Recent Advancement in the Fabrication of Colorimetric and Fluorometric
Sensors for the Detection of Basic Amino Acids
Authors: Kumar Dishen , Dutta Srishti , Pandey Abhilash , Sahu Devanand , Sharma Vanshika , Patra Goutam Kumar 
Published: April 2024

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Due to the biological importance of amino acids, the development of optical probes for these compounds has become a popular research topic in
recent years. The amino acid fluorescence or colorimetric sensors are organized according to the reactions the amino acids go through and the
related structural classification. Works on reaction-based chemosensors are categorized as either imine formation, Michael addition, thiazinane or
thiazolidine formation, cleavage of a sulfonate ester, cleavage of a disulfide, metal complexes-displace coordination, or other mechanisms
depending on the mechanisms between sensors and amino acids.

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The majority of proteins are composed of amino acids (AA), which are tiny molecules with a variety of functional side chain groups. As a result,
amino acids play a number of different roles in physiological processes. This family member's histidine (His) is necessary for weight gain, tissue
growth, and repair. Another member of this family, lysine (Lys), is crucial for the Krebs-Henseleit cycle and polyamine production, and animals'
metabolic activities and weight gain depend on appropriate lysine intake. Tryptophan (Trp) is an essential component of biological processes like
protein synthesis, animal growth, and plant development because it regulates the transfer of metal elements in biological bases.

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Numerous attempts have been made to create new procedures for amino acid analysis as a result of the rising focus on human health, disease
diagnosis, and therapy. Currently, spectroscopic, chromatographic, or electrochemical analytical methods are most frequently employed to identify
and characterize amino acids. However, each method has certain disadvantages, such as the need for equipment and trained personnel, operational
simplicity, analytical cost, test speed, and detection.

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Based on the important distinguishing characteristics of various amino acids to date, much research has been done on optical probes using
indicator-displacement tests, metal complex coordination, particular interactions between probes and amino acids, and other techniques. We further
subdivided the reaction-based probes into the following groups: production of imines, Michael addition, thiazinane or thiazolidine, cleavage of
sulfonate ester, cleavage of disulfide, and others. Metal complexes-displace coordination. Due to some amino acids' similarity in structure and
reactivity, it is still challenging to develop sensors that can selectively and sensitively identify amino acids from one another, such as the three
biological thiols Cys, Hcy, and GSH.

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Specific reactions between probes and amino acids and other techniques have been extensively researched based on the significant characteristic
features of diverse amino acids to date. We further divided the reaction-based probes into the following categories: metal complexes-displace
coordination, imine creation, Michael addition, thiazinane or thiazolidine formation, cleavage of a sulfonate ester, cleavage of a disulfide; and
others.