Determination of amiloride using a ds-DNA-modified pencil graphite electrode based on guanine and adenine signals

Voltammetric Techniques for the Analysis of Drugs using Nanomaterials based Chemically Modified Electrodes

Background:

Electroanalytical techniques play a very important role in the areas of medicinal, clinical as well as pharmaceutical research. Amongst these techniques, the voltammetric methods for the determination of drugs using nanomaterials based chemically modified electrodes (CMEs) have received enormous attention in recent years. This is due to the sensitivity and selectivity they provide on qualitative as well as quantitative aspects of the electroactive analyte under study. The aim of the present review was to discuss the work on nanomaterials based CMEs for the analysis of drugs covering the period from 2000 to present employing various voltammetric techniques for different classes of the drugs.

Methods:

The present review deals with the determination of different classes of drugs including analgesics, anthelmentic, anti-TB, cardiovascular, antipsychotics and anti-allergic, antibiotic and gastrointestinal drugs. Also, a special section is devoted for enantioanalysis of certain chiral drugs using voltammetry. The detailed information of the voltammetric determination for the drugs from each class employing various techniques such as differential pulse voltammetry, cyclic voltammetry, linear sweep voltammetry, square wave voltammetry, stripping voltammetry, etc. are presented in tabular form below the description of each class in the review.

Results:

Various nanomaterials including carbon nanotubes, graphene, carbon nanofibers, quantum dots, metal/metal oxide nanoparticles, polymer based nanocomposites have been used by researchers for the development of CMEs over a period of time. The large surface area to volume ratio, high conductivity, electrocatalytic activity and biocompatibility make them ideal modifiers where they produce synergistic effect which helps in trace level determination of pharmaceutical, biomedical and medicinal compounds. In addition, macrocyclic compounds as chiral selectors have been used for the determination of enantiomeric drugs where one of the isomers captured in the cavities of chiral selector shows stronger binding interaction for one of the enantiomorphs.

Conclusion:

arious kinds of functional nanocomposites have led to the manipulation of peak potential due to drug - nanoparticles interaction at the modified electrode surface. This has facilitated the simultaneous determination of drugs with almost similar peak potentials. Also, it leads to the enhancement in voltammetric response of the analytes. It is expected that such modified electrodes can be easily miniaturized and used as portable, wearable and user friendly devices. This will pave a way for in-vivo onsite real monitoring of single as well as multi component pharmaceutical compounds.

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.

Highly selective electrochemical biosensor for the determination of folic acid based on DNA modified-pencil graphite electrode using response surface methodology

An electrochemical DNA biosensor was proposed as a screening device for the rapid analysis of folic acid using a pencil graphite electrode modified with salmon sperm ds-DNA. At first, immobilization of the ds-DNA on pencil graphite electrode was optimized using response surface methodology. Solution pH, DNA concentration, time of DNA deposition and potential of deposition was optimized each at three levels. The optimum combinations for the reaction were pH 4.8, DNA concentration of 24 μg mL(-1), deposition time of 304 s, and deposition potential of 0.60 V, by which the adenine signal was recorded as 3.04 μA. Secondly the binding of folic acid to DNA immobilized on a pencil graphite electrode was measured through the variation of the electrochemical signal of adenine. Folic acid could be measure in the range of 0.1-10.0 μmol L(-1) with a detection limit of 1.06×10(-8) μmol L(-1). The relative standard deviations for ten replicate differential pulse voltammetric measurements of 2.0 and 5.0 μmol L(-1) folic acid were 4.6% and 4.3%, respectively. The biosensor was successfully used to measure folic acid in different real samples.

A sensitive and selective voltammetric sensor based on multiwall carbon nanotubes decorated with MgCr₂O₄ for the determination of azithromycin

In this report, we synthesized MgCr(2)O(4) nanoparticles and then multiwall carbon nanotubes were decorated with the MgCr(2)O(4) nanoparticles. The characteristics of the new materials were studied with different techniques such as transmission electron microscopy, Fourier transform infrared spectroscopy, atomic force microscopy and electrochemical impedance spectroscopy. The multiwall carbon nanotubes decorated with MgCr(2)O(4) nanoparticles were used as a new mediator for voltammetric determination of azithromycin. The oxidation peak of azithromycin was appeared at a potential of about 720 mV at a surface of the modified electrode. Differential pulse voltammetry exhibited two wide linear dynamic ranges of 0.25-4.0 and 4.0-10.0 μmol L(-1) azithromycin with a detection limit of 0.07 μmol L(-1) at pH 7.0. The influence of potential interfering compounds on the selectivity was studied. Finally, the modified electrode showed good sensitivity, selectivity and stability for the determination of azithromycin in real samples.

A novel sensitive DNA-biosensor for detection of a carcinogen, Sudan II, using electrochemically treated pencil graphite electrode by voltammetric methods

A simple and inexpensive methodology was used to develop a novel electrochemical sensor for the determination of Sudan II. The interaction of Sudan II with salmon sperm ds-DNA on the surface of salmon sperm ds-DNA-modified pencil graphite electrode (PGE) and in solution phase was studied, using differential pulse voltammetry. The difference between adenine and guanine signals of the ds-DNA after and before interaction with Sudan II was directly proportional to Sudan II concentration, which used for quantitative inspections. Using PGE, a linear calibration curve (R(2)=0.9958) was observed with 0.5-6.0 μg mL(-1) Sudan II. Furthermore, the LOD of 0.4 μg mL(-1) and linear range between 0.5 and 4.0 μg mL(-1) were achieved in solution phase. In the second part, Sudan II was determined on a pretreated pencil graphite electrode by means of adsorptive stripping differential pulse voltammetry. The peak current was linearly dependent on Sudan II concentration over the range of 0.0015-0.30 μg mL(-1), with a detection limit of 0.00007 μg mL(-1) Sudan II. Both ds-DNA-modified PGE and PPGE were applied to analyze Sudan II in real samples.