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The aim of this research was the determination of a microRNA (miRNA) using a DNA electrochemical aptasensor. In this biosensor, the complementary complementary DNA (cDNA) of miRNA-145 (a sense RNA transcript) was the target strand and the cDNA of miRNA-145 was the probe strand. Both cDNAs can be the product of the reverse transcriptase-polymerase chain reaction of miRNA. The proposed aptasensor's function was based on the hybridization of target strands with probes immobilized on the surface of a working electrode and the subsequent intercalation of doxorubicin (DOX) molecules functioning as the electroactive indicators of any double strands that formed. Electrochemical transduction was performed by measuring the cathodic current resulting from the electrochemical reduction of the intercalated molecules at the electrode surface. In the experiment, because many DOX molecules accumulated on each target strand on the electrode surface, amplification was inherently easy, without a need for enzymatic or complicated amplification strategies. The proposed aptasensor also had the excellent ability to regenerate as a result of the melting of the DNA duplex. Moreover, the use of DNA probe strands obviated the challenges of working with an RNA probe, such as sensitivity to RNase enzyme. In addition to the linear relationship between the electrochemical signal and the concentration of the target strands that ranged from 2.0 to 80.0 nM with an LOD of 0.27 nM, the proposed biosensor was clearly capable of distinguishing between complementary (target strand) and noncomplementary sequences. The presented biosensor was successfully applied for the quantification of DNA strands corresponding to miRNA-145 in human serum samples. [ABSTRACT FROM AUTHOR]

A novel conductive polymeric ionic liquid (IL)-Fe3O4 nanocomposite (represented as PIL-Fe3O4) based on inorganic-organic hybrid material was synthesized using two different methods. Nuclear magnetic resonance, Fourier transform infrared, X-ray diffraction, and field emission scanning electron microscopy characterized the structures of IL, Fe3O4 nanoparticles, and PIL-Fe3O4. The electrochemical sensors based on PIL-Fe3O4-modified glassy carbon electrode were fabricated, and each of these nanocomposites was examined for the ability to determine amlodipine besylate (AMD). The electrochemical study of the modified electrodes, as well as its efficiency for the electro-oxidation of AMD, was described in 0.1 M phosphate-buffered solution (pH 7.0) using voltammetric methods. The results exhibit a linear dynamic range from 1 to 500 nM and a detection limit of 0.36 nM. Finally, the modified electrode was used for the determination of AMD in pharmaceutical and biological samples. [ABSTRACT FROM AUTHOR]

The article discusses a displacement-dispersive liquid-liquid microextraction method based on the solidification of floating organic drop developed for separation and preconcentration of palladium (Pd) in road dust and aqueous samples. The authors say the method involves two steps of dispersive liquid-liquid microextraction based on solidification. The researchers say several factors that influence the extraction efficiency of Pd and its subsequent determination are optimized.

Describes the flame atomic absorption spectrometric determination of trace amounts of nickel after extraction and preconcentration onto natural modified analcime zeolite loaded with 2-(5-bromo-2-pyridylazo)-5-diethylaminophenol. Serious health problems that can result from inhalation of nickel and its compounds; Detection limit and calibration curve for analyte concentrations in the range of 0.1-8 microgram/milliliter final solution; Evaluation of the accuracy of the proposed method.

This paper presents an easy, fast, low cost, and sensitive approach for the electrochemical determination of quercetin based on its intercalation into DNA double helix. Electrochemical studies of the interaction between quercetin and DNA showed a decrease in peak currents with a reduction in redox reversibility of quercetin in the presence of the DNA. The electrochemical behavior of quercetin at a chitosan-entrapped carbon nanotube paste electrode coated with DNA was studied. A considerable increase was observed in the oxidation signal of quercetin at the DNA-coated electrode compared with a DNA-free electrode, indicating the preconcentration of quercetin due to its interaction with the surface-confined DNA layer. After optimizing the main experimental parameters influencing the biosensor response, its performance was evaluated from an analytical point of view. Two linear dependences of the anodic peak current of quercetin on its concentration were observed in the ranges of 0.40-7.50 and 7.50-30.0 µmol/L, with LOD and LOQ of 0.039 and 0.13 µmol/L, respectively. The proposed biosensor was successfully applied to the analysis of black and green tea extracts for their quercetin content. [ABSTRACT FROM AUTHOR]

A novel conductive polymeric ionic liquid (IL)-Fe3O4 nanocomposite (represented as PIL-Fe3O4) based on inorganic-organic hybrid material was synthesized using two different methods. Nuclear magnetic resonance, Fourier transform infrared, X-ray diffraction, and field emission scanning electron microscopy characterized the structures of IL, Fe3O4 nanoparticles, and PIL-Fe3O4. The electrochemical sensors based on PIL-Fe3O4-modified glassy carbon electrode were fabricated, and each of these nanocomposites was examined for the ability to determine amlodipine besylate (AMD). The electrochemical study of the modified electrodes, as well as its efficiency for the electro-oxidation of AMD, was described in 0.1 M phosphate-buffered solution (pH 7.0) using voltammetric methods. The results exhibit a linear dynamic range from 1 to 500 nM and a detection limit of 0.36 nM. Finally, the modified electrode was used for the determination of AMD in pharmaceutical and biological samples.

