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ABSTRACT: We propose an intrinsic optical method for in vivo neural recording using optic fiber-based surface plasmon resonance (SPR) phenomena. The fiber-based SPR method is electrical artifact free, labeling free, and feasible for a portable system compared with conventional in vivo neural recording systems. We simultaneously detected SPR signals and electrical neural activity from the rat somatosensory cortex evoked by electrical stimulation on the forepaw. Pharmacological analysis using a voltage-gated sodium channel blocker confirmed the neural origins of the optical signals. This fiber-based SPR system promises the enhanced ability to record in vivo neural activity for the investigation of neurons and their networks.
Optics Letters 02/2012; 37(4):614-6. · 3.40 Impact Factor
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ABSTRACT: Patch-clamping or microelectrode arrays (MEA) are conventional methods to monitor the electrical activity in biological neural networks in vitro. Despite the effectiveness of these techniques, there are disadvantages including the limited number of electrodes and the predetermined location of electrodes in MEAs. In particular, these drawbacks raise a difficulty in monitoring a number of neurons outnumbering the electrodes. Here, we propose an optical technique to determine the effective range of focal electrical stimulation using FM dyes in neural networks grown on planar-type MEAs. After 3 weeks in culture, electrical stimulation was delivered to neural networks via an underlying electrode in the presence of FM dyes. The stimulation induced the internalization of the dye into the neurons around the stimulating electrodes. Fluorescent images of dye distribution successfully showed the effects of focal stimulation. A range of stimulus amplitudes and frequencies were examined to collect fluorescence images. FM-dye uptake after electrical stimulation resulted in the labeling of cells up to approximately 300 microm away from the stimulating electrode. Fluorescence intensity increased proportionally to stimulation amplitude. Tetrodotoxin was shown to inhibit the labeling of neurons except those located immediately adjacent (within 40 microm) from the stimulating electrode. In the presence of AMPA and NMDA receptors antagonists, the FM-dye labeling appeared within 80 microm from the electrode, indicating directly evoked neural networks via blocking of glutamatergic synaptic transmission. These results showed that FM dyes can be a useful tool for monitoring activity-dependent synaptic events and determining the effect of focal stimulation in cultured neural networks.
Medical & Biological Engineering 09/2010; 48(9):933-40. · 1.76 Impact Factor
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ABSTRACT: The binding of olfactory receptors with odorant molecules initiates olfactory signal transduction, which leads to a cationic influx. In the present study, human embryonic kidney-293 cells were recombinantly engineered to co-express olfactory receptors I7 and gustatory cyclic nucleotide gated channels, which increased the cationic influx. The odorant-induced change in the membrane potential was measured in the extracellular region using microelectrode arrays. A biphasic electrical current stimulation was applied to the cells in order to increase the intrinsic cellular activity. Upon odorants recognition, the electrical cellular activity was enhanced following each electrical stimulation pulse. Compared with odorant-only stimulation, the electrical stimulation induced up to a fivefold increase in the amplitude of the electrical signal, which was produced in response to the odorants. These results demonstrate that electrical stimulation can enhance cellular activity and increase the response signal for detecting ligand binding. This paradigm of electrical stimulation can be used as a novel method in the field of versatile cell-based biosensors for detection of specific odorants.
Electrophoresis 09/2009; 30(18):3283-8. · 3.30 Impact Factor
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ABSTRACT: The initial event in olfactory perception is the binding of odorant molecules to specific receptor proteins in the human nose. The interaction between odorant and receptor initiates olfactory signal transduction that leads to a cation influx and change in the membrane potential of the olfactory sensory neuron. In this study, a microfabricated planar electrode was used to measure the generated membrane potential in a heterologous olfactory system. Human embryonic kidney (HEK)-293 cells expressing the olfactory receptor I7 were transfected with the gustatory cyclic nucleotide gated (CNG) channel to amplify the membrane potential. A microfabricated planar electrode was used to measure the electrical responses of odorant-receptor binding. Stimulation of the olfactory receptor with its specific odorant caused an intracellular Ca(2+) influx, which was quantitatively measured using a planar electrode. The extracellular field potential generated by the Ca(2+) influx through the CNGgust channel of the cells was approximately 10 mV. This cell-based olfactory biosensor, which uses a microfabricated planar electrode for detection, would be useful for screening specific ligands for binding to orphan olfactory receptors.
Biosensors & bioelectronics 03/2009; 24(8):2659-64. · 5.43 Impact Factor
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Med. Biol. Engineering and Computing. 01/2009; 47:93-99.
