Apparatus and method of inserting a microelectrode in body tissue or the like using vibration means

An arrangement for and method of inserting a glass microelectrode having a tip in the micron range into body tissue is presented. The arrangement includes a microelectrode. The top of the microelectrode is attached to the diaphragm center of a first speaker. The microelectrode tip is brought into contact with the tissue by controlling a micromanipulator. Thereafter, an audio signal is applied to the speaker to cause the microelectrode to vibrate and thereby pierce the tissue surface without breaking the microelectrode tip. Thereafter, the tip is inserted into the tissue to the desired depth by operating the micromanipulator with the microelectrode in a vibratory or non-vibratory state

Sonochemically fabricated microelectrode arrays for biosensors. Part II. Modification with a polysiloxane coating

A polymer modified sonochemically fabricated glucose oxidase microelectrode array with microelectrode population densities of up to 2.5 x 105 microelectrodes cm-2 is reported. These microelectrode sensors were formed by first depositing an insulating film on commercial screen printed electrodes which was subsequently sonicated to form cavities of regular sizes in the film. Electropolymerisation of aniline at the microelectrode cavities formed polyaniline protrusions containing entrapped glucose oxidase. Chemical deposition of polysiloxane from dichlorodimethysilane was used to deposit a thin protective and diffusion mass transport controlling coating over the electrodes. The physical and electrochemical properties of these films were studied. The performance of the final glucose oxidase based microelectrode sensor array is reported

Intraneural stimulation using 2D wire-microelectrode arrays: II. Comparison with single-wire electrode results

A two-dimensional wire-microelectrode array was inserted into the peroneal nerve of the rat through an incision. For each of the electrodes in the array the corresponding twitch-force recruitment curve was recorded from the extensor digitorum longus muscle (EDL). The mean value and standard deviation of the threshold current were found to be not significantly different from those for single wire electrodes. This suggests that the incision does not introduce significant (additional) current leakag

Mass-transport resistances of acid and alkaline ionomer layers: A microelectrode study part 1 - Microelectrode development

The use of microelectrodes to study localized mass-transport phenomena in fuel-cell catalyst layers is an increasingly valuable tool. However, existing microelectrode cells have been used in static, equilibrated environment modes with poorly controlled interfaces. In this work, we present a microelectrode cell design that expands the experimental space addressable by microelectrodes to include mechanical pressure, gas flow and ionomer medium, and experimental throughput. The feasibility of the design is examined for fuel-cell reactions, with oxygen reduction currents independent of mechanical pressure and gas flowrate. Finally, cell equilibration time and IR drop across the electrolyte are estimated. The new cell design is robust and provides a consistent base from which to perform more complicated studies examining mass-transport properties of ionomers and/or the electrochemical reaction kinetics of hydrogen oxidation and oxygen reduction

Electrochemical microsensors for cutaneous surface analysis: Application to the determination of pH and the antioxidant properties of stratum corneum

Potentiometry and cyclic voltammetry were proposed as simple, reliable and non invasive methods for the simultaneous determination of pH and antioxidant properties of skin. Experiments were performed with microelectrodes just deposited on skin surface without any gel or water added. pH was measured by means of the zero current potential of a tungsten W/WO3 sensor. A nerstian response was recorded in pH range 4 to 6 corresponding to the normal skin pH values. The global antioxidant capacity was deduced from the anodic charge passed during the plotting of cyclic voltammograms on platinum or gold microelectrodes. Comparing the half wave or peak potentials of these curves with those recorded for experiments performed in aqueous solution, the main hydrophilic antioxidants species were detected, i.e. ascorbic acid, uric acid and glutathione. This relatively easy-to-use analytical method made it possible to follow in real time the efficiency of topic treatment as well as to study the influence of oxidative stres

Dielectrophoretic trapping of dissociated fetal cortical rat neurons

Recording and stimulating neuronal activity at multiple sites can be realized with planar microelectrode arrays. Efficient use of such arrays requires each site to be covered by at least one neuron. By application of dielectrophoresis (DEP), neurons can be trapped onto these sites. This study investigates negative dielectrophoretic trapping of fetal cortical rat neurons. A planar quadrupole microelectrode structure was used for the creation of a nonuniform electric field. The field was varied in amplitude (1, 3, and 5 V) and frequency (10 kHz-50 MHz). Experimental results were compared with a theoretical model to investigate the yield (the number of neurons trapped in the center of the electrode structure) with respect to time, amplitude and frequency of the field. The yield was a function of time1/3 according to theory. However, unlike the model predicted, an amplitude-dependent frequency behavior was present and unexpected peaks occurred in the DEP-spectra above 1 MHz. Gain/phase measurements showed a rather unpredictable behavior of the electrode plate above 1 MHz, and temperature measurement showed that heating of the medium influenced the trapping effect, especially for larger amplitudes and higher frequencie

Using microelectrode models for real time cell-culture monitoring

This paper proposes a cell-microelectrode model for cell biometry applications, based on the area overlap as main parameter. The model can be applied to cell size identification, cell count, and their extension to cell growth and dosimetry protocols. Experiments performed with comercial electrodes are presented, illustrating a procedure to obtain cell number in both growth and dosimetry processes. Results obtained for the AA8 cell line are promising.Junta de Andalucía P0-TIC-538