Amplification of urea detection based on pH-sensitive liposomes

BACKGROUND: This study aimed to develop an amplification method of urea detection based on pHsensitive liposomes. RESULTS: The urease covalently immobilized on the magnetic particles and the pH-sensitive liposomes encapsulating ferricyanide were added to the cyclic-voltammeter cell solution where urea was distributed. The conversion of urea into carbonic acid seemed to induce a pH decrease that caused a reduction in the electrostatic repulsion between the headgroups of weakly acidic 1,2-dipalmitoyl-sn-glycero3-succinate. The reduction induced the liposomes to release potassium ferricyanide that was encapsulated inside. The effects of urea concentration and pH value were investigated. A specific concentration (0.5 mg/mL) of the urea solution was set to observe the response. The activity of urease was reversible with respect to the pH change between 7 and 5. The sensitivity of this detection was almost identical to the comparable techniques such as an enzyme-linked immunosorbent assay and a field-effect transistor. CONCLUSIONS: In summary, the methodology developed in this study was feasible as a portable, rapid, and sensitive method.

Rapid detection of trace Hg~(2+) in animal matrix by specific DNA electrochemical sensor / 中国中药杂志

A highly specific electrochemical biosensor based on T-Hg~(2+)-T structure for fast screening trace Hg~(2+) in complex animal drug matrix was constructed by cyclic voltammetry(CV) and differential pulse voltammetry(DPV). In the presence of Hg~(2+), it can be specifically binded to the T base of DNA sequence on the surface of modified gold electrode, which changes the conformation of DNA molecule and the electrochemical signal. The concentration ratio of EDC/NHS, the concentration ratio of FC-DNA and the reaction time of the biosensor were optimized by the index of sensitivity and reproducibility in CV. The results showed that the stability of the biosensor was good within 3 days(RSD≤1.3%), the difference between batches was low(RSD=4.7%), and the specificity of the biosensor was high in the presence of interfering ions(As~(3+), Cd~(2+), Cu~(2+), Pb~(2+), Zn~(2+) and Fe~(3+)). DPV results showed that the peak current signal value has a linear relationship with the lgC_((Hg)) over a concentration range from 0.1 nmol·L~(-1) to 1.0 μmol·L~(-1) with a detection limit of 0.066 nmol·L~(-1). Finally, the recovery rate tested in the matrix of animal medicine was satisfactory as 99.17%-101.3%, which can meet the needs of the determination of trace Hg~(2+) in the matrix of Bombyx Batryticatus, and provide a new idea for the rapid screening of trace heavy metals in the matrix of other types of complex traditional Chinese medicine.

Determination of Phenol by an Electrochemical Method with Glassy Carbon Electrode / 中国药师

Objective: To establish an electrochemical method for the determination of phenol. Methods: An electrochemical workstation with three electrodes system was used with glassy carbon electrode as working electrode, Ag/AgCl as reference electrode and Pt as counter electrode. Cyclic voltammetry and differential pulse voltammetry were used for the determination of phenol. Results:Under the condition of 4% Na2SO4as the supporting electrolyte, phenol showed an obvious oxidation peak on the glassy carbon elec-trode. The peak current increased linearly with the concentration of phenol within the range of 0. 8 μg·ml-1-10. 2 μg·ml-1( r=0. 997 5). The lower limit of detection was 0. 20 μg·ml-1. The average recovery was 101. 2% (RSD=2. 2% , n=6). Conclusion:The method is simple and accurate, and can be used for the determination of phenol.

Electrochemical Construction of Vertical Single-Walled Carbon Nanotubes Array as Clenbuterol Sensor / 分析化学

Vertical single-walled carbon nanotubes (v-SWCNTs) array was constructed on glassy carbon electrode (GCE) by electrochemical method of electro-cyclic voltammetry (CV method).The synthesized electrode was very stable and was not easy to fall off.Via the amino groups of ethylenediamine (Ethylenediamine,EDA) and the carboxyl group of carboxylated carbon nanotubes,the SWCNTs were ordered to grow steadily on GCE(v-SWCNTs/EDA/GCE).The modified electrode was used to detect hydrochloric acid clenbuterol (CLE).The experimental results showed that the regular link of carbon nanotubes on GCE improved its utilization efficiency.The detection sensitivity of clenbuterol was 16.1 times higher than that of the bare GCE.Due to electron accelerating effect and nanometer effect of SWCNTs,the carboxyl peak current of SWCNTs was increased with the added CLE.The carboxyl peak current of SWCNTs had a good linear relationship with CLE concentration in the range of 10-120 ng/mL.The method was successfully applied to the determination of CLE in real urine samples with good recoveries.Also v-SWCNTs/EDA/GCE could be used as a new highly sensitive electrochemical sensor for CLE detection.

