Mounir Ben Ali

A novel amperometric biosensor based on gold nanoparticles anchored on reduced graphene oxide for sensitive detection of l-lactate tumor biomarker

In this work, a novel amperometric biosensor based on gold nanoparticles anchored on reduced graphene oxide (RGO-AuNPs) and l-lactate dehydrogenase (LDH) was developed for the sensing of l-lactate. Firstly, the RGO-AuNPs modified screen printed electrodes were tested for NADH detection showing a wide dynamic range and a low detection limit. Next, the biosensor was constructed by incorporating both enzyme and RGO-AuNPs in a sol gel matrix derived from tetrametoxysilane and methyltrimetoxysilane. The enzyme loading, working pH, and coenzyme concentration were optimized. The biosensor linearly responded to l-lactate in the range of 10µM-5mM and showed a good specific sensitivity of 154µA/mMcm(2) with a detection limit of 0.13µM. This was accompanied by good reproducibility and operational stability. Tests on artificial serum proved that l-lactate can be determined practically without interferences from commonly interfering compounds such as urate, paracetamol and l-ascorbate. Our LDH/RGO-AuNPs/SPCE based biosensor thus performs as electrochemical device for the detection of l-lactate as a viable early cancer bio-marker.

Novel Sensitive Impedimetric Microsensor for Phosphate Detection Based on a Novel Copper Phthalocyanine Derivative

ABSTRACT A novel electrochemical impedimetric sensor based on new copper phthalocyanine derivative-functionalized gold substrates has been developed. The modified transducers have been characterized using Fourier transform infrared spectroscopy and contact angle measurements. Under the optimized conditions in terms of polarization and frequency range, the developed sensor provided a large linear range from 1 × 10−10 to 1 × 10−3 M with a detection limit of 9.48 × 10−11 M. To minimize the impedimetric sensor’s size, a microsensor based on modified gold microelectrodes was developed. Good sensitivity in the range from 1 × 10−8 to 1 × 10−3 M with a limit of detection of 8.32 × 10−9 M was achieved.

Amperometric Determination of Ethanol using a Novel Nanobiocomposite

ABSTRACT A novel amperometric biosensor for the determination of ethanol through one-step drop coating of a nanobiocomposite on a glassy carbon electrode is presented. The measurement of ethanol concentration is based on the production of reduced form of the β-nicotinamide adenine dinucleotide (NADH), which is the product of enzymatic reaction catalyzed by alcohol dehydrogenase. The enzyme was immobilized in a polystyrene sulfonate-multiwalled carbon nanotube composite that offers a stable environment for alcohol dehydrogenase. The performance of polystyrene sulfonate–multiwalled carbon nanotube–alcohol dehydrogenase nanobiocomposite–modified glassy carbon electrode was evaluated by cyclic voltammetry, electrochemical impedance spectroscopy, and amperometry. Enzymatic oxidation of ethanol was realized in the presence of NAD+ and was determined amperometrically. The concentrations of NAD+ and enzyme were optimized. Ethanol determination was performed using 7 IU alcohol dehydrogenase/electrode in the presence of 5 mM NAD+ in pH 8.8 pyrophosphate buffer. The polystyrene sulfonate–multiwalled carbon nanotube–alcohol dehydrogenase/glassy carbon electrode biosensor showed high sensitivity for ethanol of 15.6 µA·mM−1·cm−2 with a linear range from 70 to 420 µM. A detection limit of 19 µM was obtained and negligible interferences from glucose, ascorbic acid, uric acid, and acetaminophen were observed.

A novel amperometric enzyme inhibition biosensor based on xanthine oxidase immobilised onto glassy carbon electrodes for bisphenol A determination

A novel and simple biosensor for the determination of bisphenol A (BPA) based on xanthine oxidase (XOD) enzymatic inhibition has been developed. The biosensor was prepared from xanthine oxidase immobilised by crosslinking with glutaraldehyde, with hypoxanthine as enzyme substrate, and was successfully applied to the determination of BPA using fixed potential amperometry. Biosensor performance was optimised with respect to the applied potential, influence of pH of the electrolyte solution, XOD loading and the substrate concentration. The enzyme inhibition mechanism was evaluated from Cornish-Bowden plus Dixon plots and was found to be reversible and competitive with an apparent inhibition constant of 8.15 nM. Under optimised conditions, the determination of BPA can be achieved in the linear range up to 41 nM with a detection limit of 1.0 nM, which is equal to the lowest reported in the literature, with very good repeatability and reproducibility. The selectivity of the biosensor was evaluated by performing an interference study and found to be excellent; and stability was investigated. It was successfully applied to the detection of BPA in mineral water and in river water.