A microgripper sensor device capable of detecting ion efflux from whole cells

Electrothermally actuated microgripper sensor devices that are capable of simultaneous manipulation of live mouse oocytes and the sensing of potassium ion efflux are presented. The ion selective electrode technology applied to a microgripper device yielded a first generation ion sensor with competitive characteristics in selectivity, sensitivity, stability and temporal resolution. The microgripper sensor devices could readily detect the 9 ± 3 mM efflux of potassium ions upon mechanical stimulation. This technology is generic and applicable to generating potentiometric and amperometric sensing microgrippers

Phytoconstituents of Phlogacanthus tubi-florus Nees (Acanthaceae): Phlogacanthin, a new diterpene lactone (andrographolide) isolated from the root wood

1214-121

A G-quadruplex aptamer based impedimetric sensor for free lysine and arginine.

This paper describes a label free sensor for the sensitive detection of certain, basic primary amino acids containing free ethyl and methyl amino acids. The control of interfacial electron transfer of a G-quadruplex DNA aptamer, using a Fe(CN)63–/4− redox probe responds rapidly to variations in arginine and lysine concentrations, but not to histidine, using non-labelled, impedance spectroscopy (EIS) detection. Two binding aptamer binding regimes were observed. At the low concentration range (0–0.15 μg/mL), selectivity between lysine and arginine was apparent with limits of detection at approximately 0.5 pMand 1.6 pM respectively. At higher levels of concentrations, 0.15–10 μg/mL, selectivity was limited. The aptamer was immobilised on gold substrates ensuring optimal probe density which was monitored by Atomic Force Microscopy. Initial studies indicate that the relative change in charge transfer resistance (Rct) values can be used as a parameter for monitoring free lysine to arginine ratios and free total lysine and arginine for direct detection of total lysine and arginine in food samples (milk, egg white and yoghurt) in Tris/HCl buffer, demonstrating its potential in many applications

‘Soft’ electroactive particles and their interaction with lipid membranes.

Solid lipid nanoparticles (SLN) are widely used in pharmaceutical and cosmetic applications. SLN, incorporating approximately 105 ferrocene units, as core-enriched redox active nanoparticles, were used as a model for probing interactions with solid-supported lipid membranes. Resonance Enhanced Surface Impedance Spectroscopy (RESI) is shown as a sensitive technique for monitoring real time interactions of the soft redox nanoparticles. Cyclic voltammetry is compared as an end of experiment technique

Potential of enzyme mimics in biomimetic sensors: a modified-cyclodextrin as a dehydrogenase enzyme mimic

This paper reports the application of a dehydrogenase enzyme mimic as a biomimetic sensor. The model compound investigated was a beta-cyclodextrin (P-CD) derivative with a nicotinamide group attached to the secondary face of a P-CD (Fig. 1g). It was envisaged that the nicotinamide group would act as the electron transfer agent and that the cyclodextrin would provide a suitable hydrophobic cavity for the reaction to take place in. Ethanol, propranalol, dopamine and acetone were used as substrates in backgrounds of hydrophilic and hydrophobic anions. Electrochemical and fluorescence techniques were used to study the catalytic effects in solution. It was found that the size of the analyte and the hydrophobicity of the anion affected the catalytic activity of the dehydrogenase mimic. Catalytic effects were most enhanced with ethanol and dopamine in presence of larger and more strongly SO42- solvated anions, SO42- and H2PO4- which are excluded from the cavity. The molecule was also immobilised in a sol-gel matrix and investigated as a sol-gel electrochemical biomimetic sensor. Concentration dependence with increasing aliquots of ethanol was observed. These results indicated that a re-usable biomimetic sensor is indeed feasible