Single-walled carbon nanotubes (SWCNT) modified disposable graphite electrodes (SWCNT-PGEs) were investigated in our study for the improved electrochemical monitoring of nucleic acids and biomolecular interactions based on the higher signal enhancement comparison to bare PGEs. The surface morphologies of bare PGE and SWCNT-PGE were firstly explored using scanning electron microscopy (SEM) analysis. The easy surface modification of disposable graphite electrodes with carbon nanotubes was performed by passive adsorption, and DNA was then immobilized onto the SWCNT-PGEs by the formation of covalent coupling between the carboxylated ends of nanotubes and the amine group in the guanine bases of DNA. The overall performance of SWCNT-PGEs has also been studied, and discussed in terms of optimum analytical conditions; such as, the effect of pretreatment step, CNT concentration, DNA concentration, etc. The reproducible detection of DNA represent a very attractive approach for the further detection of interaction between the anticancer drug, daunorubicin (DNR) and double stranded DNA (dsDNA). Voltammetric results were complemented with electrochemical impedance spectroscopy (EIS), that was used to characterize the successful construction of carbon nanotubes modification onto the surface of PGEs.

The application of multiwalled carbon nanotube (MWCNT) based screen printed graphite electrodes (SPEs) was explored in this study for the electrochemical monitoring of DNA hybridization related to specific sequences on Hepatitis B virus (HBV) DNA. After the microscopic characterization of bare MWCNT-SPEs and DNA immobilized ones was performed, the optimization of assay has been studied. The development of screen printing process combined with nanomaterial based disposable sensor technology leads herein a great opportunity for DNA detection using differential pulse voltammetry (DPV) by measuring the guanine oxidation signal observed at þ 1.00 V in the presence of DNA hybridization between HBV probe and its complementary, target. The detection limit estimated for signal to noise ratios ¼ 3 corresponds to 96.33 nM target concentration in the 40 mL samples. The advantages of carbon nanotube based screen printed electrode used for electrochemical monitoring of DNA hybridization are discussed with sensitivity, selectivity and reproducibility in comparison with previous nanomaterial based electrochemical transducers developed for DNA or other biomolecular recognitions.

Carboxylic acid functionalized single-walled carbon nanotubes modified graphite sensors (SWCNT-PGEs) were developed for electrochemical monitoring of direct DNA hybridization related to specific sequence of Hepatitis B virus, which substantially enhance the electrochemical transduction resulting from guanine oxidation signal comparison to bare PGEs. The performance characteristics of DNA hybridization on disposable CNT-PGE were explored measuring the guanine signal in terms of optimum analytical conditions; probe and target concentration, hybridization time, and selectivity. The voltammetric results were also complemented with electrochemical impedance spectroscopy (EIS), that was used to characterize the successful construction of carbon nanotubes modification onto the surface of PGEs.

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A magnetic particle assay has been designed herein that can report the interactions of DNA aptamers with their cognate protein targets lysozyme (LYS) and human thrombin (THR). Electrochemical sensing of the biomolecular recognition between each aptamer and its target was explored by using a disposable graphite electrode, PGE, in combination with differential pulse voltammetry (DPV). The magnitudes of the oxidation signals of LYS and THR were measured at þ 780 mV and þ 680 mV, respectively, after interaction with the cognate aptamers attached to the surface of magnetic particles. The detection limits estimated for signal to noise ratios above 3.0 correspond to the concentrations of 10.77 mg/mL LYS (769 nM) and 2.00 mg/mL THR (54.5 nM). Our aptamer based approach that combines magnetic particles with a disposable graphite electrode performs well compared to other aptamer-based sensor-formats for quantitative protein detection with respect to sensitivity, selectivity, detection limit, and reproducibility.