Electrode Bundles Research Articles

Cochlear implantation in an animal model documents cochlear damage at the tip of the implant

IntroductionElectrocochleography has recently emerged as a diagnostic tool in cochlear implant surgery, purposing hearing preservation and optimal electrode positioning. ObjectiveIn this experimental study, extra-cochlear potentials were obtained during cochlear implant surgery in guinea pigs. The aim was to determine electrophysiological changes indicating cochlear trauma after cochleostomy and after electrode implantation in different insertion depths. MethodsNormal-hearing guinea pigs (n = 14) were implanted uni- or bilaterally with a multichannel electrode. The extra-cochlear cochlear nerve action potentials were obtained in response to acoustic stimuli at specific frequencies before and after cochleostomy, and after introduction of the electrode bundle. After the electrophysiological experiments, the guinea pigs were euthanized and microtomography was performed, in order to determine the position of the electrode and to calculate of the depth of insertion. Based on the changes of amplitude and thresholds in relation to the stimulus frequency, the electrophysiological data and the position obtained by the microtomography reconstruction were compared. ResultsCochleostomy promoted a small electrophysiological impact, while electrode insertion caused changes in the amplitude of extra-cochlear electrophysiological potentials over a wide range of frequencies, especially in the deepest insertions. There was, however, preservation of the electrical response to low frequency stimuli in most cases, indicating a limited auditory impact in the intraoperative evaluation. The mean insertion depth of the apical electrodes was 5339.56 μm (±306.45 – 6 inserted contacts) and 4447.75 μm (±290.23 – 5 inserted contacts). ConclusionsThe main electrophysiological changes observed during surgical procedures occurred during implantation of the electrode, especially the deepest insertions, whereas the cochleostomy disturbed the potentials to a lesser extent. While hearing loss was often observed apical to the cochlear implant, it was possible to preserve low frequencies after insertion.

Impaired hippocampal-cortical coupling but preserved local synchrony during sleep in APP/PS1 mice modeling Alzheimer\u2019s disease

Sleep, in addition to its brain restorative processes, plays an important role in memory transfer from its temporary store in the hippocampus to the more permanent storage in the neocortex. Alzheimer’s disease (AD) affects memory and sleep. The aim of this study was to explore disturbances in global and local synchrony patterns between brain regions in the APP/PS1 mouse model of the AD during natural sleep. We used 8 male APPswe/PS1dE9 mice and 6 wild-type littermates, aged 5–6 months, with multiple electrode bundles implanted into cortical regions, thalamus and hippocampus. We measured video-EEG in freely moving animals and analyzed synchrony during NREM vs REM sleep. Global synchrony between medial frontal cortex and hippocampus measured with magnitude-squared coherence was slightly decreased in delta range during NREM stage of sleep in APP/PS1 mice. In contrast, local hippocampal synchrony measured with cross-frequency coupling remained intact. Ripple structure or frequency did not differ between the genotypes. However, the coupling of the spindle-band power peak in the medial prefrontal cortex to hippocampal ripples was significantly decreased compared to wild-type animals. The delicate timing of hippocampal ripples, frontal delta, and corticothalamic spindle oscillations may be the first sign of impaired memory in amyloid plaque-forming transgenic mice.

The systemDrive: a Multisite, Multiregion Microdrive with Independent Drive Axis Angling for Chronic Multimodal Systems Neuroscience Recordings in Freely Behaving Animals.

A multielectrode system that can address widely separated targets at multiple sites across multiple brain regions with independent implant angling is needed to investigate neural function and signaling in systems and circuits of small animals. Here, we present the systemDrive, a novel multisite, multiregion microdrive that is capable of moving microwire electrode bundles into targets along independent and nonparallel drive trajectories. Our design decouples the stereotaxic surgical placement of individual guide cannulas for each trajectory from the placement of a flexible drive structure. This separation enables placement of many microwire multitrodes along widely spaced and independent drive axes with user-set electrode trajectories and depths from a single microdrive body, and achieves stereotaxic precision with each. The system leverages tight tube-cannula tolerances and geometric constraints on flexible drive axes to ensure concentric alignment of electrode bundles within guide cannulas. Additionally, the headmount and microdrive both have an open-center design to allow for the placement of additional sensing modalities. This design is the first, in the context of small rodent chronic research, to provide the capability to finely position microwires through multiple widely distributed cell groups, each with stereotaxic precision, along arbitrary and nonparallel trajectories that are not restricted to emanate from a single source. We demonstrate the use of the systemDrive in male Long-Evans rats to observe simultaneous single-unit and multiunit activity from multiple widely separated sleep-wake regulatory brainstem cell groups, along with cortical and hippocampal activity, during free behavior over multiple many-day continuous recording periods.

Precision implantation with positional confirmation of fine-wire EMG electrodes in the deep posterior neck muscles

Precise electrode placement is essential for obtaining useful electromyographic (EMG) recordings. Our aim was to develop a protocol for computerized-tomography (CT) guided fine-wire (FW) electrode placement that permits confirmation of the final electrode position in the deep posterior cervical multifidus (CM). FW-EMG electrodes were custom-made from three 50-µm diameter Teflon-insulated platinum/iridium wires. The electrodes were inserted bilaterally in the CM in 15 healthy adult subjects through a 45-mm cannula under CT guidance. The final position of the electrode placement was confirmed in reconstructed 2D and 3D images. Electrode placement was within the fascial boundaries of the CM for 21 of the 25 successfully inserted FW-EMG electrodes. The distance from the electrode to the middle of the CM did not increase significantly with target depth until a breakpoint at 63.2 mm (95%CI 59.1–65.3), from where it increased by an additional 2.9 mm per mm increase in target depth (95%CI 1.3–6.6). Viable EMG was obtained from 21 electrodes. CT guided implantation provided excellent visual documentation in three dimensions of the final placement of the tip of the electrode bundle. The technique affords confidence in studies of motoneuron activity in CM.

