A Noradrenaline Electrochemical Biosensor Based on Plasma Functionalized Multi-Walled Carbon Nanotubes (MWCNTs-NH ₂ )

Abstract

Despite their advantages, one limitation of biosensors is their reliance on biological systems, which can lead to lower reproducibility compared to purely chemical methods, and typically yield relative rather than absolute values. However, they offer significant benefits in terms of speed and cost, making them ideal for real-time or continuous monitoring. Importantly, biosensors respond specifically to biologically active pollutants, providing a direct correlation between the sensor’s response and the level of environmental toxicity [1]. Due to their distinctive physical and chemical characteristics, nanomaterials have become crucial in modern sensor design. They are used for covalent attachment of biomolecules, catalysis of electrochemical reactions, enhancing electron transfer, and molecular tagging. Their multifunctionality makes them indispensable in the construction of high-performance electrochemical sensors and biosensors [2,3]. Noradrenaline, also known as norepinephrine, is a chemical that acts as both a neurotransmitter and a hormone. It plays a crucial role in the body's "fight or flight" stress response by increasing heart rate and blood pressure. Noradrenaline is synthesized from dopamine and influences alertness, attention, and memory in the brain. Additionally, it contributes to sensory perception and behavioral responses to various stimuli. The immobilization of the enzyme tyrosinase on MWCNTs-NH 2 was utilized to measure noradrenaline concentrations in injections. The plasma-treated multi-walled carbon nanotubes (MWCNTs-NH 2 ) were prepared from raw MWCNTs according to the process described in the literature [4]. A straightforward method was developed to prepare a modified electrode with functionalized carbon nanotubes. Tyrosinase was immobilized onto the surface of the MWCNTs-NH 2 /glassy carbon electrode. Voltammograms taken in an aqueous solution indicated that the functionalized carbon nanotubes enhanced the direct electron transfer of the immobilized enzyme, resulting in the observation of a stable redox couple. Tyrosinase is capable of catalyzing the oxidation of noradrenaline to related quinone. Upon adding noradrenaline to the electrochemical cell, the oxidation peak current of the prepared electrochemical biosensor increased, producing a catalytic current. Based on these findings, a biosensor for the determination of noradrenaline has been developed. This method demonstrated sufficient accuracy, sensitivity, and precision. Additionally, the biosensor exhibited good repeatability and stability for assessing noradrenaline in both bulk form and pharmaceutical dosage forms. References: R. Singh, R. Gupta, D. Bansal, R. Bahateria, M. Sharma, ACS Omega9 (2024) 7336-7356. A. Bayandori Moghaddam, Micro Nano Lett. 12 (2017) 425-429. S. Wang, Y. Liu, A. Zhu, Y. Tian, Anal. Chem. 95 (2023) 388-406 Y. Wei, R. Yang, X. Chen, L. Wang, J.-H. Liu, X.-J. Huang, Anal. Chim. Acta, 755 (2012) 54-61.