(92d) Dopamine Modified Carbon Fiber Micro-Electrodes for Enhanced Detection of Cu(II) Via Fast Scan Cyclic Voltammetry

Neurological disorders (NDs) affect millions of people globally despite the meticulous efforts of the medical community to limit their progression. The lack of efficient drugs to address NDs underlines the need for a deeper understanding of the etiology of these diseases, to develop effective medications. One such aspect is the effect of external factors such as heavy metals on the progression of NDs. Cu(II) when present in excess is known to play a pivotal role in NDs such as Alzheimer’s disease. Copper’s ability to cycle between oxidation states when bound to amyloid-β aggregates leads to an overproduction of reactive oxidative species, causing irreversible oxidative damage. Therefore, it is important to monitor the levels of Cu(II) in neurological systems to increase the understanding of its impact on NDs.

Many analytical tools have been developed to detect trace amounts of Cu(II). However, conventional methods such as spectrometry, chromatography, immunoassays, and colorimetry analyze blood or urine samples or postmortem tissues. These methods are not translatable to living organisms and limit access to real-time information. Thus, there is a critical need to develop a sensor with a high temporal and spatial resolution to study the changes of heavy metals such as Cu(II) in living systems in real-time. In recent years, electrochemists have made a breakthrough in developing sensors targeted toward detecting the real-time concentration of toxic metals. However, most of the reported electrode fabrication used to enhance the sensitivity are not bio-compatible, making them a poor choice for in vivo measurements. Therefore, the development of a cheap and bio-compatible surface modification for detecting physiological concentrations of metals ions in vivo will largely aid in bridging the knowledge gap in understanding the vital roles heavy metals play in NDs.

This study uses fast-scan cyclic voltammetry (FSCV) with dopamine-modified carbon fiber microelectrodes (CFMs) for the detection of trace amounts of Cu(II). Mussel-inspired chemistry has shown that dopamine can be used as a surface modification by mimicking the strong adhering abilities of the marine mussel. The CFM was fabricated by the electrodeposition of dopamine, making it a bio-compatible surface modification that is ideal for in vivo measurements. All the experiments were performed in tris buffer, which mimics cerebellum fluid. We optimized the electrodeposition process by characterizing the electrochemistry of dopamine with our sensor and selecting the best time for electrodeposition based on FSCV experimental results and the surface morphology of the electrodes observed using atomic force microscopy. We characterized the sensor for the detection of Cu(II) with and without surface modification and find that there is a significant increase in the sensitivity of the dopamine-modified CFM. We also performed stability and shelf-life tests to examine the analytical performance of our sensor for prolonged usage.

The bio-compatible nature of the dopamine surface modification coupled with enhanced sensitivity and the high temporal and spatial resolution provided by FSCV allows us to make fast in vivo measurements and promises great potential for further development into a powerful analytical tool for the detection of Cu(II) in neurological systems. Future studies will focus on extending this research toward other toxic metals and developing a multichannel system for the simultaneous detection of neurotransmitters and toxic metals.