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ABSTRACT: Polyacrylamide and poly(ethylene glycol) diacrylate hydrogels were synthesized and characterized for use as drug release and substrates for neuron cell culture. Protein release kinetics was determined by incorporating bovine serum albumin (BSA) into hydrogels during polymerization. To determine if hydrogel incorporation and release affect bioactivity, alkaline phosphatase was incorporated into hydrogels and a released enzyme activity determined using the fluorescence-based ELF-97 assay. Hydrogels were then used to deliver a brain-derived neurotrophic factor (BDNF) from hydrogels polymerized over planar microelectrode arrays (MEAs). Primary hippocampal neurons were cultured on both control and neurotrophin-containing hydrogel-coated MEAs. The effect of released BDNF on neurite length and process arborization was investigated using automated image analysis. An increased spontaneous activity as a response to the released BDNF was recorded from the neurons cultured on the top of hydrogel layers. These results demonstrate that proteins of biological interest can be incorporated into hydrogels to modulate development and function of cultured neural networks. These results also set the stage for development of hydrogel-coated neural prosthetic devices for local delivery of various biologically active molecules.
Journal of Neural Engineering 07/2008; 5(2):203-13. · 3.84 Impact Factor
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ABSTRACT: Planar microelectrode arrays (MEAs) are widely used to record electrical activity from neural networks. However, only a small number of functional recording sites frequently show electrical activity. One contributing factor may be that neurons in vitro receive insufficient synaptic input to develop into fully functional networks. In this study, electrical stimulation was applied to neurons mimicking synaptic input. Various stimulation paradigms were examined. Stimulation amplitude and frequency were tailored to prevent cell death. Two effects of stimulation were observed when 3-week-old cultures were stimulated: (1) clusters of neural cells were observed adjacent to stimulating electrodes and (2) an increase in spontaneous neuronal activity was recorded at stimulating electrodes. Immunocytochemical analysis indicates that stimulation may cause both new neuron process growth as well as astrocyte activation. These data indicate that electrical stimulation can be used as a tool to modify neural networks at specific electrode sites and promote electrical activity.
Medical & Biological Engineering & Computing 12/2007; 45(11):1015-21. · 1.88 Impact Factor
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ABSTRACT: A simplified cochlear implant (CI) system would be appropriate for widespread use in developing countries. Here, we describe a CI that we have designed to realize such a concept. The system implements 8 channels of processing and stimulation using the continuous interleaved sampling (CIS) strategy. A generic digital signal processing (DSP) chip is used for the processing, and the filtering functions are performed with a fast Fourier transform (FFT) of a microphone or other input. Data derived from the processing are transmitted through an inductive link using pulse width modulation (PWM) encoding and amplitude shift keying (ASK) modulation. The same link is used in the reverse direction for backward telemetry of electrode and system information. A custom receiver-stimulator chip has been developed that demodulates incoming data using pulse counting and produces charge balanced biphasic pulses at 1000 pulses/s/electrode. This chip is encased in a titanium package that is hermetically sealed using a simple but effective method. A low cost metal-silicon hybrid mold has been developed for fabricating an intracochlear electrode array with 16 ball-shaped stimulating contacts.
IEEE Transactions on Biomedical Engineering 07/2007; 54(6 Pt 1):973-82. · 2.28 Impact Factor
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ABSTRACT: Synaptic activity recorded from low-density networks of cultured rat hippocampal neurons was monitored using microelectrode arrays (MEAs). Neuronal networks were patterned with poly-l-lysine (PLL) using microcontact printing (microCP). Polydimethysiloxane (PDMS) stamps were fabricated with relief structures resulting in patterns of 2 microm-wide lines for directing process growth and 20 microm-diameter circles for cell soma attachment. These circles were aligned to electrode sites. Different densities of neurons were plated in order to assess the minimal neuron density required for development of an active network. Spontaneous activity was observed at 10-14 days in networks using neuron densities as low as 200 cells/mm(2). Immunocytochemistry demonstrated the distribution of dendrites along the lines and the location of foci of the presynaptic protein, synaptophysin, on neuron somas and dendrites. Scanning electron microscopy demonstrated that single fluorescent tracks contained multiple processes. Evoked responses of selected portions of the networks were produced by stimulation of specific electrode sites. In addition, the neuronal excitability of the network was increased by the bath application of high K(+) (10-12 mM). Application of DNQX, an AMPA antagonist, blocked all spontaneous activity, suggesting that the activity is excitatory and mediated through glutamate receptors.
