Monitoring neural stem cell differentiation using PEDOT-PSS based MEA.

BACKGROUND: Transplantation is one potential clinical application of neural stem cells (NSCs). However, it is very difficult to monitor/control NSCs after transplantation and so provide effective treatment. Electrical measurement using a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) modified microelectrode array (MEA) is a biocompatible, non-invasive, non-destructive approach to understanding cell conditions. This property makes continuous monitoring available for the evaluation/assessment of the development of cells such as NSCs. METHODS: A PEDOT-PSS modified MEA was used to monitor electrical signals during NSC development in a culture derived from rat embryo striatum in order to understand the NSC differentiation conditions. RESULTS: Electrical data indicated that NSCs with nerve growth factor (NGF) generate a cultured cortical neuron-like burst pattern while a random noise pattern was measured with epidermal growth factor (EGF) at 4days in vitro (DIV) and a burst pattern was observed in both cases at 11 DIV indicating the successful monitoring of differentiation differences and developmental changes. CONCLUSIONS: The electrical analysis of cell activity using a PEDOT-PSS modified MEA could indicate neural network formation by differentiated neurons. Changes in NSC differentiation could be monitored. GENERAL SIGNIFICANCE: The method is based on non-invasive continuous measurement and so could prove a useful tool for the primary/preliminary evaluation of a pharmaceutical analysis. This article is part of a Special Issue entitled Organic Bioelectronics-Novel Applications in Biomedicine.

AFM observation of single, functioning ionotropic glutamate receptors reconstituted in lipid bilayers.

BACKGROUND: Ionotropic glutamate receptors (iGluRs) are responsible for extracellular signaling in the central nervous system. However, the relationship between the overall structure of the protein and its function has yet to be resolved. Atomic force microscopy (AFM) is an important technique that allows nano-scale imaging in liquid. In the present work we have succeeded in imaging by AFM of the external features of the most common iGluR, AMPA-R (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor), in a physiological environment. METHODS: Homomeric GluR3 receptors were over-expressed in insect cells, purified and reconstituted into lipid membranes. AFM images were obtained in a buffer from membranes immobilized on a mica substrate. RESULTS: Using Au nanoparticle-conjugated antibodies, we show that proteins reconstitute predominantly with the N-terminal domain uppermost on the membrane. A tetrameric receptor structure is clearly observed, but it displays considerable heterogeneity, and the dimensions differ considerably from cryo-electron microscopy measurements. CONCLUSIONS: Our results indicate that the extracellular domains of AMPA-R are highly flexible in a physiological environment. GENERAL SIGNIFICANCE: AFM allows us to observe the protein surface structure, suggesting the possibility of visualizing real time conformational changes of a functioning protein. This knowledge may be useful for neuroscience as well as in pharmaceutical applications.

Ion conducting polymer microelectrodes for interfacing with neural networks.

We have examined the stimulation and recording properties of conjugated polymer microelectrode arrays as interfaces with neural networks of dissociated cortical cells. In particular the stimulation properties were investigated as a means of supplying a neural network with information. The stimulation efficiency at low stimulation voltages was evaluated and referenced to bare indium tin oxide (ITO) electrodes. The polymer electrodes were electrochemically polymerized from a blend of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) and ethylenedioxythiophene (EDOT) onto ITO microelectrodes. Dissociated cortical cells were then plated on the electrodes and cultivated to form neural networks. Polymer electrode stimulation evoked a much greater response from the network than stimulation from ITO electrodes. Neural interfaces using polymer electrodes could be maintained for several months.

Dependence of the Brillouin gain spectrum on linear strain distribution for optical time-domain reflectometer-type strain sensors.

We theoretically derive the shape of the Brillouin gain spectrum, that is, the Briilouin backscattered-light power spectrum produced in an optical fiber under conditions of a strain distribution that changes linearly with a constant slope. The modeled measurement system is an optical time-domain reflectometer-type strain sensor system. The linear strain distribution is one of the fundamental distributions and is produced in, for example, a beam to which a concentrated load is applied. By analyzing a function that expresses the shape of the derived Brillouin gain spectrum, we show that the strain calculated from the frequency at which the spectrum has a peek value coincide. with that at the center of the effective pulsed light. In addition, the peak value and the full width at half maximum of the Brillouin gain spectrum are both influenced by the strain difference between the two ends of the effective pulse. We investigate this influence in detail and obtain the relationship between strain difference and strain measurement error.