A General Synthetic Route to Indenofluorene Derivatives As New Organic Semiconductors

Organic Letters. Mar, 2005  |  Pubmed ID: 15727443

A series of 2,6-disubstituted indenofluorene derivatives were obtained in high purity via a general route involving the Suzuki coupling reaction. The potential of these conjugated indenofluorenes as new organic semiconductors was demonstrated by the light-emitting diode reaching a high luminance of 1400 Cd/m(2) below 10 V. [structure: see text]

Neurogenesis and Neuronal Communication on Micropatterned Neurochips

Biotechnology and Bioengineering. Nov, 2005  |  Pubmed ID: 16094670

Neural networks are formed by accurate connectivity of neurons and glial cells in the brain. These networks employ a three-dimensional bio-surface that both assigns precise coordinates to cells during development and facilitates their connectivity and functionality throughout life. Using specific topographic and chemical features, we have taken steps towards the development of poly(dimethylsiloxane; PDMS) neurochips that can be used to generate and study synthetic neural networks. These neurochips have micropatterned structures that permit adequate cell positioning and support cell survival. Within days of plating, cells differentiate into neurons displaying excitability and communication, as evidenced by intracellular calcium oscillations and action potentials. The structural and functional capacities of such simple neural networks open up new opportunities to study synaptic communication and plasticity.

Nanotemplating for Two-dimensional Molecular Imprinting

Langmuir : the ACS Journal of Surfaces and Colloids. May, 2007  |  Pubmed ID: 17407335

A new 2D molecular imprinting technique based on nanotemplating and soft-lithography techniques is reported. This technique allows the creation of target-specific synthetic recognition sites on different substrates using a uniquely oriented and immobilized template and the attachment of a molecularly imprinted polymer on a substrate. The molecularly imprinted polymer was characterized by AFM, fluorescence microscopy, and ATR-FTIR. We evaluated the rebinding ability of the sites with theophylline (the target molecule). The selectivity of the molecularly imprinted polymer was determined for the theophylline-caffeine couple. The molecularly imprinted polymer exhibited selectivity for theophylline, as revealed by competitive rebinding experiments. Fluorescence microscopy experiments provided complementary proof of the selectivity of the molecularly imprinted polymer surfaces toward theophylline. These selective molecularly imprinted polymers have the potential for chemical sensor applications. Because of its 2D nature, this novel chemical sensor technology can be integrated with many existing high-sensitivity multichannel detection technologies.

High-contrast Organic Light Emitting Diodes with a Partially Absorbing Anode

Optics Letters. May, 2008  |  Pubmed ID: 18483534

To be legible in high-ambient light conditions, organic light-emitting-diode displays should be optically designed to have a minimal reflectance without significantly affecting their overall efficiency. We demonstrate the use of an anode consisting of a partially absorbing metal layer and a multilayer distributed Bragg reflector to simultaneously absorb rather than reflect incoming light and to take advantage of a weak microcavity effect in the diode to improve light outcoupling.

Design of High-contrast OLEDs with Microcavity Effect

Optics Express. May, 2008  |  Pubmed ID: 18545510

There is a large demand for Organic Light-Emitting Displays (OLEDs) with higher contrast, particularly for outdoor applications. We show that lowering the reflectance of OLEDs, which is required for increasing the contrast, can also lead to a reduction of their efficiency when a small microcavity effect is not maintained in their structure. We describe in details the design of high-contrast bottom-emitting OLEDs that have low reflectance but still maintain a small cavity effect for efficient emission.

Cell Placement and Guidance on Substrates for Neurochip Interfaces

Biotechnology and Bioengineering. Feb, 2010  |  Pubmed ID: 19753615

Interface devices such as integrated planar patch-clamp chips are being developed to study the electrophysiological activity of neuronal networks grown in vitro. The utility of such devices will be dependent upon the ability to align neurons with interface features on the chip by controlling neuronal placement and by guiding cell connectivity. In this paper, we present a strategy to accomplish this goal. Patterned chemical modification of SiN surfaces with poly-d-lysine transferred from PDMS stamps was used to promote adhesion and guidance of cryo-preserved primary rat cortical neurons. We demonstrate that these neurons can be positioned and grown over microhole features which will ultimately serve as patch-clamp interfaces on the chip.

A Novel Silicon Patch-clamp Chip Permits High-fidelity Recording of Ion Channel Activity from Functionally Defined Neurons

Biotechnology and Bioengineering. Nov, 2010  |  Pubmed ID: 20648547

We report on a simple and high-yield manufacturing process for silicon planar patch-clamp chips, which allow low capacitance and series resistance from individually identified cultured neurons. Apertures are etched in a high-quality silicon nitride film on a silicon wafer; wells are opened on the backside of the wafer by wet etching and passivated by a thick deposited silicon dioxide film to reduce the capacitance of the chip and to facilitate the formation of a high-impedance cell to aperture seal. The chip surface is suitable for culture of neurons over a small orifice in the substrate with minimal leak current. Collectively, these features enable high-fidelity electrophysiological recording of transmembrane currents resulting from ion channel activity in cultured neurons. Using cultured Lymnaea neurons we demonstrate whole-cell current recordings obtained from a voltage-clamp stimulation protocol, and in current-clamp mode we report action potentials stimulated by membrane depolarization steps. Despite the relatively large size of these neurons, good temporal and spatial control of cell membrane voltage was evident. To our knowledge this is the first report of recording of ion channel activity and action potentials from neurons cultured directly on a planar patch-clamp chip. This interrogation platform has enormous potential as a novel tool to readily provide high-information content during pharmaceutical assays to investigate in vitro models of disease, as well as neuronal physiology and synaptic plasticity.

