Voltammetric sensor based on electrodeposited molecularly imprinted chitosan film on BDD electrodes for catechol detection in buffer and in wine samples.

Phenolic compounds such as catechol are present in a wide variety of foods and beverages; they are of great importance due to their antioxidant properties. Their consumption protects against the development of certain diseases such as cancer and cardiovascular diseases. A MIP chitosan (CS) film has been electrodeposited on a boron doped diamond (BDD) electrode, by chronoamperommetry in the presence of catechol, followed by elution with 0.1 M KCl. The morphology of the MIP and non-MIP (NIP) film has been studied by AFM. The electrochemical response of the sensor analyzed by cyclic voltammetry (CV) indicates that the sensor shows excellent reproducibility (RSD = 4.1%) and repeatability (RSD = 7.0%) for catechol detection in the range of 0 to 80 µM, with a detection limit of 6.9 × 10-7 M and high selectivity to catechol recognition versus different phenolic compounds. The results obtained in a red wine show that it can detect catechol in a complex matrix.

Voltammetric Sensor Based on Molecularly Imprinted Chitosan-Carbon Nanotubes Decorated with Gold Nanoparticles Nanocomposite Deposited on Boron-Doped Diamond Electrodes for Catechol Detection.

Phenolic compounds such as catechol are present in a wide variety of foods and beverages; they are of great importance due to their antioxidant properties. This research presents the development of a sensitive and biocompatible molecular imprinted sensor for the electrochemical detection of catechol, based on natural biopolymer-electroactive nanocomposites. Gold nanoparticle (AuNP)-decorated multiwalled carbon nanotubes (MWCNT) have been encapsulated in a polymeric chitosan (CS) matrix. This chitosan nanocomposite has been used to develop a molecular imprinted polymers (MIP) in the presence of catechol on a boron-doped diamond (BDD) electrode. The structure of the decorated MWCNT has been studied by TEM, whereas the characterization of the sensor surface has been imaged by AFM, demonstrating the satisfactory adsorption of the film and the adequate coverage of the decorated carbon nanotubes on the electrode surface. The electrochemical response of the sensor has been analyzed by cyclic voltammetry (CV) where excellent reproducibility and repeatability to catechol detection in the range of 0 to 1 mM has been found, with a detection limit of 3.7 × 10-5 M. Finally, the developed sensor was used to detect catechol in a real wine sample.

Electroanalytical Performance of Nitrogen-Doped Graphene Films Processed in One Step by Pulsed Laser Deposition Directly Coupled with Thermal Annealing.

Graphene-based materials are widely studied to enable significant improvements in electroanalytical devices requiring new generations of robust, sensitive and low-cost electrodes. In this paper, we present a direct one-step route to synthetize a functional nitrogen-doped graphene film onto a Ni-covered silicon electrode substrate heated at high temperature, by pulsed laser deposition of carbon in the presence of a surrounding nitrogen atmosphere, with no post-deposition transfer of the film. With the ferrocene methanol system, the functionalized electrode exhibits excellent reversibility, close to the theoretical value of 59 mV, and very high sensitivity to hydrogen peroxide oxidation. Our electroanalytical results were correlated with the composition and nanoarchitecture of the N-doped graphene film containing 1.75 at % of nitrogen and identified as a few-layer defected and textured graphene film containing a balanced mixture of graphitic-N and pyrrolic-N chemical functions. The absence of nitrogen dopant in the graphene film considerably degraded some electroanalytical performances. Heat treatment extended beyond the high temperature graphene synthesis did not significantly improve any of the performances. This work contributes to a better understanding of the electrochemical mechanisms of doped graphene-based electrodes obtained by a direct and controlled synthesis process.

Highly Sensitive Voltammetric Glucose Biosensor Based on Glucose Oxidase Encapsulated in a Chitosan/Kappa-Carrageenan/Gold Nanoparticle Bionanocomposite.

In this work, an enzymatic sensor, based on a bionanocomposite film consisting of a polyelectrolyte complex (PEC) (Chitosan/kappa-carrageenan) doped with gold nanoparticles (AuNPs) encapsulating glucose oxidase (GOD) deposited on a gold electrode (Au) for glucose sensing, is described. Using the electrocatalytic synergy of AuNPs and GOD as a model of enzyme, the variation of the current (µA) as a function of the log of the glucose concentration (log [glucose]), shows three times higher sensitivity for the modified electrode (283.9) compared to that of the PEC/GOD modified electrode (93.7), with a detection limit of about 5 µM and a linearity range between 10 µM and 7 mM. The response of the PEC/AuNPs/GOD based biosensor also presents good reproducibility, stability, and negligible interfering effects from ascorbic acid, uric acid, urea, and creatinine. The applicability of the PEC/AuNPs/GOD based biosensor was tested in glucose-spiked saliva samples and acceptable recovery rates were obtained.

Voltammetric glucose biosensor based on glucose oxidase encapsulation in a chitosan-kappa-carrageenan polyelectrolyte complex.

In this work, a new design of voltammetric glucose biosensor, based on the encapsulation of glucose oxidase (GOx) in a chitosan/κ­carrageenan (CHIT/CAR) polyelectrolyte complex (PEC) using a simple coacervation process is presented. A conductometric monitoring of this is performed. Spectroscopic and morphological characterization of the PEC film encapsulating GOx is carried out. Compared to biosensors based on a chitosan film, a more sensitive voltammetric detection of glucose is obtained. Using square wave voltammetry (SWV), the CHIT/CAR PEC based biosensor exhibits a wide linearity range from 5 µM to 7 mM glucose with a detection limit of 5 µM. Excellent selectivity against ascorbic acid, uric acid and urea is observed and the applicability of the biosensor for glucose detection in spiked saliva samples was demonstrated.