Multilayer structured immunosensor based on a glassy carbon electrode modified with multi-wall carbon nanotubes, polythionine, and gold nanoparticles

An electrochemical immunosensor based on reduced graphene oxide/multiwalled carbon nanotubes/thionine/gold nanoparticle nanocomposites for the sensitive testing of follicle-stimulating hormone

Follicle-Stimulating Hormone (FSH) is a kind of gonadotropin which can promote human reproduction and development. Abnormal FSH levels may lead to endocrine disorders and infertility. Sensitive determination of FSH is very significant for the clinical diagnosis of these diseases. Here, an electrochemical immunosensor based on a screen-printed electrode (SPE) was developed for the detection of FSH. Nanocomposites, compounded with reduced graphene oxide (rGO), multiwalled carbon nanotubes (MWCNTs), thionine (Thi) and gold nanoparticles (AuNPs), were used for increasing the specific surface area to adsorb molecules and amplify signals. The rGO/MWCNTs/Thi/AuNP nanocomposites, anti-FSH and BSA were successively assembled onto a SPE to fabricate the immunosensor. Electrochemical performance of the modified immunosensor was studied by differential pulse voltammetry (DPV), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). FSH testing was based on the principle that the insulating FSH antigen-antibody immunocomplex could retard the electron transfer of Thi which led to the decrease of the DPV current response. Under optimum conditions, the rGO/MWCNTs/Thi/AuNP modified immunosensor exhibited high sensitivity and accuracy for the determination of FSH in a linear range from 1 mIU mL^-1 to 250 mIU mL^-1, and the detection limit was 0.05 mIU mL^-1 at a signal-to-noise ratio of 3. The immunosensor was successfully applied for the determination of quality serum samples with a recovery of 94.0-109.8%. The electrochemical immunosensor could be utilized for testing other gonadotropins.

Electrochemical sensors and biosensors based on redox polymer/carbon nanotube modified electrodes: a review

The aim of this review is to present the contributions to the development of electrochemical sensors and biosensors based on polyphenazine or polytriphenylmethane redox polymers together with carbon nanotubes (CNT) during recent years. Phenazine polymers have been widely used in analytical applications due to their inherent charge transport properties and electrocatalytic effects. At the same time, since the first report on a CNT-based sensor, their application in the electroanalytical chemistry field has demonstrated that the unique structure and properties of CNT are ideal for the design of electrochemical (bio)sensors. We describe here that the specific combination of phenazine/triphenylmethane polymers with CNT leads to an improved performance of the resulting sensing devices, because of their complementary electrical, electrochemical and mechanical properties, and also due to synergistic effects. The preparation of polymer/CNT modified electrodes will be presented together with their electrochemical and surface characterization, with emphasis on the contribution of each component on the overall properties of the modified electrodes. Their importance in analytical chemistry is demonstrated by the numerous applications based on polymer/CNT-driven electrocatalytic effects, and their analytical performance as (bio) sensors is discussed.

Asymmetric-based novel poly(ether-imide)s: Preparation, properties, kinetics of thermal decomposition, and study electrochemical oxidation behavior by using nanocomposite paste of polymer and multi-walled carbon nanotube

A series of novel fluorescent poly(ether-imide)s (PEIs) bearing ether linkage and diarylimidazole pendant in the backbone was successfully prepared by polycondensation reaction between a new unsymmetrical diamine and commercially available tetracarboxylic acid dianhydrides. The PEIs were characterized by Fourier transform infrared, 1H-NMR, UV-vis spectroscopy, fluorimetry, scanning electron microscopy and elemental analysis. The PEIs with inherent viscosities in the range of 0.47–0.63 dL g−1 showed excellent solubility in various aprotic solvents such as N-methylpyrrolidone, dimethyl sulfoxide, N, N-dimethylacetamide and N,N-dimethylformamide. Thermal properties of new PEIs were evaluated by differential scanning calorimetric and thermogravimetric analysis in N2 and air. These polymers showed glass transition temperatures ( Tg) in the range of 269–333 °C and 10% weight loss temperatures above 400 °C in air atmosphere. The data obtained from TGA experiments of these polymers have been applied in different kinetic equations such as Coats–Redfern, Kissinger and Criado methods, to determine the kinetic parameters ( E, ▵ S, ▵ G, ▵ H) and mechanism of thermal decomposition. Herein a method based on the adsorptive stripping cyclic voltammetry technique to investigate electrochemical oxidation of these polymers by using multi-walled carbon nano tubes modified glass electrode is also reported.