Preparation of Polydiallyl Dimethyl Ammonium Chloride Modified Reduced Graphene Oxide/Zinc Oxide Composite Materials and Its Application in Detection of Uric Acid / 分析化学

By using Zinc nitrate as precursor and hydraZine hydrate as reducing agent, polydiallyl dimethyl ammonium chloride modified reduced graphene oxide/Zinc oxide composite materials ( PDDA-rGO/ZnO) were prepared by simultaneous reduction of graphene oxide ( GO) and Zinc nitrate.The composite materials were characteriZed by Fourier transform infrared ( FTIR ) spectroscopy, X-ray diffractometer ( XRD ) and transmission electron microscopy ( TEM) , and their electrochemical catalytic activity for uric acid was studied by cyclic voltammetry ( CV ) and linear sweep voltammetry ( LSV ) measurements.The result showed that PDDA-rGO/ZnO modified glassy carbon electrode prepared here was sensitive, reproducible and stable, and had significant electrocatalytic activity for UA.When using linear sweep voltammetry for detection of UA, the responses of modified electrode were linear with UA concentration in the ranges of 0.02-0.1 mmol/L and 0.1-1.0 mmol/L respectively, with detection limit of 15.9 nmol/L (S/N=3).

DNA-binding studies of valrubicin as a chemotherapy drug using spectroscopy and electrochemical techniques / 药物分析学报

In this study, the molecular interactions between valrubicin, an anticancer drug, and fish sperm DNA have been studied in phosphate buffer solution (pH 7.4) using UV–Vis spectrophotometry and cyclic voltammetry techniques. Valrubicin intercalated into double stranded DNA under a weak displacement reaction with methylene blue (MB) molecule in a competitive reaction. The binding constant (kb) of valrubicin-DNA was determined as 1.75×103 L/mol by spectrophotometric titration. The value of non-electrostatic binding constant (kt0) was almost constant at different ionic strengths while the ratio of kt0/kb increased from 4.51% to 23.77%. These results indicate that valrubicin binds to ds-DNA via electrostatic and intercalation modes. Thermodynamic parameters including ΔH0, ΔS0 and ΔG0 for valrubicin-DNA interaction were determined as ?25.21×103 kJ/mol, 1.55×102 kJ/mol K and ?22.03 kJ/mol, respectively. Cyclic voltammetry study shows a pair of redox peaks for valrubicin at 0.45 V and 0.36 V (vs. Ag/AgCl). The peak currents decreased and peak positions shifted to positive direction in the presence of DNA, showing intercalation mechanism due to the variation in formal potential.

Electrooxidation of Methanol on Pt Modified with Adatoms (NI, CU, PB, CD).

The electro oxidation of methanol has been studied in alkaline medium NaOH 0.1 M and acid medium H2SO4 0.5 M on a platinum electrode and a platinum modified by adatom adsorption (Ni, Cu, Pb, and Cd). The influence of different experimental variables (methanol concentration, and temperature) is reported. Preliminary investigations by cyclic voltammetry showed that the catalytic activity of platinum is still too low to be considered as a practical catalyst. Underpotential deposition of lead, nickel, cadmium, or copper adatoms at platinum allowed increasing significantly the current densities.

