Electrochemical behaviors of nicotine and its interaction with DNA

A Novel Electrochemical Sensor for Detection of Nicotine in Tobacco Products Based on Graphene Oxide Nanosheets Conjugated with (1,2-Naphthoquinone-4-Sulphonic Acid) Modified Glassy Carbon Electrode

A simple electrochemical sensor for nicotine (NIC) detection was performed. The sensor based on a glassy carbon electrode (GCE) was modified by (1,2-naphthoquinone-4-sulphonic acid)(Nq) decorated by graphene oxide (GO) nanocomposite. The synthesized (GO) nanosheets were characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), transmission electron microscope (TEM), FT-IR, and UV-Visible Spectroscopy. The insertion of Nq with GO nanosheets on the surface of GCE displayed high electrocatalytic activity towards NIC compared to the bare GCE. NIC determination was performed under the optimum conditions using 0.10 M of Na2SO4 as a supporting electrolyte with pH 8.0 at a scan rate of 100 mV/s using both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). This electrochemical sensor showed an excellent result for NIC detection. The oxidation peak current increased linearly with a 6.5-245 µM of NIC with R2 = 0.9999. The limit of detection was 12.7 nM. The fabricated electrode provided satisfactory stability, reproducibility, and selectivity for NIC oxidation. The reliable GO/Nq/GCE sensor was successfully applied for detecting NIC in the tobacco product and a urine sample.

Levels of nicotine in Ethiopian tobacco leaves

Tobacco is a valuable cash crop. It is the most widely grown non-food crop in the world. Tobacco use is widespread due to its addictive nature of its main constituent nicotine. Therefore, the knowledge of nicotine level in tobacco is important to tobacco industry and in the area of toxicology to control its harmful effect on health. There is no report in the literature on nicotine level of Ethiopian raw (unprocessed) tobacco leaves. Hence, the objective of this study is to determine the levels of nicotine in the Ethiopian tobacco leaves. Samples were collected based on their leaves positions, species and place of cultivation from different regions of Ethiopia. These were Virginia type tobacco from Shewa Robit and Billate, Burley and Oriental types of tobacco from Awassa and native tobacco used as pipe smoking (Gaya) from Wollayita. The level of nicotine in four different varieties of Ethiopian tobacco leaves was determined using high performance liquid chromatography. The level of nicotine in the four different varieties of Ethiopian tobacco were Virginia tobacco (3.26 %), the native tobacco ‘Gaya’ (1.10 %), Burley tobacco (0.650 %), and Oriental tobacco leaves (≤0.0500 %). It was found that the nicotine level of Ethiopian Virginia tobacco leaves increases from bottom to top leaf (stalk) positions of the tobacco plant. It was also found that the nicotine level of Ethiopian tobacco leaves varies in different species and the nicotine level of the same tobacco species differ in different area of cultivation. In general, the level of nicotine in Ethiopian tobacco is comparable with that in the rest of the world.

Electrochemical sensors based on multi-walled nanotubes for investigating the damage and action of 6-mercaptopurine on double-stranded DNA

Clear damage to dsDNA caused by 6-MP was observed. The damage to adenine was more severe than to guanine.

Biosensor based on ds-DNA decorated chitosan modified multiwall carbon nanotubes for voltammetric biodetection of herbicide amitrole

The interaction of amitrole and salmon sperm ds-DNA was studied using UV-vis and differential pulse voltammetry (DPV) at both bare and DNA-modified electrodes. Amitrole showed an oxidation peak at 0.445 V at a bare pencil graphite electrode (PGE). When ds-DNA was added into the amitrole solution, the peak current of amitrole decreased and the peak potential underwent a shift. UV-vis spectra showed that the absorption intensity of the ds-DNA at 260 nm decreased with increasing amitrole concentration, proving the interaction between amitrole and the ds-DNA. The results also showed that amitrole could interact with the ds-DNA molecules via the intercalative binding mode. Finally, a pretreated pencil graphite electrode (PGE) modified with multiwall carbon nanotubes (MWCNTs) and chitosan (CHIT) decorated with the ds-DNA were tested in order to determine amitrole content in solution. Electrochemical oxidation of amitrole bonded on DNA/MWCNTs-CHIT/PGE was used to obtain an analytical signal. A linear dependence was observed to exist between the peak current and 0.025-2.4 ng mL(-1) amitrole with a detection limit of 0.017 ng mL(-1). The sensor showed a good selectivity and precision for the determination of amitrole. Finally, applicability of the biosensor was evaluated by measuring the analyte in soil and water samples with good selectivity.