P. Gopal

A novel horseradish peroxidase biosensor towards the detection of dopamine: a voltammetric study.

A polymerized film of glycine (Gly) was prepared on the surface of carbon paste electrode (CPE) through the cyclic voltammetry (CV) technique. A novel biosensor for the determination of dopamine (DA) has been constructed based on horseradish peroxidase (HRP) and multiwalled carbon nanotubes (MWCNTs) immobilizing on Poly (Gly)/CPE through silica sol-gel (SiSG) entrapment. CV measurements were employed in order to understand the feasibility of poly (Gly) as an electron carrier between the immobilized peroxidase and the surface of CPE. By using differential pulse voltammetry (DPV) the calibration curves of DA was obtained in the range of 15-865 μM. The limit of detection (LOD) and limit of quantification (LOQ) of DA was found to be 6×10⁻⁷ M and 2×10⁻⁶ M respectively. The apparent Michaelis-Menten constant (Km(app)) was found to be 0.5 mM and illustrated that the good biological activity of the fixed enzyme. Electrochemical impedance spectroscopy (EIS) results confirmed the rapid electron transfer and also the immobilization of enzyme on the electrode surface. The biosensor showed high sensitivity, selectivity and reproducibility. This method has been used to determine DA in the presence of various interferences and in clinical preparations.

Electrochemical sensing of paracetamol and its simultaneous resolution in the presence of dopamine and folic acid at a multi-walled carbon nanotubes/poly(glycine) composite modified electrode

A facile and sensitive nanocomposite sensor was developed based on the electropolymerization of glycine (Gly) onto the surface of a glassy carbon electrode (GCE) using cyclic voltammetry (CV) followed by drop casting multi-walled carbon nanotubes (MWCNTs). The developed nanocomposite sensor (MWCNTs/poly(Gly)/GCE) was characterized using an electrochemical impedance spectroscopy (EIS) technique. The developed nanocomposite sensor offered high catalytic activity in sensing the paracetamol (PC) individually and simultaneously in the presence of dopamine (DA) and folic acid (FA). The limit of detection (LOD) and limit of quantification (LOQ) were found to be 5 × 10−7 M and 1.7 × 10−6 M respectively with a dynamic range from 5 × 10−7 to 1 × 10−5 M. The fabricated sensor showed good precision and accuracy with a relative standard deviation of 1.28%. The proposed composite sensor was successfully applied towards the determination of PC in human blood serum and pharmaceutical samples.

Electrocatalytic boost up of epinephrine and its simultaneous resolution in the presence of serotonin and folic acid at poly(serine)/multi-walled carbon nanotubes composite modified electrode: A voltammetric study.

The present paper describes the new strategy for the development of nanosensor based on dropcasting of multi-walled carbon nanotubes (MWCNTs) followed by electropolymerization of serine (ser) onto the glassy carbon electrode (GCE). The developed nanocomposite sensor was abbreviated as poly(ser)/MWCNTs/GCE and was characterized by using electrochemical impedance spectroscopy (EIS) technique. The EIS results confirmed the fast electron transfer rate at the surface of poly(ser)/MWCNTs/GCE. The proposed sensor exhibited good catalytic activity towards the sensing of epinephrine (EP) individually and simultaneously in the presence of serotonin (5-HT) and folic acid (FA) in 0.1M phosphate buffer solution (PBS) at pH7.0. The limit of detection (LOD) and limit of quantification (LOQ) of EP was found to be 6×10(-7)M and 2×10(-6)M respectively. The fabricated sensor showed excellent precision and accuracy with a relative standard deviation (RSD) of 4.86%. The proposed composite sensor was effectively applied towards the determination of EP in human blood serum and pharmaceutical injection sample.

Correction: Preparation, characterization and analytical application of an electrochemical laccase biosensor towards low level determination of isoprenaline in human serum samples

A novel electrochemical biosensor has been developed based on the immobilization of multiwalled carbon nanotubes (MWCNT) on to a glassy carbon electrode (GCE) and subsequent casting of silica sol–gel (SiSG) entrapped laccase (Lac) enzyme on to the MWCNT/GCE. The catalytic activity of laccase biosensor was found to be good enough for sensitive determination of isoprenaline (ISP) with the aid of voltammetric techniques and we have also demonstrated the detailed electrochemical redox mechanism of ISP. From the effect of the pH, we have optimized the optimum pH as 6.5, and from effect of scan rate we have evaluated the kinetic parameters, heterogeneous rate constant, charge transfer coefficient and diffusion coefficient values. Furthermore the limit of detection (LOD) and limit of quantification (LOQ) values were found to be 1.8 × 10−7 M and 6.0 × 10−7 M, respectively. The simultaneous determination of ISP in the presence of uric acid (UA) and ascorbic acid (AA) was successfully carried out. The surface nature of the biosensor was characterized by using electrochemical impedance spectroscopy. Finally the validation of the proposed method was verified by the recovery of injection (ISP) in serum samples and their recoveries were found to be in a satisfactory range. The proposed method was found to have good repeatability, reproducibility and stability with low relative standard deviation (RSD) values.

A Novel Electrochemical Sensor Based on Multi-walled Carbon Nanotubes/Poly (L-Methionine) for the Investigation of 5-Nitroindazole: A Voltammetric Study

Abstract A novel electrochemical sensor was fabricated by electro polymerization of L-Methionine on glassy carbon electrode (PLMT#GCE) followed by drop casting of multi-walled carbon nanotubes (MWCNTs) on PLMT#GCE to form an MWCNT@PLMT composite-modified GCE (MWCNT@ PLMT#GCE). The modified electrode exhibited considerable electrochemical activity towards the reduction of 5-nitroindazole (5-NI) in Britton-Robinson (BR) buffer solution of pH 8.0. From the concentration studies, the differential pulse voltammetry reveals that the limit of detection (LOD), limit of quantification (LOQ) and correlation coefficient (R) values for 5-NI as 6.1×10-6 mol/L, 1.7×10-5 mol/L and 0.997 respectively. The effects of scan rate, pH of buffer solution and concentration (low to high) of 5-NI was studied in detailed and its electrochemical reduction mechanism was proposed. The interfacial electron transfer behavior of 5-NI was studied by electrochemical impedance spectroscopy (EIS) and results showed that the charge transfer rate was enhanced at MWCNT@PLMT#GCE, when compared with PLMT#GCE, MWCNT@GCE and bare GCE. According to the results obtained, the MWCNT@PLMT#GCE can be used as a suitable, sensitive and high reproducible electrochemical sensor towards the electrochemical determination of 5-NI.