A Review of Sensors and Biosensors Modified with Conducting Polymers and Molecularly Imprinted Polymers Used in Electrochemical Detection of Amino Acids: Phenylalanine, Tyrosine, and Tryptophan

Abstract

Recently, the studies on developing sensors and biosensors—with an obvious interdisciplinary character—have drawn the attention of many researchers specializing in various fundamental, but also complex domains such as chemistry, biochemistry, physics, biophysics, biology, bio-pharma-medicine, and bioengineering. Along these lines, the present paper is structured into three parts, and is aimed at synthesizing the most relevant studies on the construction and functioning of versatile devices, of electrochemical sensors and biosensors, respectively. The first part presents examples of the most representative scientific research focusing on the role and the importance of the phenylalanine, tyrosine, and tryptophan amino acids, selected depending on their chemical structure and their impact on the central nervous system. The second part is dedicated to presenting and exemplifying conductor polymers and molecularly imprinted polymers used as sensitive materials in achieving electrochemical sensors and biosensors. The last part of the review analyzes the sensors and biosensors developed so far to detect amino acids with the aid of conductor polymers and molecularly imprinted polymers from the point of view of the performances obtained, with emphasis on the detection methods, on the electrochemical reactions that take place upon detection, and on the electroanalytical performances. The present study was carried out with a view to highlighting, for the benefit of specialists in medicine and pharmacy, the possibility of achieving and purchasing efficient devices that might be used in the quality control of medicines, as well as in studying and monitoring diseases associated with these amino acids.

Underivatized Amino Acid Chromatographic Separation: Optimized Conditions for HPLC-UV Simultaneous Quantification of Isoleucine, Leucine, Lysine, Threonine, Histidine, Valine, Methionine, Phenylalanine, Tryptophan, and Tyrosine in Dietary Supplements

“…The accurate quantitative determination of AAs has been a long historical project with continuous improvements and innovations have been achieved. Several publications have reported AA analysis in foods and biological fluids using GC–MS, 42 capillary electrophoresis, 43 HILIC-MS/MS, 44 ion-paired LC–MS/MS, 45 electrochemical detection (CE), 46 ion exchange chromatography, 5 and HPLC. 47 , 48 Most of these methods depend on pre- or postcolumn derivatization to improve the detection sensitivity.…”

“…The accurate quantitative determination of AAs has been a long historical project with continuous improvements and innovations have been achieved. Several publications have reported AA analysis in foods and biological fluids using GC–MS, capillary electrophoresis, HILIC-MS/MS, ion-paired LC–MS/MS, electrochemical detection (CE), ion exchange chromatography, and HPLC. , Most of these methods depend on pre- or postcolumn derivatization to improve the detection sensitivity. However, elimination of derivatization steps attracts many researchers, and many studies have described the analysis of AAs without derivatization steps such as underivatized determination of free AAs in honey using LC–MS/MS, branched-chain AAs in maple syrup urine disease using LC–MS/MS, evaluation embryo viability using CE-MS, urine analysis by LC–MS/MS, ion exchange, CE-MS coupled to a porous layer-gold nanoparticle-modified chiral column, AAs and peptides in nutritive mixtures in the total parenteral nutrition solution, and online coupling of UV, fluorescence, and electrochemical detection .…”

Applications of MXene-Containing Polypyrrole Nanocomposites in Electrochemical Energy Storage and Conversion

“…Electrochemical sensors transform chemical reactions of target analytes on electrodes into electrical signals that cause conductivity, potential, or current changes . The conducting polymer such as PPy is an excellent choice for electrochemical sensors due to its remarkable electrical characteristics, customizable chemical structures, and ease of production. − Besides, conductive inorganic nanofillers such as MXene have strong conductivity, have a low bandgap, are simple to functionalize, and have a lot of active sites, making it ideal for sensors with high sensitivity and selectivity. , …”

Simultaneous Determination of Caffeic Acid and Ferulic Acid Using a Carbon Nanofiber-Based Screen-Printed Sensor

“…Such limitations make research on the selective determination of phenolic compounds a constant topic of interest. The selection of nanomaterials used in sensor development can make a difference, thus improving the results obtained [27]. To our knowledge, there are no studies aiming at the simultaneous determination of caffeic and ferulic acid by cyclic voltammetry; therefore, our study can be a starting point for further research in the simultaneous quantification of these polyphenols from different types of samples.…”