Amperometric biosensor-based flow-through microdetector for microdialysis applications

Conducting polymer-based electrochemical biosensors for neurotransmitters: A review

Neurotransmitters are important biochemical molecules that control behavioral and physiological functions in central and peripheral nervous system. Therefore, the analysis of neurotransmitters in biological samples has a great clinical and pharmaceutical importance. To date, various methods have been developed for their assay. Of the various methods, the electrochemical sensors demonstrated the potential of being robust, selective, sensitive, and real time measurements. Recently, conducting polymers (CPs) and their composites have been widely employed in the fabrication of various electrochemical sensors for the determination of neurotransmitters. Hence, this review presents a brief introduction to the electrochemical biosensors, with the detailed discussion on recent trends in the development and applications of electrochemical neurotransmitter sensors based on CPs and their composites. The review covers the sensing principle of prime neurotransmitters, including glutamate, aspartate, tyrosine, epinephrine, norepinephrine, dopamine, serotonin, histamine, choline, acetylcholine, nitrogen monoxide, and hydrogen sulfide. In addition, the combination with other analytical techniques was also highlighted. Detection challenges and future prospective of the neurotransmitter sensors were discussed for the development of biomedical and healthcare applications.

Review of recent advances in analytical techniques for the determination of neurotransmitters

Methods and advances for monitoring neurotransmitters in vivo or for tissue analysis of neurotransmitters over the last five years are reviewed. The review is organized primarily by neurotransmitter type. Transmitter and related compounds may be monitored by either in vivo sampling coupled to analytical methods or implanted sensors. Sampling is primarily performed using microdialysis, but low-flow push-pull perfusion may offer advantages of spatial resolution while minimizing the tissue disruption associated with higher flow rates. Analytical techniques coupled to these sampling methods include liquid chromatography, capillary electrophoresis, enzyme assays, sensors, and mass spectrometry. Methods for the detection of amino acid, monoamine, neuropeptide, acetylcholine, nucleoside, and soluble gas neurotransmitters have been developed and improved upon. Advances in the speed and sensitivity of these methods have enabled improvements in temporal resolution and increased the number of compounds detectable. Similar advances have enabled improved detection at tissue samples, with a substantial emphasis on single cell and other small samples. Sensors provide excellent temporal and spatial resolution for in vivo monitoring. Advances in application to catecholamines, indoleamines, and amino acids have been prominent. Improvements in stability, sensitivity, and selectivity of the sensors have been of paramount interest.

Fabrication of a multichannel PDMS/glass analytical microsystem with integrated electrodes for amperometric detection

The fabrication process of novel multichannel microfluidic devices with integrated electrodes for amperometric detection is described. Soft-lithography, lift-off and O(2) plasma surface activation sealing techniques were employed for rapid prototyping of cost effective PDMS/glass microchips. The capabilities of the proposed microdevices were demonstrated by the electrooxidation of hydroquinone and N-acetyl-p-aminophenol (APAP) on a Au working electrode at +800 mV and +700 mV, respectively, against a Au pseudo reference electrode, and of thiocyanate on a Cu working electrode at +700 mV against a Ag/AgCl (KCl saturated) reference electrode. Linear response over the range up to 1.0 mmol L(-1) for APAP and up to 4.0 mmol L(-1) for hydroquinone and thiocyanate were verified through calibration curves with correlation coefficients greater than 0.97 (minimum of five data points). The sensitivities for hydroquinone, thiocyanate, and APAP were 28, 19, and 78 microA mol(-1) L, respectively. Under the experimental conditions used, the estimated limits of detection were 0.21, 0.95, and 0.12 mmol L(-1) for hydroquinone, thiocyanate and APAP, respectively. The geometries of the devices were designed to allow fast calibration procedures and reliable results for in-field applications. Exerting a strong influence over the device performance, the sealing process was greatly enhanced by depositing auxiliary TiSiO(2) thin-films. The general performance of the system was verified by amperometric assays of N-acetyl-p-aminophenol standard solutions, and the influences exerted by the present fabrication methods regarding reproducibility and reliability are addressed. The proposed device was successfully applied in the determination of the concentration of APAP in two commercial formulations.