Electroanalytical Sensing of Melatonin and its Applications in Pharmaceutics and Biology

Abstract

Melatonin (N-acetyl-5-methoxytryptamine) is a neuroendocrine hormone produced in the pineal gland and distributed throughout the body. It has an important role in human physiology in synchronizing biological processes in neuroscience for regulating sleep and mood, and in clinical diagnosis for managing sleep disorders and exploring its therapeutics. However, melatonin recently received special attention because it has been proposed as an adjuvant in treating SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2), the coronavirus responsible for the COVID-19 pandemic. Therefore, the sensitive detection of melatonin in pharmaceutical samples and biological fluids (such as blood, saliva, breast milk, and urine) is important to ensure proper dosage or optimize treatment and to determine endogenous levels, even in pharmacological research and safety. In that sense, this review focuses on the recent development of electrochemical sensors for melatonin, emphasizing the use of modified electrodes to enhance sensitivity and selectivity. Different electrode materials, including screen-printed carbon (SPE), glassy carbon (GC), boron-doped diamond (BDD), and carbon paste electrodes (CPE), are explored for their effectiveness in melatonin detection. Additionally, the application of voltammetric techniques, such as differential pulse voltammetry (DPV) and square wave voltammetry (SWV) is highlighted for their ability to provide high-resolution detection with minimal interference. Other electrochemical techniques, including cyclic voltammetry (CV) and chronoamperometry (CA), are also discussed in their role for melatonin sensing. These electrochemical techniques provide significant benefits, such as fast, sensitive, and affordable detection, making them essential tools in pharmaceuticals, clinical diagnostics, and biological research. On the other hand, this article explores the detection of synthetic melatonin, both individually and in the presence of interfering substances, such as serotonin, dopamine, and acetaminophen, with a focus on the challenges and techniques for distinguishing melatonin from other compounds in complex biological matrices, such as urine, blood, saliva, and pharmaceutical tablets.