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Abstract: There is an enduring quest for technologies that provide – temporally and spatially – highly resolved information on electric neuronal or cardiac activity in functional tissues or cell cultures. Here, we present a planar high-density, low-noise microelectrode system realized in microelectronics technology that features 11,011 microelectrodes (3,150 electrodes per mm2), 126 of which can be arbitrarily selected and can, via a reconfigurable routing scheme, be connected to on-chip recording and stimulation circuits. This device enables long-term extracellular electrical-activity recordings at subcellular spatial resolution and microsecond temporal resolution to capture the entire dynamics of the cellular electrical signals. To illustrate the device performance, extracellular potentials of Purkinje cells (PCs) in acute slices of the cerebellum have been analyzed. A detailed and comprehensive picture of the distribution and dynamics of action potentials (APs) in the somatic and dendritic regions of a single cell was obtained from the recordings by applying spike sorting and spike-triggered averaging methods to the collected data. An analysis of the measured local current densities revealed a reproducible sink/source pattern within a single cell during an AP. The experimental data substantiated compartmental models and can be used to extend those models to better understand extracellular single-cell potential patterns and their contributions to the population activity. The presented devices can be conveniently applied to a broad variety of biological preparations, i.e., neural or cardiac tissues, slices, or cell cultures can be grown or placed directly atop of the chips for fundamental mechanistic or pharmacological studies. [Copyright &y& Elsevier]

Abstract: A strategy for patterned cell adhesion based on chemical surface modification is presented. To confine cell adhesion to specific locations, an engineered surface for high-contrast protein adsorption and, hence, cell attachment has been developed. Surface functionalization is based on selective molecular-assembly patterning (SMAP). An amine-terminated self-assembled monolayer is used to define areas of cell adhesion. A protein-repellent grafted copolymer, poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG), is used to render the surrounding silicon dioxide resistant to protein adsorption. X-ray photoelectron spectroscopy, scanning ellipsometry and fluorescence microscopy techniques were used to monitor the individual steps of the patterning process. Successful guided growth using these layers is demonstrated with primary neonatal rat cardiomyocytes, up to 4 days in vitro, and with the HL-1 cardiomyocyte cell line, up to 7 days in vitro. The advantage of the presented method is that high-resolution engineered surfaces can be realized using a simple, cost-effective, dip-and-rinse process. The technique has been developed for application on a CMOS cell-based biosensor, which comprises an array of microelectrodes to extracellularly record electrical activity from cardiomyocytes. [Copyright &y& Elsevier]

Cross sections for simultaneous electron capture and target ion excitation have been measured for impact of slow He-like C and N ions on He. The energy of the primary ion beams has been varied over more than two orders of magnitude: 0.05-7 keV/amu. The results are discussed on basis of a slightly modified version of the 'dynamic' classical over-barrier model for multiple electron capture. The differences in the energy dependences of the experimental results of C and N - He can be explained qualitatively by assuming that for N binding energy sharing between the two participating electrons is of importance, particularly at the lower impact energies. [ABSTRACT FROM AUTHOR]

In the impact velocity range of 0.2-0.6 a.u. we have measured line emission cross sections in the vuv and visible spectral region for collisions of C with atomic hydrogen. The electron capture goes predominantly into the n=4 shell and to a lesser extent into the n=5 shell. For the dominant lines there is a good agreement with the molecular, the extended atomic and the unified atomic-molecular orbital calculations of respectively Green et al. [8], Fritsch and Lin [9], and Kimura and Lin [10]. However for transitions originating from the n=5 level the measurements strongly support the molecular orbital calculations. Furthermore there are considerable differences between measured and calculated intensities for the lines of non-dominantly populated high- n states ( n=7 and 8) and atomic orbital and UDWA calculations. [ABSTRACT FROM AUTHOR]

We have determined absolute cross sections for electron capture into the quasi-degenerate 4l states of He produced in collisions of He on atomic hydrogen. The cross sections have been deduced by deconvoluting spatial HeII( n = 4 → n= 3) emission profiles. The measurements have been perfored in the impact energy range of 2−130 keV/amu. The results are compared with theory. In addition we discuss the relevance of these cross sections to α-particle diagnostics in fusion plasmas. At the JET tokamak the HeII( n= 4 → n= 3) emission can be used to determine related quantities like ion temperature, plasma rotation and local α-particle densities. [ABSTRACT FROM AUTHOR]