Journal of Neuroscience Methods 04/2007; 160(2):317-26. · 1.98 Impact Factor
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ABSTRACT: We propose an extracellular optical recording configuration for neuronal action potential detection by using surface plasmon resonance (SPR). The method does not use fluorescence dyes but still taking advantages of optical recording. As a preliminary experiment, the electrochemical SPR effect without neurons was investigated. This showed that a high resolution SPR setup (10<sup>-4</sup>~10<sup>~5</sup> angular shift or more) is required to overcome noise and improve SPR signal. Several issues for neural signal recording are addressed to modify SPR optical configuration
Neural Engineering, 2005. Conference Proceedings. 2nd International IEEE EMBS Conference on; 04/2005
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ABSTRACT: A new cochlear implant system for animal experiments is proposed. The system uses a DSP-based sound processor to implement the six-channel continuous interleaved sampling (CIS) speech processing strategy. An infra-red telemetry is designed to remotely connect the power-demanding sound processor to receiver/stimulator attached on the animal. This enables the animal to move freely. The receiver/stimulator consumes about 40mW, thus can operates for about 200hours without changing battery.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2005; 5:5257-9.
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ABSTRACT: Rectangular networks of rat hippocampal neurons have been produced on microelectrode arrays (MEAs). The crossing points of networks were located at the recording electrode sites by aligned microcontact printing (muCP) technique. Polydimethysiloxane (PDMS) stamp was fabricated to print fine poly-L-lysine (PLL) patterns of 2 mum-width lines for neurites and 20 mum-diameter circles for cell bodies. Different densities of neurons were applied on the PLL-stamped MEAs to find how a low density of neurons still has the functional connectivity. From the neural network applied with a density of 200 cells/mm<sup>2 </sup>, we could observe signal propagation among spontaneous activities. Electrical responses were also evoked by 200 muA current pulse stimulation with 50 mus pulse width. Immunocytostaining was employed to identify dendrites, synapses, and nuclei in the patterned neurons
Engineering in Medicine and Biology Society, 2005. IEEE-EMBS 2005. 27th Annual International Conference of the; 02/2005
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ABSTRACT: A new cochlear implant system for animal experiments is proposed. The system uses a DSP-based sound processor to implement the six-channel continuous interleaved sampling (CIS) speech processing strategy. An infra-red telemetry is designed to remotely connect the power-demanding sound processor to receiver/stimulator attached on the animal. This enables the animal to move freely. The receiver/stimulator consumes about 40 mW, thus can operates for about 200 hours without changing battery
Engineering in Medicine and Biology Society, 2005. IEEE-EMBS 2005. 27th Annual International Conference of the; 02/2005
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[show abstract]
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ABSTRACT: Rectangular networks of rat hippocampal neurons have been produced on microelectrode arrays (MEAs). The crossing points of networks were located at the recording electrode sites by aligned microcontact printing (μCP) technique. Polydimethysiloxane (PDMS) stamp was fabricated to print fine poly-L-lysine (PLL) patterns of 2 -width lines for neurites and 20 -diameter circles for cell bodies. Different densities of neurons were applied on the PLL-stamped MEAs to find how a low density of neurons still has the functional connectivity. From the neural network applied with a density of 200 cells/mm2, we could observe signal propagation among spontaneous activities. Electrical responses were also evoked by 200 current pulse stimulation with 50 pulse width. Immunocytostaining was employed to identify dendrites, synapses, and nuclei in the patterned neurons.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2005; 7:7604-7.
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ABSTRACT: Micromachined glucose sensors were fabricated and integrated with the plasma-treated Ag/AgCl reference electrodes for the first time. The surface of the Cl-plasma exposed AgCl layers was of granule-shaped morphology and showed the favorable long-term stability with a 13-mV potential drift after 5 h over a commercial liquid-junction Ag/AgCl reference electrode in phosphate buffered saline. The fabricated devices showed a typical behavior of an amperometric glucose sensor and a successful operation as a three-electrode system. Due to the integrability of the reference electrode and the use of low-temperature steps only, the new micromachined process can allow easy mass production of the device and the monolithic integration of signal processing circuitry in the future.
IEEE Sensors Journal 07/2003; · 1.52 Impact Factor
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ABSTRACT: The Microelectrode Arrays (MEAs) have been used for several decades to investigate neuronal net-works in vitro. In most of the studies, the neuronal networks have been studied statistically due to complexity of cultured neuronal networks. However, in order to understand the behaviours of neuronal networks dynamically, the identification of synaptic activities of individual neurons is crucial. In this study, we observed individual synaptic activities by utilizing low density neuronal networks arranged orthogonally on MEA's.
