Electrochemical sensing of hydrogen peroxide using a glassy carbon electrode modified with multiwalled carbon nanotubes and zein nanoparticle composites: application to HepG2 cancer cell detection.

A nanobiocomposite was prepared from multiwalled carbon nanotubes and zein nanoparticles. It was dispersed in water/ethanol and drop cast onto a glassy carbon electrode. The modified electrode can be used for electroreduction of H2O2 (typically at a working potential of -0.71 V vs. Ag/AgCl). The electrochemical properties of the electrode were investigated by cyclic voltammetry, linear sweep voltammetry, chronoamperometry and electrochemical impedance spectroscopy. Response to H2O2 is linear in the 0.049 to 22 µM concentration range, and the detection limit is 35 nM at pH 7.0. The sensor was successfully utilized for the measurement of H2O2 in a synthetic urine sample, and for monitoring the release of H2O2 from human dermal fibroblasts and human hepatocellular carcinoma cells. Graphical abstractSchematic representation of a novel metal- and enzyme-free electrochemical nanosensor. A glassy carbon electrode was modified with a nanocomposite prepared from multiwalled carbon nanotubes and zein nanoparticles. It was applied to the identification of liver cancer cells via sensing of H2O2 and has a very low detection limit.

Preparation of tetraheptylammonium iodide-iodine graphite-multiwall carbon nanotube paste electrode: electrocatalytic determination of ascorbic acid in pharmaceuticals and foods.

The present work describes the construction of a new modified graphite-multiwall carbon nanotube paste electrode by casting the appropriate mixture of tetraheptylammonium iodide-iodine as a new modifier. The modified paste electrode was used for the determination of ascorbic acid (AA) in a phosphate buffer solution (pH 2.0). When compared to activated carbon, a graphite and multiwall carbon nanotube paste electrode containing a new modifier, the proposed modified paste electrode not only shifted the oxidation potential of AA towards a less-positive potential but also enhanced its oxidation peak current. Further, the oxidation of AA was highly stable at the modified paste electrode. The optimum analytical conditions were sought. The current response of AA increases linearly while increasing its concentration from 5.6 × 10(-5) to 1.2 × 10(-2) M with a correlation coefficient of 0.9991; the detection limit (3σ) was found to be of 3.6 × 10(-5) M. The present modified paste electrode was also successfully used for the determination of AA in the presence of common interference compounds. The present modified electrode was successfully demonstrated towards the determination of AA in pharmaceutical and food samples.