Potentiometric pH Nanosensor for Intracellular Measurements: Real-Time and Continuous Assessment of Local Gradients.

We present a pH nanosensor conceived for single intracellular measurements. The sensing architecture consisted of a two-electrode system evaluated in the potentiometric mode. We used solid-contact carbon nanopipette electrodes tailored to produce both the indicator (pH nanosensor) and reference electrodes.

Combined electrochemistry and mass spectrometry imaging to interrogate the mechanism of action of modafinil, a cognition-enhancing drug, at the cellular and sub-cellular level.

Modafinil is a mild psychostimulant-like drug enhancing wakefulness, improving attention and developing performance in various cognitive tasks, but its mechanism of action is not completely understood. This is the first combination of amperometry, electrochemical cytometry and mass spectrometry to interrogate the mechanism of action of a drug, here modafinil, at cellular and sub-cellular level. We employed single-cell amperometry (SCA) and intracellular vesicle impact electrochemical cytometry (IVIEC) to investigate the alterations in exocytotic release and vesicular catecholamine storage following modafinil treatment.

Intracellular injection of phospholipids directly alters exocytosis and the fraction of chemical release in chromaffin cells as measured by nano-electrochemistry.

Using a nano-injection method, we introduced phospholipids having different intrinsic geometries into single secretory cells and used single cell amperometry (SCA) and intracellular vesicle impact electrochemical cytometry (IVIEC) with nanotip electrodes to monitor the effects of intracellular incubation on the exocytosis process and vesicular storage. Combining tools, this work provides new information to understand the impact of intracellular membrane lipid engineering on exocytotic release, vesicular content and fraction of chemical release. We also assessed the effect of membrane lipid alteration on catecholamine storage of isolated vesicles by implementing another amperometric technique, vesicle impact electrochemical cytometry (VIEC), outside the cell.

Mass Spectrometry Imaging Shows Modafinil, A Student Study Drug, Changes the Lipid Composition of the Fly Brain.

Modafinil, a widely used psychoactive drug, has been shown to exert a positive impact on cognition and is used to treat sleep disorders and hyperactivity. Using time-of-flight secondary ion mass spectrometric imaging, we studied the changes of brain lipids of Drosophila melanogaster induced by modafinil to gain insight into the functional mechanism of modafinil in the brain. We found that upon modafinil treatment, the abundance of phosphatidylcholine and sphingomyelin species in the central brain of Drosophila is significantly decreased, whereas the levels of phosphatidylethanolamine and phosphatidylinositol in the brains show significant enhancement compared to the control flies.

Direct Measurement of Total Vesicular Catecholamine Content with Electrochemical Microwell Arrays.

We have designed and fabricated a microwell array chip (MWAC) to trap and detect the entire content of individual vesicles after disruption of the vesicular membrane by an applied electrical potential. To understand the mechanism of vesicle impact electrochemical cytometry (VIEC) in microwells, we simulated the rupture of the vesicles and subsequent diffusion of entrapped analytes. Two possibilities were tested: (i) the vesicle opens toward the electrode, and (ii) the vesicle opens away from the electrode.

Modified fractal iron oxide magnetic nanostructure: A novel and high performance platform for redox protein immobilization, direct electrochemistry and bioelectrocatalysis application.

A novel biosensing platform based on fractal-pattern of iron oxides magnetic nanostructures (FIOMNs) and mixed hemi/ad-micelle of sodium dodecyl sulfate (SDS) was designed for the magnetic immobilization of hemoglobin (Hb) at a screen printed carbon electrode (SPCE). The FIOMNs was successfully synthesized through hydrothermal approach and characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). In order to provide guidelines for the mixed hemi/ad-micelle formation, zeta-potential isotherms were investigated.

Mixed Hemi/Ad-Micelle Sodium Dodecyl Sulfate-Coated Magnetic Iron Oxide Nanoparticles for the Efficient Removal and Trace Determination of Rhodamine-B and Rhodamine-6G.

