Recent Advances in Electrochemical and Optical Sensors for Detecting Tryptophan and Melatonin

Abstract

Tryptophan and melatonin are pleiotropic molecules, each capable of influencing several cellular, biochemical, and physiological responses. Therefore, sensitive detection of tryptophan and melatonin in pharmaceutical and human samples is crucial for human wellbeing. Mass spectrometry, high-performance liquid chromatography, and capillary electrophoresis are common methods for both tryptophan and melatonin analysis; however, these methods require copious amounts of time, money, and manpower. Novel electrochemical and optical detection tools have been subjects of intensive research due to their ability to offer a better signal-to-noise ratio, high specificity, ultra-sensitivity, and wide dynamic range. Recently, researchers have designed sensitive and selective electrochemical and optical platforms by using new surface modifications, microfabrication techniques, and the decoration of diverse nanomaterials with unique properties for the detection of tryptophan and melatonin. However, there is a scarcity of review articles addressing the recent developments in the electrochemical and optical detection of tryptophan and melatonin. Here, we provide a critical and objective review of high-sensitivity tryptophan and melatonin sensors that have been developed over the past six years (2015 onwards). We review the principles, performance, and limitations of these sensors. We also address critical aspects of sensitivity and selectivity, limit and range of detection, fabrication process and time, durability, and biocompatibility. Finally, we discuss challenges related to tryptophan and melatonin detection and present future outlooks.

Oxidation Mechanism of 1‐Methyl‐tryptophan and Tryptophan on Glassy Carbon Electrode: A Comparative Study

“…All electrochemical data presented here, Figures 1–5, and previous results from the literature for the oxidation of Trp in aqueous media [14–17, 22, 23, 29–31], were used to propose a mechanism for the electro‐oxidation of 1‐mTrp in aqueous medium on GCE, Scheme 2.…”

“…Our interest in the electroanalysis of Trp using DPV at GCE comes from a large number of works on modified GCEs [14][15][16][17]. To our knowledge there is no analytical data available for oxidation of Trp on GCEs, such as limit of detection, sensitivity and the range of linear response.…”

“…This occurs in two successive irreversible pH-dependent steps: a first stage with the formation of 2-oxyindolalanine; and a second step where this is electro-oxidized to form two electroactive products (quinone derivatives) [23]. Several electroanalytical methodologies with low detection limits, using modified electrodes, mainly with nanostructures, have been explored for the quantification of Trp [14][15][16][17]. However, to our knowledge so far, no work has quantified Trp on the bare GCE, without modification; and no comparison parameter in relation to the modified electrodes already proposed has been established.…”

A paper-based colourimetric sensor for sodium sulfite detection in beverages

“…Furthermore, the colourimetric response is well-suited to interpret rapid detection, especially in resource-constrained settings or underdeveloped countries [17]. Filter paper has become increasingly useful in developing sensors in recent years due to its wicking capacity [18].…”

Rational Design of Nanostructured Copper Phosphate Nanoflakes Supported Niobium Carbide for the Selective Electrochemical Detection of Melatonin

“…Thus, because of concern about the effect on the endocrine system and other metabolism, MLT detection is necessary . Many detection techniques are available and utilized as micellar electro kinetic chromatography, colorimetric, electrochemical sensing, radioimmunoassay (RIA), chemiluminescence (CL), spectrofluorometric, and many more. − …”