High-fidelity Patch-clamp Recordings from Neurons Cultured on a Polymer Microchip

Biomedical Microdevices. Dec, 2010  |  Pubmed ID: 20694518

We present a polymer microchip capable of monitoring neuronal activity with a fidelity never before obtained on a planar patch-clamp device. Cardio-respiratory neurons Left Pedal Dorsal 1 (LPeD1) from mollusc Lymnaea were cultured on the microchip's polyimide surface for 2 to 4 hours. Cultured neurons formed high resistance seals (gigaseals) between the cell membrane and the surface surrounding apertures etched in the polyimide. Gigaseal formation was observed without applying external force, such as suction, on neurons. The formation of gigaseals, as well as the low access resistance and shunt capacitance values of the polymer microchip resulted in high-fidelity recordings. On-chip culture of neurons permitted, for the first time on a polymeric patch-clamp device, the recording of high fidelity physiological action potentials. Microfabrication of the hybrid poly(dimethylsiloxane)-polyimide (PDMS-PI) microchip is discussed, including a two-layer PDMS processing technique resulting in minimized shrinking variations.

Patch-clamp Array Neurochips: Value in Interrogating Simple Neuronal Networks with High Resolution

Expert Review of Medical Devices. Jan, 2011  |  Pubmed ID: 21158534

Cell to Aperture Interaction in Patch-clamp Chips Visualized by Fluorescence Microscopy and Focused-ion Beam Sections

Biotechnology and Bioengineering. Aug, 2011  |  Pubmed ID: 21391207

Patch-clamp is an important method to monitor the electrophysiological activity of cells and the role of pharmacological compounds on specific ion channel proteins. In recent years, planar patch-clamp chips have been developed as a higher throughput approach to the established glass-pipette method. However, proper conditions to optimize the high resistance cell-to-probe seals required to measure the small currents resulting from ion channel activity are still the subject of conjecture. Here, we report on the design of multiple-aperture (sieve) chips to rapidly facilitate assessment of cell-to-aperture interactions in statistically significant numbers. We propose a method to pre-screen the quality of seals based on a dye loading protocol through apertures in the chip and subsequent evaluation with fluorescence confocal microscopy. We also show the first scanning electron micrograph of a focused ion beam section of a cell in a patch-clamp chip aperture.

Recordings of Cultured Neurons and Synaptic Activity Using Patch-clamp Chips

Journal of Neural Engineering. Jun, 2011  |  Pubmed ID: 21540486

Planar patch-clamp chip technology has been developed to enhance the assessment of novel compounds for therapeutic efficacy and safety. However, this technology has been limited to recording ion channels expressed in isolated suspended cells, making the study of ion channel function in synaptic transmission impractical. Recently, we developed single- and dual-recording site planar patch-clamp chips and demonstrated their capacity to record ion channel activity from neurons established in culture. Such capacity provides the opportunity to record from synaptically connected neurons cultured on-chip. In this study we reconstructed, on-chip, a simple synaptic circuit between cultured pre-synaptic visceral dorsal 4 neurons and post-synaptic left pedal dorsal 1 neurons isolated from the mollusk Lymnaea stagnalis. Here we report the first planar patch-clamp chip recordings of synaptic phenomena from these paired neurons and pharmacologically demonstrate the cholinergic nature of this synapse. We also report simultaneous dual-site recordings from paired neurons, and demonstrate dedicated cytoplasmic perfusion of individual neurons via on-chip subterranean microfluidics. This is the first application of planar patch-clamp technology to examine synaptic communication.

From Understanding Cellular Function to Novel Drug Discovery: the Role of Planar Patch-clamp Array Chip Technology

Frontiers in Pharmacology. 2011  |  Pubmed ID: 22007170

All excitable cell functions rely upon ion channels that are embedded in their plasma membrane. Perturbations of ion channel structure or function result in pathologies ranging from cardiac dysfunction to neurodegenerative disorders. Consequently, to understand the functions of excitable cells and to remedy their pathophysiology, it is important to understand the ion channel functions under various experimental conditions - including exposure to novel drug targets. Glass pipette patch-clamp is the state of the art technique to monitor the intrinsic and synaptic properties of neurons. However, this technique is labor intensive and has low data throughput. Planar patch-clamp chips, integrated into automated systems, offer high throughputs but are limited to isolated cells from suspensions, thus limiting their use in modeling physiological function. These chips are therefore not most suitable for studies involving neuronal communication. Multielectrode arrays (MEAs), in contrast, have the ability to monitor network activity by measuring local field potentials from multiple extracellular sites, but specific ion channel activity is challenging to extract from these multiplexed signals. Here we describe a novel planar patch-clamp chip technology that enables the simultaneous high-resolution electrophysiological interrogation of individual neurons at multiple sites in synaptically connected neuronal networks, thereby combining the advantages of MEA and patch-clamp techniques. Each neuron can be probed through an aperture that connects to a dedicated subterranean microfluidic channel. Neurons growing in networks are aligned to the apertures by physisorbed or chemisorbed chemical cues. In this review, we describe the design and fabrication process of these chips, approaches to chemical patterning for cell placement, and present physiological data from cultured neuronal cells.