Micro- and Nanoelectrodes: Fabrication, Characterization and Application. the Detection of Silver and ROS/Rns in Biological Buffer

Abstract

The electrochemical determination of low concentrations of silver, and the short-lived highly reactive oxygen and nitrogen species (ROS/RNS), requires reliable, reproducible measurements with sensitive analytical methods. In this work, gold, platinum and platinum black micro and nanoelectrodes were fabricated. Characterisation revealed flat disk-shaped working areas of 20 - 25 µm (micro) and 1 - 10 nm (nano) in diameter, derived from steady-state limiting currents and validated using FE-SEM.[1] Reported studies on silver detection have been carried out under a myriad of conditions but, to date, electrochemical determination of silver in biological buffers and media has not been successful.[2] Ultra-low concentrations of silver (1 nM – 80 nM) were determined, by anodic stripping voltammetry (ASV) with Ag/AgBr as a reference electrode, using micro- and nanoelectrodes of platinum and gold in chloride-free phosphate buffer (PB, pH 7.4). Laser pulled electrodes exhibit highly reproducible stripping voltammetry data for the determination of silver and returned linear calibration curves. A low detection limit of 1.3 pM in this medium provides the ability to explore silver and silver-based bioinorganic drug uptake by tumour and microbial cells. [3]This study also includes the fabrication of Pt/Pt-black nanoelectrodes for the detection of ROS/RNS in chloride-free PB (pH 7.4). These data should help with the identification and quantitation of cellular ROS/RNS release. In particular, monitoring oxidative stress, as a cellular response on exposure to bioinorganic drugs, should help to elucidate the interaction pathway of bioinorganic anti-cancer drugs. We envisage that electrochemical speciation studies will help to elucidate the mechanism of action and cellular uptake of bioinorganic silver-based anti-microbial and anti-cancer drugs in cell sustaining media for in vitro and, potentially, in vivo single cell analysis. [1] Percival, S. J. et al., RSC Adv. 2014, 4 (21), 10491. [2] Radulescu, M. C. et al., Sensors 2010, 10 (12), 11340. [3] Prabhakar Sidambaram. et al., J. Electrochem. Soc. 2019, 166, 6, B532.