A Wearable Wireless Electrochemical Instrument Used for In_vivo Neurotransmitter Detection / 分析化学

A wireless electrochemical recording device was designed for in_vivo neurotransmitters real_time detection. Low_power microcontroller MSP430 was chosen as main control unit in hardware system. Other modules were current detection module, waveform generator module and data transceiver module. This device had the merits of small size (2. 3 cm×1. 8 cm×0. 6 cm) and low power consumption. Firmware program design was based on uC/OS operating system. Combined with the PC software, the device could achieve online display and analysis of the recording data. For neurotransmitter detecting needs, the device implemented fast_scan cyclic voltammetry ( FSCV) and fixed_potential amperometry. By using fast_scan cyclic voltammetry method, a linear relationship ( R=0. 99 ) between the concentration of dopamine and response current was acquired in the range of 5. 0×10-7-7. 0×10-5 mol/L. In the in_vivo experiments, the electrically evoked dopamine was recorded in the caudate_putamen area of brain in rats. Experimental results showed that the system had high detection accuracy, which could realize qualitative and quantitative analysis of the brain neurotransmitter. This work would have a broad application prospect in the field of neuroscience research.

Electrochemical Characterizations of Quaternarized Nanodiamond-Myoglobin Modified Electrode / 分析化学

Through a series of chemical reactions, a kind of quaternary ammonium salt derivative of nanodiamond, ND-CO-NH-CH2-CH2-N ( CH3 ) 3+· I-( QAS-ND ) , was obtained , which was confirmed by FTIR, element analysis experiment and the electrochemistry measurements. Mixed myoglobin ( Mb) and QAS-ND solution was dropped on the surface of the glassy carbon ( GC ) electrode to prepare QAS-ND/Mb/GC modified electrode. In 0. 1 mol/L phosphate buffer solution (PBS) (pH 7. 0), Mb in the membrane exhibited direct electrochemical properties and showed good stability. The electrocatalytic property of the modified electrode toward H2 O2 was investigated, the results showed that the modified electrode could be used as the H2O2 biosensor to achieve fast, accurate detection of H2O2, with a detection limit of 3. 5 mmol/L (S/N=3).

Relationship Between Surface Morphology and Performance of a Spirally Hierarchical Structure-based Electrochemical Glucose Sensor / 分析化学

Zinc oxide nanowires were hydrothermally synthesized on the surface of an Au cylindrical spiral formed by manually spiraling an Au fiber around an optical fiber core, glucose oxidase was immobilized on these nanowires by physical adsorption, and then a spirally hierarchical structure-based glucose enzymatic electrode was obtained. The surface morphologies of the spirally hierarchical structures and corresponding enzymatic electrodes were extracted, and the electrochemical performances of the enzymatic electrodes were characterized. It was concluded that the synthesizing parameters of zinc oxide nanowires significantly affected the surface morphologies and glucose oxidase immobilization on the spirally hierarchical structures, and further the performances of related glucose sensors. With Zn2﹢concentration of the growth solution set at 25 mmol/L, the roughness of surface morphology was determined to be 0. 10 μm and correlation length 0. 29 μm, resulting in a better immobilization of glucose oxidase upon zinc oxide nanowires. In this case the sensitivity of the glucose sensor was determined to be 2. 15 μA/(mmol/L·cm2), the linear range was 0-4. 50 mmol/L, the low detection limit was 9. 20 μmol/L and Michaelis-Menten constant was 3. 68 mmol/L. The results not only benefit the batch production of the spirally hierarchical structure-based enzymatic electrodes, but also significantly improve the performances of the glucose sensors.

Study on Electrochemical Behaviors and Determination of Xanthine and Uric Acid on Modified Glassy Carbon Electrode / 分析化学

The silver doped poly ( L-lysine ) modified glassy carbon electrode was fabricated by cyclic voltammetry, the surface of the electrode was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. The electrochemical behaviors and the simultaneous detection of xanthine and uric acid were studied by cyclic voltammetry and differential pulse voltammetry. The results indicated that this modified electrode exhibited excellent electrocatalytic activity towards the oxidation of xanthine and uric acid. The stable oxidation peaks of xanthine and uric acid appeared with the peak potential of 0. 980V and 0. 600V respectively at the modified electrode in pH 3. 0 phosphate buffer solution. The oxidation peaks of xanthine and uric acid were separated at 380 mV. Under the optimum conditions, the linear ranges for the determination of xanthine and uric acid were 1 . 00 × 10-6-2 . 50 × 10-4 mol/L respectively by differential pulse voltammetry. The detection limits were 5. 0×10-7mol/L. The method has been applied to the simultaneous detection of xanthine and uric acid in healthy human urine with satisfactory results.

