Electrochemical Sensors for Simultaneous Determination of Small Biomolecules By 3D Layered Hollow Honeycomb-like Ni-NiO@CPVP Modified Glassy Carbon Electrode

A Novel Electrochemical Sensor Based on Pd Confined Mesoporous Carbon Hollow Nanospheres for the Sensitive Detection of Ascorbic Acid, Dopamine, and Uric Acid

In this study, we designed a novel electrochemical sensor by modifying a glass carbon electrode (GCE) with Pd confined mesoporous carbon hollow nanospheres (Pd/MCHS) for the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The structure and morphological characteristics of the Pd/MCHS nanocomposite and the Pd/MCHS/GCE sensor are comprehensively examined using SEM, TEM, XRD and EDX. The electrochemical properties of the prepared sensor are investigated through CV and DPV, which reveal three resolved oxidation peaks for AA, DA, and UA, thereby verifying the simultaneous detection of the three analytes. Benefiting from its tailorable properties, the Pd/MCHS nanocomposite provides a large surface area, rapid electron transfer ability, good catalytic activity, and high conductivity with good electrochemical behavior for the determination of AA, DA, and UA. Under optimized conditions, the Pd/MCHS/GCE sensor exhibited a linear response in the concentration ranges of 300-9000, 2-50, and 20-500 µM for AA, DA, and UA, respectively. The corresponding limit of detection (LOD) values were determined to be 51.03, 0.14, and 4.96 µM, respectively. Moreover, the Pd/MCHS/GCE sensor demonstrated outstanding selectivity, reproducibility, and stability. The recovery percentages of AA, DA, and UA in real samples, including a vitamin C tablet, DA injection, and human urine, range from 99.8-110.9%, 99.04-100.45%, and 98.80-100.49%, respectively. Overall, the proposed sensor can serve as a useful reference for the construction of a high-performance electrochemical sensing platform.

Electrochemical determination of purine and pyrimidine bases using a 1,10-phenanthroline-Fe3O4 nanoparticles-graphene oxide-chitosan nanocomposite

A 1,10-phenanthroline-Fe₃O₄ nanoparticles-graphene oxide-chitosan nanocomposite (Phen-Fe₃O₄ NPs-GO-Chi) was fabricated and used to modify a glassy carbon (GC) electrode. The modified surface of the electrode was characterized by field emission-scanning electrochemical microscopy. Then, the prepared electrode was used as a sensor for simultaneous determination of purine and pyrimidine bases in DNA. The Phen-Fe₃O₄ NPs-GO-Chi composite modified electrode showed excellent response toward guanine (G), adenine (A), thymine (T) and cytosine (C). The sensor displayed higher effective surface, an appropriate peak-to-peak separation, and a larger peak current compared to the bare electrode. The evaluated detection limits of G, A, T, and C concentrations are 12, 4, 22, and 9 μM over the concentration range of 15-500, 15-400, 40-1000 and 40-1400 μM, respectively. In addition, the results show that the modified electrode is stable for 7 days and has good repeatability and interfering molecules and ions have no significant effect on peak current. The proposed method was successfully applied for the determination of purine and pyrimidine bases in a fish DNA sperm sample as a real sample.

Ti3C2Tx (MXene)/Pt nanoparticle electrode for the accurate detection of DA coexisting with AA and UA

Dopamine (DA), uric acid (UA) and ascorbic acid (AA) are biomolecules widely distributed in the human body and play an important role in many physiological processes. An abnormal concentration of them is associated with various diseases. Thus, the accurate and fast detection of them has been one of the major demands in the healthcare industry. In this study, we demonstrate that Ti₃C₂T_x/PtNP modified glassy carbon electrodes (GCEs) show a good electrochemical performance in the detection of DA and UA. However, there is no response signal to AA for either the CV or DPV curve due to the electrostatic repulsion between the negatively charged electrode surface and the negatively charged AA. Ti₃C₂T_x(MXene)/Pt nanoparticles (PtNPs) are prepared by etching Ti₃AlC₂(MAX) with HF and reducing H₂PtCl₆ with a NaBH₄ aqueous solution. The morphology of Ti₃C₂T_x/PtNPs is multilayered accordion-like Ti₃C₂T_x decorated with PtNPs with a diameter of 10-20 nm. Furthermore, it is found that the electrochemical detection of DA will be enhanced by AA. The electrochemical detection rule of AA enhanced DA can be expressed as follows: I_(DA+AA) = 0.011216C_AA + 0.039950C_DA + 1.1175(I_(DA+AA) is the peak current of DA coexisting with AA. C_AA is the concentration of AA. C_DA is the concentration of DA). This can be used as a calibration to correct the concentration of DA when AA and DA coexist. Notably, AA promotes the stability of the electrode because it cleans the oxidation products from the electrode surface in time. In addition, the sensor exhibits good reproducibility and satisfactory recovery results in a real sample.