Neurons as sensors: individual and cascaded chemical sensing
ABSTRACT A single neuron sensor has been developed based on the interaction of gradient electric fields and the cell membrane. Single neurons are rapidly positioned over individual microelectrodes using positive dielectrophoretic traps. This enables the continuous extracellular electrophysiological measurements from individual neurons. The sensor developed using this technique provides the first experimental method for determining single cell sensitivity; the speed of response and the associated physiological changes to a broad spectrum of chemical agents. Binding of specific chemical agents to a specific combination of receptors induces changes to the extracellular membrane potential of a single neuron, which can be translated into unique "signature patterns" (SP), which function as identification tags. Signature patterns are derived using Fast Fourier Transformation (FFT) analysis and Wavelet Transformation (WT) analysis of the modified extracellular action potential. The validity and the sensitivity of the system are demonstrated for a variety of chemical agents ranging from behavior altering chemicals (ethanol), environmentally hazardous agents (hydrogen peroxide, EDTA) to physiologically harmful agents (pyrethroids) at pico- and femto-molar concentrations. The ability of a single neuron to selectively identify specific chemical agents when injected in a serial manner is demonstrated in "cascaded sensing".
SourceAvailable from: Eddy Luz León
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ABSTRACT: A biosensor is an analytical tool that comprises two essential components, an immobilized bio-component, in intimate contact with a transducer that converts a biological signal into a measurable electrical signal. Both electrochemical and optical transducers are mainly transduction methods that are employed in biosensor developments. This review summarises the studies carried on ethanol determination based on enzyme biosensors, using alcohol dehydogenase (ADH), alcohol oxidase (AOX) or bi-enzyme system, the various techniques of immobilisation, the transducers used and analytical characteristics for biosensor development are described. Almost all enzyme based ethanol biosensors developed are based on the monitoring of NADH in the case of ADH based biosensor, O2 consumption or H2O2 production in the case of AOX biosensor and H2O2 production in the case of thebi-enzyme system. Underlying the importance of this review is the fact that alcohol istoxic above certain concentrations and its continuous real time monitoring in clinical, environmental and food related environments is of utmost interest.