Spectral and electrochemical studies of fluvoxamine.

The spectral and voltammetric behavior of fluvoxamine (1) in aqueous buffers of varied pH is presented. Spectrophotometry, cyclic voltammetry, differential pulse polarography and coulometry were utilized to study its proton and electron transfer characteristics. Relevant thermodynamic and electrochemical data such as charge transfer coefficient (αna), heterogeneous forward rate constant (k0 f,h), etc, have been evaluated. An excellent electroanalytical assaying of 1 has been developed in differential pulse polarography at pH = 3. Molecular modeling on various acid-base conjugates of 1 and their several conformers has been carried out to arrive at the thermodynamic and conformational issues to correlate to the spectral and electrochemical observations.

Biocatalytic and electrochemical reduction of selected phenyl alkanones with antibacterial activity of the corresponding phenyl alkanols.

This paper reports the production of some phenyl alkanols by the biocatalytic and electrochemical reduction of selected Phenyl alkanones viz. Propiophenone, Butyrophenone, and Valerophenone. Baker‘s yeast was used in its free as well as immobilized form for biocatalytic reduction. Substrates showed the higher conversion rate when the cells were used in immobilized form. The electrochemical behavior of substrates was investigated cyclic voltammetrically to explore electrochemical reduction as alternative synthetic route for the preparation of alcohols. Results obtained from cyclic voltammetric studies were used for establishing optimum conditions for electrochemical reduction which was then carried out galvanostatically using economically viable stainless steel (SS-316) electrodes. The reduction products were isolated and purified by chromatographic techniques and characterized on the basis of spectral analysis. The products thus obtained also exhibited significant antibacterial activity against four strains of bacteria viz. Staphylococcus aureus, Enterococcus faecaulis, Escherichia coli, Pseudomonas aeruginosa.

Synthesis, characterization and biocidal studies of some aromatic alcohols.

The synthesis and characterization of aromatic alcohols such as 1-(4-bromo phenyl) ethanol, 1-(4-Hydroxy-3-methoxyphenyl) ethanol, (4-Hydroxy-3-methoxy-benzyl alcohol) employing biotransformation (using whole cells of Baker’s Yeast in their free as well as immobilized form in mixtures of glycerol and water) and Electrochemical technique are reported. The electrochemical behavior of 4-bromoacetophenone, 4-Hydroxy-3-methoxyacetophenone, and 4-Hydroxy-3- methoxybenzaldehyde was analyzed using cyclic voltammetry at glassy carbon electrode (GCE) and constant current electrolysis. Effect of scan rate and pH on the reduction peaks has been calculated. The kinetic parameters were also calculated and the process was found to be diffusion controlled. The products obtained were purified & then characterized by spectroscopic techniques. All the compounds have been tested in vitro against a number of microorganisms in order to assess their antimicrobial properties. Biocatalytic and Electrochemical procedures were found to be more effective, safe, economical, environmental friendly, easy to handle. These green methodologies over conventional chemical methods provide new and improved synthetic routes to many valuable compounds.

Eco friendly synthetic routes for the reduction of carbonyl and the substituted carbonyl compounds.

Incorporation of green methodology via biocatalytic and electrochemical steps using Baker’s Yeast and electrons as reducing agent respectively have been employed as a novel and efficient route to furnish relevent chiral building blocks for fine chemicals and pharmaceuticals. Reduction of selected ketones such as 2-methylcyclohexanone, 3-methylcyclohexanone, 4-methylcyclohexanone and ethyl-2-oxocyclopentanecarboxylate have been carried out by biotransformation (using whole cells of Baker’s Yeast in their free as well as immobilized form in mixtures of glycerol and water) and via electrochemical method to the corresponding alcohols. Optimum conditions for electrochemical reduction like solvent, supporting electrolyte, reduction potential and pH were determined at glassy carbon electrode employing cyclic voltammetric technique. The effect of scan rate, pH were also studied. The electrochemical reduction was carried out at constant current using stainless steel (SS-316) electrodes. The products obtained were purified & then the results of both reduction routes (biocatalytic & electrochemical) were compared and then characterized by spectroscopic techniques.