A label-free electrochemical biosensor based on tubulin immobilized on gold nanoparticle/glassy carbon electrode for the determination of vinblastine.

Vinblastine (VLB) is prescribed for a wide variety of cancers. Therefore, development of sensitive methods for early diagnosis is urgently required. In this work, a highly sensitive and label-free impedimetric biosensor was fabricated for the electrochemical detection of VLB. First, the gold nanoparticles (AuNPs) were electrodeposited on the surface of a glassy carbon electrode (GCE). 3-Mercaptopropionic acid (MPA) was self-assembled over the AuNPs. Then, tubulin (TUB), as a receptor, was covalently immobilized at the AuNPs/GCE surface via carbodiimide coupling reaction using N-(3 dimethylaminopropyl)-N'-ethyl carbodiimide (EDC) and N-hydroxy succinimide (NHS). The step-by-step modification process was characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in the presence of a redox probe [Fe(CN)6]3-/4-. The VLB concentration was measured through the increase of impedance values in the corresponding specific binding of VLB and TUB. The increased electron-transfer resistance (R et) values were proportional to the value of VLB concentrations in the range of 0.4 to 65.0 nmol L-1 with a detection limit of 8.4 × 10-2 nmol L-1 (SN-1 = 3). The practical analytical performance of the proposed method was demonstrated by determination of VLB in plant extracts and human serum samples with satisfactory recoveries.

Electrochemically oxidized multiwalled carbon nanotube/glassy carbon electrode as a probe for simultaneous determination of dopamine and doxorubicin in biological samples.

A facile and effective approach of fabricating oxidized multiwalled carbon nanotube/glassy carbon electrode (OMWCNT/GCE) is herein reported. The OMWCNT/GCE was prepared by electrochemical oxidation method in basic media (0.5 mol L(-1) NaOH solution) and used as a sensor for simultaneous determination of dopamine (DA) and doxorubicin (DOX). Scanning electron microscopy, energy dispersive X-ray spectroscopy and cyclic voltammetry were used for characterization and performance study of the OMWCNT/GCE. The modified electrode exhibited good electrocatalytic properties toward the oxidation of DA and DOX. Peaks potential difference of 240 mV between DA and DOX was large enough to determine DA and DOX individually and simultaneously. Square wave voltammetry (SWV) was used for the simultaneous determination of DA and DOX in their binary mixture. Under the optimum conditions, the linear concentration dependences of SW peak current responses were observed for DA and DOX in the concentration ranges of 0.03-55 µmol L(-1) and 0.04-90 µmol L(-1), respectively. The detection limits (S/N = 3) were 8.5 × 10(-3) µmol L(-1), and 9.4 × 10(-3) µmol L(-1) for DA and DOX, respectively. The analytical utility of OMWCNT/GCE was also successfully demonstrated for the simultaneous determination of DA and DOX in human blood serum and urine samples. Graphical Abstract Fabrication of new oxidized multiwalled carbon nanotube/glassy carbon electrode for simultaneous determination of dopamine and doxorubicin.

A novel electrochemical sensor based on magneto Au nanoparticles/carbon paste electrode for voltammetric determination of acetaminophen in real samples.

An electrochemical magneto Au nanoparticles/carbon paste electrodes (MAuNP/CPE) which is used for the determination of acetaminophen (AC) in real samples was developed. Initially, Au nanoparticles were immobilized at the surface of Fe3O4 (AuNPs@Fe3O4), which was used as a sorbent for capturing AC molecules. After adding AuNPs@Fe3O4 to the AC solution and stirring for 20 min, the AuNPs@Fe3O4 was gathered on the magneto electrode based on its magnetic field. The AC molecules which became adsorbed at AuNPs@Fe3O4 were analyzed by differential pulse voltammetry (DPV). For characterization and investigation of the performance of AuNPs@Fe3O4 and MAuNPs/CPE, various methods, including scanning electron microscopy, X-ray diffraction, UV-Vis spectroscopy, electrochemical impedance spectroscopy, cyclic voltammetry and DPV were used. Under the optimized conditions, the anodic peak current was linear to the concentration of AC in the range of 0.1 to 70.0µmol L(-1) with the detection limit of 4.5×10(-2)µmol L(-1). This method was also successfully used to detect the concentration of AC in pharmaceutical formulations and human serum samples. In addition, the proposed magneto sensor exhibited good reproducibility, long-term stability and fast current response.

Construction a magneto carbon paste electrode using synthesized molecularly imprinted magnetic nanospheres for selective and sensitive determination of mefenamic acid in some real samples.

A novel magneto multiwalled carbon nanotube/carbon paste electrode (MMW/CPE) for the determination of mefenamic acid (MFA) was introduced. Magnetic molecularly imprinted polymer nanoparticles (MMIPNPs) were synthesized and then added to the solution of MFA. After stirring for 20 min, the MMW/CPE was immersed in the solution of MFA (contain MMIPNPs) and the MMIPNPs were captured by it. Then oxidation of MFA was analyzed by differential pulse voltammetry (DPV). Electrochemical impedance spectroscopy, cyclic voltammetry, and DPV were employed to characterize the MMW/CPE. The MMIPNPs exhibited a high selectivity and sensitivity toward MFA. The effect of various experimental parameters including pH, MMIPNPs dosage, stirring time, accumulation potential and time on the voltammetric response of MFA were investigated. Under the optimal conditions, selective detection of MFA in a linear concentration range of 2.0-1000.0 nmol L(-1) was performed with the detection limit of 1.2 nmol L(-1) (3S/N). To further study the practical applicability of this method, it was applied to the analysis of some real samples and the obtained results were satisfactory.