Mixed hemi/ad-micelle sodium dodecyl sulfate (SDS)-coated magnetic iron oxide nanoparticles (MHAMS-MIONPs) were used as an efficient adsorbent for both removal and preconcentration of two important carcinogenic xanthine dyes named rhodamine-B (RB) and rhodamine-6G (RG). To gain insight in the configuration of SDS molecules on the surface of MIONPs, zeta potential measurements were performed in different [SDS]/[MIONP] ratios. Zeta potential data indicated that mixed hemi/ad-micelle MHAM was formed in [SDS]/[MIONP] ratios over the range of 1.

Optimization of magnetic stirring assisted dispersive liquid-liquid microextraction of rhodamine B and rhodamine 6G by response surface methodology: Application in water samples, soft drink, and cosmetic products.

An exact, rapid and efficient method for the extraction of rhodamine B (RB) and rhodamine 6G (RG) as well as their determination in three different matrices was developed using magnetic stirring assisted dispersive liquid-liquid microextraction (MSA-DLLME) and HPLC-Vis. 1-Octanol and acetone were selected as the extraction and dispersing solvents, respectively. The potentially variables were the volume of extraction and disperser solvents, pH of sample solution, salt effect, temperature, stirring rate and vortex time in the optimization process.

Magnetic stirring-assisted dispersive liquid-liquid microextraction followed by high performance liquid chromatography for determination of phthalate esters in drinking and environmental water samples.

A simple, fast and efficient method for the preconcentration of phthalate esters (PEs) in water samples was developed using magnetic stirring-assisted dispersive liquid-liquid microextraction (MSA-DLLME) followed by high performance liquid chromatography coupled with ultraviolet detection (HPLC-UV). This novel microextraction method is based on the fast injection of extracting solvent into the aqueous solution, which is being stirred by a magnetic stirrer, to form a cloudy binary component solvent (aqueous solution:extracting solvent) system. The extraction parameters such as type and volume of extracting solvent, pH of sample, salt addition, extraction time and stirring rate were optimized.

Preconcentration of trace amounts of methadone in human urine, plasma, saliva and sweat samples using dispersive liquid-liquid microextraction followed by high performance liquid chromatography.

A simple, rapid and efficient method for the preconcentration of methadone was developed using dispersive liquid-liquid microextraction (DLLME) followed by high performance liquid chromatography with ultra violet detection (HPLC-UV). The extraction method is based on the fast injection of a mixture of extracting and disperser solvents into the aqueous solution to form a cloudy ternary component solvent (aqueous solution:extracting solvent:disperser solvent) system. The extraction parameters such as nature and volume of extracting and disperser solvents, pH of sample, and extraction time were studied for optimization.

Utilization of inverted dispersive liquid-liquid microextraction followed by HPLC-UV as a sensitive and efficient method for the extraction and determination of quercetin in honey and biological samples.

A sensitive, rapid and efficient method for the extraction of quercetin as well as its determination in honey and biological samples was developed using inverted dispersive liquid-liquid microextraction (IDLLME) and HPLC-UV. The extraction method is based on the application of an extracting solvent lighter than water in the ternary component solvent (aqueous solution: extracting solvent: disperser solvent) system. The extraction parameters such as type and volume of extracting and disperser solvent, pH of sample, stirring rate and extraction time were optimized.

Application of dispersive liquid-liquid microextraction and spectrophotometric detection to the rapid determination of rhodamine 6G in industrial effluents.

A rapid and effective preconcentration method for extraction of rhodamine 6G was developed by using a dispersive liquid-liquid microextraction (DLLME) prior to UV-vis spectrophotometry. In this extraction method, a suitable mixture of acetone (disperser solvent) and chloroform (extractant solvent) was injected rapidly into a conical test tube containing aqueous solution of rhodamine 6G. Therefore, a cloudy solution was formed.