ascorbic-acid and phosphonic-acid

In this work, an Au electrode modified with self-assembled monolayers (SAMs) of 3-thienylphosphonic acid (TPA) was used as a novel functional interface to selectively sense dopamine (DA) in the presence of excess ascorbic acid (AA). Ellipsometry, X-ray photoelectron spectroscopic (XPS) and electrochemical measurements proved the immobilization of TPA on the gold surface. Interestingly, the Au electrode modified with TPA substantially improved the antifouling and renewal capabilities towards the oxidation of dopamine (DA) after 15 days of storage in undeoxygenated phosphate buffer solution (PBS pH 7.4). Moreover, the TPA-SAMs modified Au electrode could afford a selective electrochemical response for the DA oxidation in the presence of ascorbic acid (AA). Based on this result, a high sensitive detection limit of 2.0 × 10

Topics: Ascorbic Acid; Biofouling; Dopamine; Electrochemistry; Electrodes; Gold; Phosphorous Acids; Surface Properties

A novel hypoxanthine biosensor fabricated by immobilizing the xanthine oxidase (XOD) onto the phosphonic acid-functionalized silica (SiO2-P) film on the surface of glassy carbon electrode (GCE) was designed and constructed in this work. A biomimetic platform was designed with the phosphonic acid-functionalized silica nanoparticles (SiO2-P NPs) synthesized by the method of reverse microemulsion and electrostatic binding. In such a platform, XOD was selected as model protein to fabricate hypoxanthine biosensor based on SiO2-P NPs. The nanocomposite was characterized with transmission electron microscopy (TEM), energy dispersive X-ray spectrometer (EDS) and electrochemical impedance spectroscopy (EIS). Based on the advantageous functions of SiO2-P NPs, the entrapped XOD could preserve its bioactivity and exhibited an excellent electrochemical behavior with a formal potential of -0.37 V in phosphate buffer solution (PBS, pH=7). Response studies to hypoxanthine were carried out using current-time response curve. The biosensor exhibited a wide linear response ranging from 1.00×10(-6) to 2.61×10(-4) M. The detection limit of 2.33×10(-7) M at a signal-to-noise ratio of 3 was lower than that most reported previously. In addition, the electrode modified with XOD/(SiO2-P NPs) film also had a strong anti-interference ability in the presence of uric acid (UA) and ascorbic acid (AA). The assay results of hypoxanthine in fish samples were in a good agreement with the reference values.

Topics: Animals; Ascorbic Acid; Biocompatible Materials; Biosensing Techniques; Carbon; Carps; Electrochemical Techniques; Electrodes; Enzymes, Immobilized; Humans; Hypoxanthine; Limit of Detection; Milk; Nanoparticles; Phosphorous Acids; Signal-To-Noise Ratio; Silicon Dioxide; Uric Acid; Xanthine Oxidase