Analysis of Electrochemically Elusive Trace Metals with Carbon Fiber Microelectrodes

A facile approach to create sensitive and selective Cu(ii) sensors on carbon fiber microelectrodes

A facile platform derived from deposition of ethynyl linkers on carbon fiber microelectrodes has been developed for sensitive and selective sensing of Cu(ii). This study is the first to demonstrate the successful anodic deposition of ethynyl linkers, specifically 1,4-diethynylbenzene, onto carbon fiber microelectrodes. Multi-scan deposition of DEB on these microelectrodes resulted in an increased sensitivity and selectivity towards Cu(ii) that persists amidst other divalent interferents and displays sustained performance over four days while stored at room temperature. This method can be extended to other ethynyl terminal moieties, thereby creating a versatile chemical platform that will enable improved sensitivity and selectivity for a new frontier of biomarker measurement.

Extended sawhorse waveform for stable zinc detection with fast-scan cyclic voltammetry

Zinc (Zn(II)) is a divalent cation involved in regulating intracellular signal transduction and gene expression through transcription factor activity, and can act as a metal neurotransmitter by modulating synaptic activity and neuronal plasticity. Previous research has demonstrated spatial heterogeneity of Zn(II) in the brain, has estimated extracellular concentrations of Zn(II) across various brain regions, and has measured rapid intracellular changes in Zn(II) concentration during glutamate flux. Despite this work, quantification of rapid extracellular Zn(II) release from neurons, on a millisecond time scale, in real time has remained difficult with existing technologies. Here, we have developed an electrochemical waveform, called the "extended sawhorse waveform (ESW)," for fast-scan cyclic voltammetry detection at carbon-fiber microelectrodes which enabled rapid and stable Zn(II) monitoring over time. This waveform was developed to overcome existing challenges in monitoring metallotransmitters stably over time electrochemically by introducing a brief cleaning step to facilitate rapid cleaning of the electrode surface in between scans. The ESW scans from 0.5 V down to -1.0 V, up to 1.45 V for 3 ms (cleaning step), and back to 0.5 V at a scan rate of 400 V/s. Repeated introductions of Zn(II) at the electrode using a traditional waveform cause plating which ultimately deteriorates the sensitivity over time; however, using the ESW, significant improvements in stability were observed. Overall, we provide a unique approach to monitor and quantitate rapid Zn(II) signaling in the brain at carbon electrodes which will impact our ability to advance fundamental knowledge of Zn(II) involvement in extracellular signaling pathways in the brain.