Quantification of Tyrosine in Pharmaceuticals with the New Biosensor Based on Laccase-Modified Polypyrrole Polymeric Thin Film

Abstract

Stress, a state of body tension, sometimes caused by increased levels of tyrosine (Tyr) in the body, can lead to serious illnesses such as depression, irritability, anxiety, damage to the thyroid gland, and insomnia. The body can be provided with an adequate concentration of tyrosine by taking pharmaceutical products or by dietary intake. Therefore, this study presents the development of a new enzyme sensor for the quantification of Tyr in pharmaceuticals. A screen-printed carbon electrode (SPCE) was modified with the conductive polymer (CP) polypyrrole (PPy) doped with hexacyanoferrate (II) anion (FeCN), the polymer having been selected for its excellent properties, namely, permeability, conductivity, and stability. The enzyme laccase (Lacc) was subsequently immobilized in the polymer matrix and cross-linked with glutaraldehyde, as this enzyme is a thermostable catalyst, greatly improving the performance of the biosensor. The electrochemical method of analysis of the new device, Lacc/PPy/FeCN/SPCE, was cyclic voltammetry (CV), and chronoamperometry (CA) contributed to the study of changes in the biosensor with doped PPy. CV measurements confirmed that the Lacc/PPy/FeCN/SPCE biosensor is a sensitive and efficient platform for Tyr detection. Thus, this enzyme sensor showed a very low limit of detection (LOD) of 2.29 × 10−8 M, a limit of quantification (LOQ) of 7.63 × 10−8 M, and a very high sensitivity compared to both devices reported in the literature and the PPy/FeCN/SPCE sensor. Quantitative determination in pharmaceuticals was performed in L-Tyr solution of different concentrations ranging from 0.09 to 7 × 10−6 M. Validation of the device was performed by infrared spectrometry (FT-IR) on three pharmaceuticals from different manufacturers and with different Tyr concentrations.

Development of a Chemically Modified Sensor Based on a Pentapeptide and Its Application for Sensitive Detection of Verbascoside in Extra Virgin Olive Oil

“…However, in the case of SPCE/GPHOX-Pentapeptide the Epa1-Epc1 and Epa2-Epc2 differences were always close to the theoretical value of 0.13 V corresponding to a reversible two-electron, two-proton mechanism, even for high scan rates. In the case of SPCE/GPHOX, as the scan rate increases, the intensity of the oxidation peak current increases linearly with the square root of the scan rate, consistent with oxidation limited by the diffusion of an active species in solution [ 73 ]. On the other hand, in the case of SPCE/GPHOX-Pentapeptide, as the scan rate increases, the intensity of the oxidation peak current also increases linearly with the scan rate, consistent with the electron-transfer-controlled oxidation process [ 74 ].…”

Nanomaterials as Redox Mediators in Laccase-Based Amperometric Biosensors for Catechol Assay

“…Among many recent advanced detection platforms, laccase-based biosensors are superior for their rapid, effective, and online use by in situ devices for the determination of phenolic compounds [ 19 , 20 , 21 , 22 , 23 ]. In enzyme-based biosensors, immobilization methods play a significant role.…”

“…Numerous nanostructured carriers have been developed to advance traditional enzyme immobilization strategies, including carbon nanotubes, graphene and its derivatives, nanoparticles, nanoflowers, and metal-organic frameworks with unique properties. These platforms for enzyme immobilization have a high surface-to-volume ratio, high surface area, robust chemical and mechanical stability, surface pendant functional groups, and outstanding electrical characteristics, resulting in a higher concentration and stabilization of the immobilized enzyme [ 3 , 12 , 19 , 20 , 21 ].…”

A facile method for generating polypyrrole microcapsules and their application in electrochemical sensing

“…[ 13 ] Thin films of polypyrrole have been used as supports for enzymes for their adsorptive properties. [ 14 ] If the load of polypyrrole is relatively high, it can increase the capacitance of the electrode, which can be useful for different electronic devices. [ 15 – 19 ]…”