Electrochemical interface based on polydopamine and gold nanoparticles/reduced graphene oxide for impedimetric detection of lung cancer cells.

The use of non-invasive approaches for monitoring therapy processes in cancer patients at late stages is truly needed. In this work, we aim to develop an electrochemical interface based on polydopamine combined with gold nanoparticles and reduced graphene oxide for impedimetric detection of lung cancer cells. Gold nanoparticles (around 75 nm) were dispersed onto reduced graphene oxide material pre-electrodeposited onto disposable fluorine doped tin oxide electrodes. The coordination between gold and carbonaceous material has somehow improved the mechanical stability of this electrochemical interface. Polydopamine was later introduced onto modified electrodes via self-polymerization of dopamine in an alkaline solution. The result has demonstrated the good adhesion and biocompatibility of polydopamine towards A-549 lung cancer cells. The presence of the two conductive materials (gold nanoparticles and reduced graphene oxide) has led to a six-times decrease in charge transfer resistance of polydopamine film. Finally, the as-prepared electrochemical interface was employed for impedimetric detection of A-549 cells. The detection limit was estimated to be only 2 cells per mL. These findings have proved the possibilities to use advanced electrochemical interfaces for point-of-care applications.

Sensing interface based on electrodeposited Cu-BTC microporous film for electrochemical detection of the painkiller paracetamol.

The use of metal-organic framework materials in electrochemical sensors has been gaining more attention in the last few years due to their highly porous structure and electrocatalytic activity. In this work, a novel paracetamol electrochemical sensor based on a Cu-BTC microporous film electrochemically grown onto glassy carbon electrode was introduced. The Cu-BTC film was deposited directly onto the electrode surface via an electrochemical approach using a Et3N probase to accelerate the growth of Cu-BTC. The fast growth enables the formation of a microporous structure with better adsorption of targeted molecules. The two-dimensional arrangement of units made of dimeric copper cations coordinated to carboxylate anions helped to improve the electrochemical conductivity and electron transfer rate at the electrode surface (charge transfer resistance was dramatically decreased from 2173 Ω to 86 Ω). The electrocatalytic activity of copper ion centers in Cu-BTC was studied with peak separation between oxidation and reduction peaks of pseudo-redox paracetamol molecules much shortened (from 629 mV to 87 mV). Consequently, the sensing parameters (sensitivity and detection limit) of the as-prepared paracetamol sensor were considerably improved. Further works need to be conducted on tailoring ligand structure in order to much improve the electrical conductivity of metal-organic frameworks for sensing purposes.

A novel bimetallic MOFs combined with gold nanoflakes in electrochemical sensor for measuring bisphenol A.

In this paper, a novel bimetallic Fe-Cu metal-organic framework combined with 1,3,5-benzenetricarboxylic acid (Fe-Cu-BTC) are synthesized using hydrothermal reaction. The bimetallic Fe-Cu-BTC with high BET (1504 cm3 g-1) and high Langmuir surface area (1831 cm3 g-1) is composited by gold nanoparticles to improve the conductivity and to develop their synergistic effect. A novel bisphenol A (BPA) sensor was prepared by dropcasting Fe-Cu-BTC on glassy carbon electrodes (GCE) followed by AuNPs electrodeposition. The Fe-Cu-BTC framework were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy studies (TEM), FT-IR, BET measurements and EDX spectra. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were carried out for surveying the electrochemical properties of the sensors and for the quantification of BPA. Two linear ranges of BPA concentrations 0.1-1.0 µM and 1.0-18 µM with 18 nM limit of detection were obtained. The developed sensor was used to measure the concentration of BPA in samples extracted from rain coat with the recovery ranging from 85.70 to 103.23%.

A novel electrochemical sensor based on double-walled carbon nanotubes and graphene hybrid thin film for arsenic(V) detection.

In this work, we demonstrate the preparation of hybrid thin films based on double-walled carbon nanotubes and graphene for electrochemical sensing applications. The hybrid films were synthesized on polycrystalline copper foil by thermal chemical vapor deposition under low pressure. This carbonaceous hybrid film has exhibited high transparency with a transmittance of 94.3 %. The occurrence of this hybrid material on the electrode surface of screen-printed electrodes was found to increase electroactive surface area by 1.4 times, whereas electrochemical current was enhanced by 2.4 times. Such a highly transparent and conductive hybrid film was utilized as a transducing platform of enzymatic electrochemical arsenic(V) sensor. The as-prepared sensor shows the linear detection of arsenic(V) in the range from 1 to 10 ppb, with a limit of detection as low as 0.287 ppb. These findings provide a promising approach to develop new multifunctional electrochemical sensing systems for environmental monitoring and biomedical diagnostics.