Background.
Chemical signalling between cells is a fundamental component of life. Examples include quorum sensing in bacterial biofilms, paracrine signalling between immune cells, and neurotransmission. Chemical neurotransmission occurs when one neuron releases signalling molecules, called neurotransmitters (NTs), into the small gap between itself and an adjacent neuron, called a synapse (see schematic). After release, NTs are either taken up by the post-synaptic neuron or diffuse away into the extracellular space. When dopamine is the signalling molecule, this uptake and diffusion process plays a major role in the motor function, motivation, and reward systems, as well as disorders and diseases like Parkinson's, schizophrenia, and addiction. Significant progress has been made in our understanding of chemical neurotransmission from in vivo and in vitro studies in the past decades. However, there are still gaps in our understanding – especially at the sub-cellular level – because the analytical tools for studying these processes do not possess the required spatial and/or temporal resolution. |
Our approach.
We are developing light-addressable electrochemical sensors (LAES for short) to perform quantitative imaging of neurotransmitter movement around single neurons. LAES are powerful sensors because they allow us to selectively turn an electrochemical reaction on and off using light as a stimulus in both space and time. Simply put, the sensors behave like an electrochemical camera that provide detailed chemical images of NT release from single cells. The LAESs we make are based on Schottky junctions, which are formed between an electrochemically active metal (like Au) and a light-absorbing photoelectrode (like Si). |
To date, we have shown that we can build LAES using n-type Si and Au NPs. These sensors show excellent charge transfer kinetics towards outer-sphere redox species and are stable for a thousand CV cycles in aqueous media (~3.5 hours of cycling). We can also use them to quantitatively measure dopamine over a wide dynamic range (0.5 – 500 µM) with a fairly low limit of detection (~0.5 µM). We are actively working to better understand the semiconductor photoelectrochemistry and control the semiconductor/metal interface for improved sensing characteristics.
Publications.
This work is supported by grants from the National Science Foundation and a Cottrell Scholar Award from the Research Corporation for Science Advancement.
- Light-addressable electrochemical sensing with electrodeposited n-silicon/gold nanoparticle Schottky junctions. Terrero Rodríguez, I.M.; Borrill, A.J.; Schaffer, K.J.*; Hernandez, J.B.*; O'Neil, G.D. Anal. Chem. 2020, 92, 11444–11452.
- Square wave voltammetry enables measurement of light-activated oxidations and reductions on n-type semiconductor/metal junction light-addressable electrochemical sensors. Arthur, E.; Ali, H.*; Hussain, A.*; O'Neil, G.D. Anal. Chem. 2023
This work is supported by grants from the National Science Foundation and a Cottrell Scholar Award from the Research Corporation for Science Advancement.