Nonenzymatic L-lysine amino acid detection using titanium oxide nanoparticles/multi wall carbon nanotube composite electrodes

For the first time, a nonenzymatic electrochemical sensor for the detection of lysine was proposed based on immobilizing Multi wall carbon nanotube (MWCNT) and Titanium oxide nanoparticles (TiO2NPs) on glassy carbon (GC) electrode. Scaning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS) were used to confirm the successful stepwise assembly procedure of the sensor. The electrocatalytical behaviors of the sensor were also investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results showed that MWCNT- TiO2NPs exhibited a remarkable electrocatalytic activity for the oxidation of lysine. Under optimal conditions, the DPV response of the sensor was proportional to the lysine concentration in the range of 500 to 5500 nanomolar with a detection limit and sensitivity of 390 nM and 0.1795 μAμM−1. This electrode show many advantages such as simple preparation without using any enzyme special electron transfer mediator or specific reagent, excellent catalytic activity at physiological pH values and antifouling property toward lysine and its oxidation product. Furthermore, the selectivity of the proposed sensor was tested in the presence of some amino acids and the response of the sensor was encountered with interferences of proline and tryptophan at equimolar concentrations.

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