOate was used as chemical NO donor. The NONOate's NO generation and electrochemical oxidation of generated NO were confirmed by real-time electrochemical/mass-spectrometry. Using RuOx nanorods electrodes, we show that NO oxidation occurred at a lower onset potential (+675 mV vs. Ag/AgCl) than on bare Pt electrode (+800 mV vs. Ag/AgCl). Due to NO adsorption on the RuOx surface, NO oxidation also delivered a higher current density (33.5 nA.μM − 1 . cm -2 ) compared to bare Pt (19.6 nA.μM − 1 . cm -2 ), making RuOx nanorods a favourable electrode for NO sensing applications. The RuOx electrode's suitability for organ-on-chip applications was successfully tested by using the electrode to detect a few micromolar concentration of NO generated by endothelial cell culture. Overall, the RuOx nanorods proved to be suitable for organ-on-chip studies due to their high sensitivity and selectivity. Our chip-integrated electrode allows for online NO monitoring in biologically relevant in vitro experiments.

Microfluidic organ-on-chip system for multi-analyte monitoring of metabolites in 3D cell cultures

“…In recent years, it has been shown, that the monitoring of metabolic parameters and culture conditions by means of embedded sensors can provide many benefits in terms of information content and quality of drug screening experiments, as well as fundamental metabolic characteristics of tissues. 16 Sensors for many different parameters such as oxygen, [17][18][19][20][21][22][23][24][25][26][27] superoxide, 28 nitric oxide (NO), 29 pH, 20,25,27,[30][31][32] transepithelial electrical resistance (TEER), 33-36 lactate, 19,23,31,37 glucose 19,31,37 and other biochemically relevant substances were developed and used for examination of static and dynamic 2D and 3D in vitro models. Optical sensors measure variations in optical properties, e.g.…”

Integrated Electrochemical and Optical Biosensing in Organs‐on‐Chip

“…[72] RuOx nanorods-based electrodes were used in an amperometric sensor for highly-sensitive and selective online monitoring of nitric oxide in OoCs (Figure 3C). [73] They showed RuOx is 115 times more selective to NO than NaNO 2 and reported a limit of detection of 250 mM. Moya et al presented a bioreactor platform for liver-on-chip comprising an upper microfluidic chamber and a static bottom chamber (Figure 3D).…”

Review of the Design of Ruthenium-Based Nanomaterials and Their Sensing Applications in Electrochemistry

“…106−110 For example, porous RuO 2 was used to catalyze Glu, 106,107 pH measurement, 108 H 2 O 2 , 109 and NO sensing. 110 RuO 2 is useful because of its great sensitivity, good catalytic performance, excellent thermal stability, and good chemical resistance. For instance, RuO 2 is a stable oxide and a focus of research interests in the development of pH sensors.…”

“…Because of the nanometer sizes, electronic structures, and topological defects present on the porous carbon surfaces, they have great capacity to promote electron transfer in a reaction when used as electrodes. Furthermore, porous carbon-coated RuO 2 NPs with a large surface area, exceptional adsorption capability, specific EC activity, and long stability are critical for sensor platform techniques. , Recently, Ru NPs-based electrocatalysts are frequently used as enzyme-free EC sensors. − For example, porous RuO 2 was used to catalyze Glu, , pH measurement, H 2 O 2 , and NO sensing . RuO 2 is useful because of its great sensitivity, good catalytic performance, excellent thermal stability, and good chemical resistance.…”