The Electrochemical Society hosted Prof. Jill Venton’s live webinar, “Novel Carbon Electrodes for Neurochemistry,” on May 26, 2021. Below are answers to questions posed after the presentation.
NOTE: Registration is required to view the webinar.
Dr. B. Jill Venton is Professor and Chair of the Department of Chemistry at the University of Virginia (UVA), U.S. She is also affiliated with the Neuroscience Graduate Program and UVA Brain Institute. Dr. Venton received her BS in Chemistry from the University of Delaware, U.S.; her PhD in Chemistry from The University of North Carolina at Chapel Hill, U.S.; and did postdoctoral research at the University of Michigan, U.S. Her career at UVA started in 2005 and she became Chair of the Department of Chemistry in 2019. The Venton Group’s research focuses on developing analytical chemistry tools for neuroscience research. The lab studies many neuroscience diseases, from Parkinson’s, to addiction, stroke, and aging.
Is it a normal practice to have widely different concentrations of analyte while comparing their CVs?
When we test neurochemicals, we try to test them near their physiological concentrations in the brain. The physiological concentration of dopamine is in the tens of nanomolar for basal levels and changes can be up to one micromolar. However, ascorbic acid (an antioxidant) and DOPAC (a metabolic breakdown product of dopamine) are present at much higher levels, tens to hundreds of micromolar. Thus, we test them at higher concentrations.
Did you check the surface charge of CNT and CNP? Wettability? If they have different charges, can it effect adsorption of dopamine?
Surface charge and wettability are important characteristics for carbon nanomaterials. We often use materials with high numbers of surface oxide groups, and many of the treatments we use for the carbon nanomaterials introduce oxide groups. These surface oxide groups will give the surface more wettability which will decrease the contact angle on the surface. We don’t often measure contact angle because our electrodes are round, but you can measure it on flat carbon. Materials with more wettability and surface charge do tend to be better for adsorption.
Are there any non-invasive techniques to measure electrochemistry?
The main non-invasive techniques are fMRI and PET scanning, which can be performed in humans as well as animals. The disadvantage of these is that they don’t track actual neurotransmitters but changes in oxygen or receptor activation. For research purposes, there are new fluorescent sensors based on G-protein coupled receptors that turn fluorescent when a molecule such as dopamine binds to them. For in vivo monitoring, you still need to implant a fiber optic, so it isn’t non-invasive. But it is an interesting competitor to electrochemistry and will be developed further in future years.
What is the carbon nanospike phase? Graphitic?
The carbon nanospikes are a form of graphene, one that ends in small tips, which is why they are called nanospikes.
Do you expect scan rate independence in nanoporous carbon electrode?
Yes—if the electrochemistry is governed by thin-layer electrochemistry, then we expect the responses will be scan rate independent because there is no appreciable diffusion. Thin layer electrochemical behavior occurs when there is trapping of the analyte on the time scale of the experiment, so the analyte is trapped in the nanopores and cannot escape while we make an electrochemical scan.
By monitoring the dopamine levels in the body, what problems can we control and resolve?
We know that dopamine is involved in many neurological diseases such as Parkinson disease and addiction, and is the main neurotransmitter involved in locomotion and reward. Thus, a better understanding of dopamine levels will allow a better understanding of how dopamine is dysfunctional in these diseases.
How does pH affect your results?
pH affects results because all of the electrochemical reactions involve H+ and thus potentials are right shifted in acid and left shifted in base. In addition, changes in pH can affect the surface functional groups, which changes the background charging currents.
Can you see thin layer effects in vivo?
We can see the thin layer effects in vivo, likely even more than in a beaker. That’s because in vivo a layer of protein also sticks to the electrode which will hinder diffusion even more away from the electrode.
How do you control sensitivity or selectivity of the 3D-printed electrodes? Are there certain electrodes better suited for in vivo experiments?
Right now, we have only played with the shape of the 3D printed electrodes and have not tried to change the surface chemistry to enhance sensitivity or selectivity. However, changes in shape can enhance trapping effects and secondary reactions, and these are useful in discriminating some catecholamines such as dopamine and epinephrine. For use in vivo, we need an electrode that strongly adheres to the wire, but the 3D printed electrodes are great for that purpose.
What are some other applications of the 3D-printed electrodes? How can this technology benefit the field?
3D-printed electrodes could be used in many other applications beyond in vivo neurochemistry. They could be used in cell culture studies to measure in synapses or near discrete cells. They could be used as imaging tips in scanning electrochemical microscopy (SECM) experiments. They could be used in other environments where small electrodes are needed because of size.