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A new hydrogen peroxide (HO) sensor is fabricated based on a multiwalled carbon nanotube-modified glassy carbon electrode (MWCNT-GCE) and reactive blue 19 (RB). The charge transfer coefficient, α, and the charge transfer rate constant, k, of RB adsorbed on MWCNT-GCE were calculated and found to be 0.44 ± 0.01 Hz and 1.9 ± 0.05 Hz, respectively. The catalysis of the electroreduction of HO by RB-MWCNT-GCE is described. The RB-MWCNT-GCE shows a dramatic increase in the peak current and a decrease in the overvoltage of HO electroreduction in comparison with that seen at an RB modified GCE, MWCNT modified GCE, and activated GCE. The kinetic parameters such as α and the heterogeneous rate constant, k', for the reduction of HO at RB-MWCNT-GCE surface were determined using cyclic voltammetry. The detection limit of 0.27μM and three linear calibration ranges were obtained for HO determination at the RB-MWCNT-GCE surface using an amperometry method. In addition, using the newly developed sensor, HO was determined in real samples with satisfactory results.

This study aims at designing a novel impedimetric aptasensor to determine carcinoembryonic antigen (CEA). The CEA aptasensor was developed by covalent immobilization of an amine-modified CEA aptamer on the surface of a glassy carbon electrode (GCE) which was modified by gold nanoparticles (AuNPs) incorporated in amino-functionalized MCM-41 (AMCM). After the aptamer was immobilized, CEA was incubated on the surface of an Ap-GA-AuNPs/AMCM-GCE. The change in the interfacial charge transfer resistance (R ct ) of the redox marker served as an excellent signal for the quantitative determination of CEA. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to display the aptamer immobilization on the electrode surface. Through the EIS method, the linear range and the detection limit of CEA were found to be 1.0 × 10 −3 −100.0 ng mL −1 and 9.8 × 10 −4 ng mL −1 respectively. Moreover, the proposed aptasensor was used to determine of CEA in patient and healthy human serum samples and the results indicated that this aptasensor has great potential for practical application which the strength point of this aptasensor.

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