Electrochemical Determination of Tyrosine in the Presence of Dopamine and Uric Acid at the Surface of Gold Nanoparticles Modified Carbon Paste Electrode

Decorated graphene oxide with gold nanoparticles as a sensitive modified carbon paste electrode for simultaneous determination of tyrosine and uric acid

It is presented here as a simple, selective, rapid, low-cost, with a wide linear range method to simultaneously determine tyrosine and uric acid using a modified carbon paste electrode decorated with graphene oxide and gold nanoparticles (GO/AuNPs/MCPE). In order to characterize and evaluate the morphology and constituents of the nanostructures, X-ray diffraction spectroscopy, Transmission electron microscopes, Dynamic light scattering, Zeta potential, electrochemical impedance spectroscopy, and Voltammetry were employed. The current response on the surface of the modified electrode had a dynamic linear range relationship in the concentrations of 0.14-340.00 µmol L-1 and 0.06-141.00 µmol L-1 for tyrosine and uric acid, respectively, and the method detection limit (MDL) was 0.0060 µmol L-1 and 0.0037 µmol L-1, respectively. This modified electrode provided high stability, sensitivity, and acceptable reproducibility for voltammetric measurements of tyrosine and uric acid simultaneously in a biological matrix.

Development of Polypyrrole Modified Screen-Printed Carbon Electrode Based Sensors for Determination of L-Tyrosine in Pharmaceutical Products

Good health, of vital importance in order to carry out our daily routine, consists of both physical and mental health. Tyrosine (Tyr) deficiency as well as its excess are issues that can affect mental health and can generate disorders such as depression, anxiety, or stress. Tyr is the amino acid (AA) responsible for maintaining good mental health, and for this reason, the present research presents the development of new electrochemical sensors modified with polypyrrole (PPy) doped with different doping agents such as potassium hexacyanoferrate (II) (FeCN), sodium nitroprusside (NP), and sodium dodecyl sulfate (SDS) for a selective and sensitive detection of Tyr. The development of the sensors was carried out by chronoamperometry (CA) and the electrochemical characterization was carried out by cyclic voltammetry (CV). The detection limits (LOD) obtained with each modified sensor were 8.2 × 10-8 M in the case of PPy /FeCN-SPCE, 4.3 × 10-7 M in the case of PPy/NP-SPCE, and of 3.51 × 10-7 M in the case of PPy/SDS-SPCE, thus demonstrating a good sensitivity of these sensors detecting L-Tyr. The validation of sensors was carried out through quantification of L-Tyr from three pharmaceutical products by the standard addition method with recoveries in the range 99.92-103.97%. Thus, the sensors present adequate selectivity and can be used in the pharmaceutical and medical fields.

Enzymatic-induced upconversion photoinduced electron transfer for sensing tyrosine in human serum

This paper reports a novel nanosensor for tyrosine based on photoinduced electron-transfer (PET) between NaYF4:Yb, Tm upconversion nanoparticles (UCNPs) and melanin-like polymers. Melanin-like films were obtained from catalytic oxidation of tyrosine by tyrosinase, and deposited on the surface of UCNPs, and then quenched the fluorescence of UCNPs. Under the optimized conditions, the fluorescence quenching of UCNPs showed a good linear response to tyrosine concentration in the range of 0.8-100 μΜ with a detection limit of 1.1 μΜ. Meanwhile, it showed good sensitivity, stability and has been successfully applied to the detection of tyrosine in human serum.