Hydrogel-coated microelectrode array for neural interface

Recently, hydrogel has been extensively used in various biomedical applications including soft contact lenses, wound healing materials and as a means for controlled drug delivery and release. In this study, we propose to use hydrogel as a novel neural interface. Planar microelectrode arrays were coated with hydrogel in order to improve the quality of the interface and to aid in drug delivery to cells on microelectrode arrays (MEAs).This work was supported by the International Collaboration Program, NBS-ERC (Nano Bioelectronics and Systems Engineering Research Center)/ KOSEF (Korea Science and Engineering Foundation) and also supported in part by the Nanobiotechnology Center (NBTC), an STC Program of the National Science Foundation under Agreement No. ECS-9876771

Optical Monitoring of Neural Network Connectivity Using FM1-43-Evoked Activity from Focal Stimulation of Microelectrode Arrays

This work was supported by the International Collaboration Program NBS-ERC/KOSEF (S.J.K) and by the National Institute of Biomedical Imaging and Bioengineering under Agreement Number R21-EB007782 (M.R.H)

Development of Hybrid Neural Prosthetic Devices

This work was supported by the National Institute of Biomedical Imaging and Bioengineering under Agreement Number R21-EB007782 (M.R.H)

Identification of synaptic activities in microelectrode array-based neural networks

The Microelectrode Arrays (MEAs) have been used for several decades to investigate neuronal networks 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 MEAs.This work was supported by the International Collaboration Program, NBS-ERC (Nano Bioelectronics and Systems Engineering Research Center)/ KOSEF (Korea Science and Engineering Foundation) and NIH, NS-044287, NSF, ECS-9876771

Modulation of Cultured Neural Networks Using Neurotrophin Release

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.This work was supported by the International Collaboration Program, Nano Bioelectronics and Systems Engineering Research Center/Korea Science and Engineering Foundation (R11-2000-075-00002-0), by the Nanobiotechnology Center (NBTC), an STC Program of the National Science Foundation under agreement no. ECS-9876771, the National Institutes of Health under agreement no. R01-NS044287 (WS) and by the National Institute of Biomedical Imaging and Bioengineering under agreement no. R21EB007782 (MRH). The computational image analysiswas supported by the Center for Subsurface Sensing and Imaging Systems (NSF EEC- 9986821). The authors acknowledge use of the Wadsworth Center Advanced Light Microscopy & Image Analysis Core Facility. They would also like to thank Shirley Madewell and Adriana Verschoor for critical review of the manuscript

Electrical Stimulation-Induced Cell Clustering in Cultured Neural Networks

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.This work was supported by the International Collaboration Program, NBS-ERC (Nano Bioelectronics and Systems Engineering Research Center)/KOSEF (Korea Science and Engineering Foundation), NIH, NS-044287 and the Nanobiotechnology Centre (NBTC), an STC program of the National Science Foundation under Agreement Number ECS-9876771. The authors also acknowledge use of the Wadsworth Center Advanced Light Microscopy & Image Analysis Core Facility for the work presented herein

Low-density neuronal networks cultured using patterned poly-l-lysine on microelectrode arrays

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 ( CP). Polydimethysiloxane (PDMS) stamps were fabricated with relief structures resulting in patterns of 2 m-wide lines for directing process growth and 20 m-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/mm2. 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.This work was supported by the International Collaboration Program, NBS-ERC (Nano Bioelectronics and Systems Engineering Research Center)/KOSEF(Korea Science and Engineering Foundation) and NIH, R01NS-044287, NSF, ECS-9876771. Authors also appreciate help from T.H. Lee and J.K. Lee for assistance in the fabrication of MEAs and stamp masters