Review. Electrochemical sensors used in the determination of L ‐Dopa

New zinc(ii) metalloporphyrin: molecular structure, spectroscopic characterization, electrochemical sensing of dopamine, and catalytic dye degradation

This work is a continuation of the series of studies aimed at studying the electronic and structural properties of divalent metal porphyrin complexes, especially zinc(ii) metalloporphyrins. In this perspective, we have prepared the [Zn(TMPP)(4,4'-bpy)]·CHCl3 (I) coordination compound, where TMPP is the meso-tetra(para-methoxyphenyl)porphyrinate and 4,4'-bpy is the 4,4'-bipyridine. The UV/Vis, fluorescence, IR and 1H NMR spectroscopic techniques, ESI-HRMS mass spectrometry investigation as well as a single crystal X-ray diffraction study were used to characterize the title compound. Notably, we demonstrated the ability of this zinc(ii) metalloporphyrin to degrade the methylene blue (MB) dye, examining several influencing factors, including pH, temperature and initial dye concentration. Additionally, complex I exhibited remarkable efficiency in degrading MB under blue LED irradiation. Beyond catalytic applications, this compound was successfully employed as an electrochemical sensor for the detection of dopamine (DA) using the square wave voltammetry (SWV) method, showcasing its multifunctional capabilities.

Recent advances in molecularly imprinted polymer-based electrochemical sensors

Molecularly imprinted polymers (MIPs) are the equivalent of natural antibodies and have been widely used as synthetic receptors for the detection of disease biomarkers. Benefiting from their excellent chemical and physical stability, low-cost, relative ease of production, reusability, and high selectivity, MIP-based electrochemical sensors have attracted great interest in disease diagnosis and demonstrated superiority over other biosensing techniques. Here we compare various types of MIP-based electrochemical sensors with different working principles. We then evaluate the state-of-the-art achievements of the MIP-based electrochemical sensors for the detection of different biomarkers, including nucleic acids, proteins, saccharides, lipids, and other small molecules. The limitations, which prevent its successful translation into practical clinical settings, are outlined together with the potential solutions. At the end, we share our vision of the evolution of MIP-based electrochemical sensors with an outlook on the future of this promising biosensing technology.

Smartphone-based detection of levodopa in human sweat using 3D printed sensors

Parkinson's disease (PD) is one of the leading neurological disorders negatively impacting health on a global scale. Patients diagnosed with PD require frequent monitoring, prescribed medications, and therapy for extended periods as symptom severity worsens. The primary pharmaceutical treatment for PD patients is levodopa (L-Dopa) which reduces many symptoms experienced by PD patients (e.g., tremors, cognitive ability, motor dysfunction, etc.) through the regulation of dopamine levels in the body. Herein, the first detection of L-Dopa in human sweat using a low-cost 3D printed sensor with a simple and rapid fabrication protocol combined with a portable potentiostat wirelessly connected to a smartphone via Bluetooth is reported. By combining saponification and electrochemical activation into a single protocol, the optimized 3D printed carbon electrodes were able to simultaneously detect uric acid and L-Dopa throughout their biologically relevant ranges. The optimized sensors provided a sensitivity of 83 ± 3 nA/μM from 24 μM to 300 nM L-Dopa. Common physiological interferents found in sweat (e.g., ascorbic acid, glucose, caffeine) showed no influence on the response for L-Dopa. Lastly, a percent recovery of L-Dopa in human sweat using a smartphone-assisted handheld potentiostat resulted in the recovery of 100 ± 8%, confirming the ability of this sensor to accurately detect L-Dopa in sweat.

Eu2O3@Cr2O3 Nanoparticles-Modified Carbon Paste Electrode for Efficient Electrochemical Sensing of Neurotransmitters Precursor L-DOPA

There are ten million people in the world who have Parkinson's disease. The most potent medicine for Parkinson's disease is levodopa (L-DOPA). However, long-term consumption of L-DOPA leads to the appearance of side effects, as a result of which the control and monitoring of its concentrations are of great importance. In this work, we have designed a new electrochemical sensor for detecting L-DOPA using a carbon paste electrode (CPE) modified with Eu2O3@Cr2O3 composite nanoparticles. Rare earth elements, including Eu, are increasingly used to design new electrode nanocomposites with enhanced electrocatalytic properties. Europium has been considered a significant lanthanide element with greater redox reaction behavior. We conducted a hydrothermal synthesis of Eu2O3@Cr2O3 and, for the first time, the acquired nanoparticles were used to modify CPE. The proposed Eu2O3@Cr2O3/CPE electrode was investigated in terms of its electrocatalytic properties and then used to develop an analytical method for detecting and quantifying L-DOPA. The proposed sensor offers a wide linear range (1-100 µM), high sensitivity (1.38 µA µM-1 cm-2) and a low detection limit (0.72 µM). The practical application of the proposed sensor was investigated by analyzing commercially available pharmaceutical tablets of L-DOPA. The corresponding results indicate the excellent potential of the Eu2O3@Cr2O3/CPE sensor for application in real-time L-DOPA detection.

N-Methylfulleropyrrolidine-Based Multimode Sensor for Determination of Butoconazole Nitrate

A multimode sensor (a sensor responding simultaneously to more than one mode, e.g., stochastic mode, amperometric mode, voltammetric mode) based on graphite paste modified with N-methylfulleropyrrolidine was proposed for the determination of butoconazole nitrate in its pharmaceutical formulation. The stochastic mode and square wave voltammetry mode were applied for the determinations. Both the stochastic mode and square wave voltammetry mode were applied for a qualitative and quantitative assay of butoconazole nitrate. The sensor can be used between 1.68 × 10^-6 and 1.68 × 10⁴ μmol L^-1 when the stochastic mode is used and between 0.168 and 16.80 μmol L^-1 when the square wave voltammetry mode is used. The multimode sensor was reliably used for the determination of butoconazole nitrate in its pharmaceutical formulation, Gynofort cream, the recorded recoveries being higher than 99.00%, with RSD (%) values of lower than 2.00%.