Dispersive liquid-liquid microextraction (DLLME) based on a task-specific ionic liquid (TSIL) was developed for the extraction and preconcentration of trace amounts of cadmium from aqueous samples, followed by flame atomic absorption spectrometry (FAAS) determination. In the proposed approach, cadmium ions are extracted from aqueous samples using small volumes of trioctylmethylammonium thiosalicylate (TOMATS) dissolved in acetone. TOMATS is a thiol-containing TSIL that can form metal thiolate complexes due to the chelating effect of the ortho-positioned carboxylate group relative to the thiol functionality. The main parameters affecting the performance of DLLME based on TSIL, such as pH, amount of TOMATS, extraction time, injection volume, salt addition, and centrifugation time, were optimized. Under optimum conditions, an LOD of 1.16 ng/mL and a good RSD of 1.8% at 60.0 ng/mL were obtained (n=7). The proposed method was applied to tap water, wastewater, well water, and milk samples. The results showed that DLLME based on TSIL combined with FAAS is a rapid, simple, sensitive, selective, low cost, volatile organic solvent-free, and efficient analytical method for the separation and determination of trace amounts of cadmium ions.

A simple and sensitive flame atomic absorption spectrometry technique was developed for the determination of trace amounts of cobalt (Co) in various samples after adsorption on modified analcime using a recently synthesized tetradentate Schiff base ligand, bis-(2-hydroxy-1-naphthaldimine)-N-diethylene-triamine, by a column method in the pH range of 5 to 7, with a flow rate of 1 mL/min. The influence of flow rates of the stripping and sample solution, the amount of ligand, types of stripping, and the least amount of eluent required for elution of the Co ion from the column were investigated. The effects of interfering ions on the recovery of Co were studied. The method was successfully applied for determination of Co in water and plant samples. The maximum capacity of the modified sorbent was found to be 0.58 mg/g of Co(II); the preconcentration factor was 250. Linearity was maintained at 0.2-40 microg/L in the original solution. The LOD was 1.44 x 10(-2) microg/L in the original solution.

The application of organo nanoclay 1-(2-pyridylazo)-2-naphthol (PAN)-immobilized as a new, easily prepared, and stable solid sorbent for preconcentration of trace amounts of Cu2+, Ni2+, and Mn2+ ions in aqueous solution is presented. The organo nanoclay was prepared by adding tetradecyldimethylbenzylammonium chloride onto montmorillonite and then saturating with PAN. A simple, rapid, selective, sensitive, and economical method was developed for the simultaneous separation of trace amounts of copper, nickel, and manganese in aqueous medium using PAN as an analytical reagent. The sorption was quantitative in the pH range of 6-9.5, and quantitative desorption occurred instantaneously with 5.0 mL 3 M HNO3. Linearity was maintained at 0.26-37 ng/mL for copper, 1-52 nglmL for nickel, and 0.2-21 ng/mL for manganese in the original solution. The detection limits were 0.04 ng/mL for Cu(II), 0.15 ng/mL for Ni(II), and 0.03 ng/mL for Mn(II) in the original solution (2delta(bl); delta = standard deviation and bl = blank). Various parameters, such as the effect of pH, breakthrough volume, and interference of a large number of anions and cations, have been studied, and the proposed method was used to determine these metal ions in water and standard samples. Determination of these metal ions in standard samples showed that the proposed method has good accuracy.

A simple, selective, reliable, and sensitive method for the determination of trace amounts of CU2+ ions in aqueous samples is proposed. The Cu2+ ions are adsorbed quantitatively during the passage of aqueous samples through an octadecyl (C18) silica membrane disk modified by a symmetrical tetradentate Schiff base ligand, N,N'-bis(4-phenylazo salicylaldimine) 3-chloro-1,2-phenylenediamine (H2L). The retained Cu2+ ions were then stripped from the disk by elution with the minimal amount of nitric acid solution and determined by flame atomic absorption spectrometry. Various parameters, such as the effect of pH, flow rate, type and amount of eluent, and the effects of various cationic interferences on the recovery of ions were studied. The proposed method permitted large enrichment factors (about 550 and higher). The limit of detection of the method was 1.5 x 10(-2) microg/L. The use of the same disk modified with 6 mg H2L for at least 30 times showed no change in the recovery of Cu2+ ions. The accuracy of the method was confirmed by determination of Cu2+ ions in standard samples [National Institute of Environmental Studies (NIES) No. 2 and Nippon Keikinzoku Kogyo (NKK) No. 920]. The results demonstrated good agreement with certified values.