(Digital Presentation) Electrochemical Glutamate Sensor Using Copper Oxide Nanomaterials Functionalized with Multiwall Carbon Nanotubes

Glutamate is the most abundant neurotransmitter in the central nervous system (CNS) and plays an important role in different physiological processes. Excess amounts of glutamate cause excitotoxicity resulting in different diseases such as Alzheimer’s and glioma, pain disorders, spinal cord injuries, and cancer 1-4 . The concentration of glutamate in body fluids such as saliva is associated with those diseases. Therefore, glutamate is a potential biomarker for pathologies. By measuring glutamate levels in biofluids these pathologies can be monitored. Lab-based techniques such as liquid chromatography and gas chromatography offer a low limit of detection, high sensitivity, and precise detection of biomarkers 4-7 . These techniques are expensive, bulky, time-consuming, and require skilled personnel to operate them and therefore are not suitable for wearable and personalized healthcare applications. In contrast, electrochemical sensors are simple, low-cost, handy, and offer rapid and high sensing performance of biomarkers/analytes 8,9 . In this work, we fabricated a very simple, low-cost, and reusable enzyme-free electrochemical sensor using copper oxide (CuO) nanomaterials for label-free detection of glutamate. CuO nanomaterials were synthesized by a low-cost wet chemical process. The CuO nanomaterials were dispersed in DI water and the working electrode was prepared by drop casting of CuO dispersion on a screen-printed carbon electrode (SPCE). Multiwall carbon nanotubes (MWCNTs) were used with CuO to enhance the electron transfer from CuO to SPCE (Figure a). Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) were used to perform glutamate sensing in deionized (DI) water at pH 7.4. The peak oxidation current ( I pa ) is proportional to glutamate (G) presence in DI water (Figure b). The sensor showed good oxidation current event at a low concentration of glutamate (20 µM) in DI water. The normal concentrations of glutamate in body fluids such as plasma and saliva are about 5-100 µM, and 1-30 µM respectively 3 . Therefore, CuO nanostructure-based nonenzymatic electrochemical sensor is very potential for low cost, portable, rapid detection of glutamate in those body fluids. We will further discuss details of CuO synthesis, electrode fabrication process, sensing mechanism, and challenges of the glutamate sensor. References Lewerenz and P. Maher, Frontiers in neuroscience. 9 (2015) 469. Takano et al., Nature medicine. 7 (2001) 1010-1015. H Jasim et al., Scientific reports 8.1 (2018): 1-9. Schultz, Z. Uddin, G. Singh, and M. M. Howlader, Analyst. 145 (2020) 321-347. Klimuntowski, M. M. Alam, G. Singh, and M. M. Howlader, ACS Sensor. 5(3) (2020) 620–636. Budczies et al., International journal of cancer. 136 (2015) 1619-1628. Xin et al, Chinese Journal of Analytical Chemistry. 35 (2007), 1151-1154. Hughes et al., Sensors and Actuators B: Chemical. 216 (2015) 614-621. Rocchitta et al., Sensors, 16 (2016) 780. X Zhang et al., The Journal of Physical Chemistry C 112.43 (2008): 16845-16849. Y Li et al., Materials Research Bulletin 43.8-9 (2008): 2380-2385. RP Allaker, and Z Yuan, Nanobiomaterials in clinical dentistry. Elsevier, 2019. 243-275. Figure 1