Fabrication and Characterization of DNA Sensors from Metal Oxides Nanoparticles and Chitosan-Modified Glassy Carbon Electrodes

Voltammetric studies of a sensitive electrochemical deoxyribonucleic acid (DNA) sensor based on nano particles and multi-walled carbon nanotube (MWCNTs) for DNA immobilization is described. In this study, two nanoparticles were used, zirconium oxide (ZrO2) and titanium oxide (TiO2). Layer deposition technique was used to prepare nanoparticles/MWCNTs/chitosan (CHIT)-modified glassy carbon electrode (GCE) and DNA were immobilized to the GCE. The immobilization of DNA on the electrode was monitored by cyclic voltammetry (CV) analysis by measuring the change of peak currents using electroactive methylene blue (MB) as an indicator. Compared with previous DNA sensor with DNA directly incorporated on carbon electrodes, this carbon nanotube-based assay with its large surface area and good charge-transport characteristics increased DNA attachment quantity. Parameters used on this study including electrochemical characterization, scan rate study and pH optimization as well as chronoamperometry (CA) and chronocoulometry (CC). The electrochemical reduction and oxidation of the redox couples of MB (as a DNA indicator) can be recognized easily by the solid-phase voltammetry of nanoparticles. The cyclic voltammograms for the three differently modified electrodes, nanoparticles/CHIT, MWCNTs/CHIT and nanoparticles/MWCNTs/CHIT, showed that there are 2 major peaks due to the redox couple of MB. Electrochemical characterization of the two modified electrodes, nanoparticles/MWCNTs/CHIT, shows that both of this modified electrode give highest peak current, evident that the composite mixtures cause the increase in the redox peak current of MB. For hybridization study, the current enhancement observed in three differently fabricated DNA sensor based on DNA/TiO2/CHIT/GCE, DNA/MWCNTs/CHIT/GCE and DNA/TiO2/MWCNTs/CHIT/GCE, responding to redox couple of MB are compared. The sensor DNA/TiO2/MWCNTs/CHIT/GCE was found to the most be sensitive towards hybridized DNA. Parameters, used in this study include hybridization time, hybridization temperature, accumulation time, effect of varying concentration of probe, calibration curve, selectivity of DNA sensor, reproducibility and repeatability. From the studies, the optimized condition of hybridization for target ssDNA reaching the ssDNA probe is 30 min at 30 oC. The accumulation time of MB, time taken for MB to bind with dsDNA is 150 seconds, while, 100 μM of ssDNA probe was found to be the appropriate dosage for the fabrication of the senso

Voltammetric studies of nano zirconium dioxide/carbon nanotubes/chitosan-modified glassy carbon electrodes.

Voltammetric studies of a sensitive electrochemical DNA sensor based on ZrO2 nanoparticles and multi-walled carbon nanotube (MWNTs) for DNA immobilization is described. Layer deposition technique was used to prepare nano ZrO2/MWNTs/chitosan-modified glassy carbon electrode (GCE) and oligonucleotides were immobilized to the GCE. The immobilization of DNA on the electrode was monitored by cyclic voltammetry (CV) analysis by measuring the change of peak currents using electroactive methylene blue (MB) as an indicator. Compared with previous DNA sensor with oligonucleotides directly incorporated on carbon electrodes, this carbon nanotubes-based assay with its large surface area and good charge-transport characteristics increased DNA attachment quantity. Parameters used on this study including electrochemical characterization, scan rate study, pH optimization, and scanning electron microscope (SEM) as well as chronoamperometry (CA) and chronocoulometry (CC). The electrochemical reduction and oxidation of the redox couples of methylene blue (as a DNA indicator) can be recognized easily by the solid-phase voltammetry of microparticles. The cyclic voltammograms for three differently modified electrodes, nano ZrO2/chitosan, MWNTs/chitosan and nano ZrO2/MWNTs/chitosan, showed 2 major peaks responding to redox couple of methylene blue. INTRODUCTIO

Synthesis and characterization of molecularly imprinted polymer membrane for the removal of 2,4-dinitrophenol.

Molecularly imprinted polymers (MIPs) were prepared by bulk polymerization in acetonitrile using 2,4-dinitrophenol, acrylamide, ethylene glycol dimethacrylate, and benzoyl peroxide, as the template, functional monomer, cross-linker, and initiator, respectively. The MIP membrane was prepared by hybridization of MIP particles with cellulose acetate (CA) and polystyrene (PS) after being ground and sieved. The prepared MIP membrane was characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. The parameters studied for the removal of 2,4-dinitrophenol included the effect of pH, sorption kinetics, and the selectivity of the MIP membrane. Maximum sorption of 2,4-nitrophenol by the fabricated CA membrane with MIP (CA-MIP) and the PS membrane with MIP (PS-MIP) was observed at pH 7.0 and pH 5.0, respectively. The sorption of 2,4-dinitrophenol by CA-MIP and PS-MIP followed a pseudo-second-order kinetic model. For a selectivity study, 2,4-dichlorophenol, 3-chlorophenol, and phenol were selected as potential interferences. The sorption capability of CA-MIP and PS-MIP towards 2,4-dinitrophenol was observed to be higher than that of 2,4-dichlorophenol, 3-chlorophenol, or phenol

Electrochemical oxidation of ascorbic acid mediated by carbon nanotubes /Li+/ carbon paste modified solid electrode.

Multi-walled carbon nanotube (MWCNT) was used to modify BPPG electrode because of its unique structure and extraordinary properties. MWCNT modified electrode exhibited obvious enhancing and electrocatalyzing effects to the oxidation of ascorbic acid using cyclic voltammetry technique. MWCNT was bonded on BPPG electrode surface using carbon paste with ratio of 30% (w/w) carbon paste (binder): 70% (w/w) MWCNT. This method of modification has lowered the capacitance background current and enabled lower detection limit of ascorbic acid concentration. The electrical conductivity property of MWCNT modified electrode was further improved with the intercalation with lithium ion and resulted in current enhancement of 2 times on the oxidation current of ascorbic acid.Parameters of pH and temperature showed significant relation to the sensitivity of MWCNT modified electrode. Under the optimized parameters, the calibration curve constructed was linear up from 50 µM to 5 mM with sensitivity of 34.5 mA M-1. The practical application of MWCNT modified electrode was demonstrated with Vitamin C pill and orange juice. Good reproducibility and recovery of ascorbic acid concentration showed the feasibility of MWCNT modified electrode to be used in the detection of ascorbic acid in aqueous solution. This also proposed MWCNT modified BPPG electrode possessed advantages such as low detection limit, high stability, low cost and simplicity in fabrication