Salting the Earth: The Environmental Impact of Oil and Gas Wastewater Spills.

Salting the Earth: The Environmental Impact of Oil and Gas Wastewater Spills.

Electrically evoked compound action potential (ECAP) in cochlear implant children: Changes in auditory nerve response in first year of cochlear implant use

AimRecording of the electrically evoked compound action potential (ECAP) of the auditory nerve in cochlear implant (CI) patients represents an option to assess changes in auditory nerve responses and the interaction between the electrode bundle and the neural tissue over time. The aim of the present work is to assess ECAP changes during the first year of cochlear implant for the purpose of predicting thresholds and adjustment of the patients’ programs over time. MethodData were collected from 25 children using Cochlear Nucleus 24 implants. ECAP thresholds were examined at the time of surgery, at initial stimulation, and 3, 6 and 12 months post-stimulation. Five electrodes located at basal, middle, and apical positions in the cochlea were tested at each time interval and ECAP thresholds were analyzed and compared. ResultsThere was a significant decrease in ECAP thresholds between the intraoperative measure and fitting time at all electrode sites. Mean ECAP thresholds measured at 3, 6 and 12 months post-stimulation remained similar to initial stimulation levels. Although there was no significant difference in ECAP thresholds recorded at fitting time and 12 months follow up session, there was significant increase in behavioral T and C levels from initial stimulation to the 12 months’ time point. ConclusionMost electrodes undergo non-significant change in ECAP thresholds over time, and therefore thresholds obtained on the day of initial stimulation can be used to estimate the patients’ map levels at any time. On the other hand, intraoperative thresholds demonstrated significant change relative to postoperative recording times, limiting the ability to use intraoperatively recorded ECAP thresholds to predict postoperative measurements.

Localization of Metal Electrodes in the Intact Rat Brain Using Registration of 3D Microcomputed Tomography Images to a Magnetic Resonance Histology Atlas.

Simultaneous neural recordings taken from multiple areas of the rodent brain are garnering growing interest because of the insight they can provide about spatially distributed neural circuitry. The promise of such recordings has inspired great progress in methods for surgically implanting large numbers of metal electrodes into intact rodent brains. However, methods for localizing the precise location of these electrodes have remained severely lacking. Traditional histological techniques that require slicing and staining of physical brain tissue are cumbersome and become increasingly impractical as the number of implanted electrodes increases. Here we solve these problems by describing a method that registers 3D computed tomography (CT) images of intact rat brains implanted with metal electrode bundles to a magnetic resonance imaging histology (MRH) atlas. Our method allows accurate visualization of each electrode bundle’s trajectory and location without removing the electrodes from the brain or surgically implanting external markers. In addition, unlike physical brain slices, once the 3D images of the electrode bundles and the MRH atlas are registered, it is possible to verify electrode placements from many angles by “reslicing” the images along different planes of view. Furthermore, our method can be fully automated and easily scaled to applications with large numbers of specimens. Our digital imaging approach to efficiently localizing metal electrodes offers a substantial addition to currently available methods, which, in turn, may help accelerate the rate at which insights are gleaned from rodent network neuroscience.

High-performance aqueous asymmetric supercapacitor based on carbon nanofibers network and tungsten trioxide nanorod bundles electrodes

The demand for high-performance energy storage devices such as supercapacitors and lithium-ion batteries has been increasing to meet the application requirements of renewable energy systems. Here, high energy density aqueous asymmetric supercapacitor (ASC) is assembled based on carbon nanofibers (CNF) network positive electrode and tungsten trioxide (WO3) nanorod bundles negative electrode. Polyaniline-based CNF are prepared by direct carbonization of polyaniline nanofibers. WO3 nanorod bundles are synthesized via a simple sodium chloride assisted hydrothermal process. The CNF//WO3 ASC device operates with a voltage of 1.6V and achieved a high energy density of 35.3 Wh kg−1 at a power density of 314Wkg−1. Furthermore, the device shows an excellent cycling performance with capacitance retention of 88% after 1000 cycles.

Cochlear implantation outcomes in advanced otosclerosis

IntroductionSeveral studies support the use of cochlear implants (CI) in far-advanced otosclerosis (FAO). Material and methodsWe compared our results of CI in patients with FAO and unknown origin hearing loss (UOHL) and our incidence of facial electrical stimulation and difficult insertion of the electrode bundle up to 3 to 5years from surgery. ResultsWe found 17 patients with CI in FAO and UOHL. FAO patients achieved better results on the pure tone average (PTA) and recognition of monosyllables by GEE test (p=0.022; p=0.006), and particularly at 1year on the PTA (p=0.002), at 6months and a year in monosyllables (p=0.002; p=0.001), and at 6months in disyllables (p=0.004). There were no differences toward complications. ConclusionIn our experience, placement of CI in FAO has proven successful, with results comparable to other similar cohorts, and with low complications.

Processing of Hedonic and Chemosensory Features of Taste in Medial Prefrontal and Insular Networks

Most of the research on cortical processing of taste has focused on either the primary gustatory cortex (GC) or the orbitofrontal cortex (OFC). However, these are not the only areas involved in taste processing. Gustatory information can also reach another frontal region, the medial prefrontal cortex (mPFC), via direct projections from GC. mPFC has been studied extensively in relation to its role in controlling goal-directed action and reward-guided behaviors, yet very little is known about its involvement in taste coding. The experiments presented here address this important point and test whether neurons in mPFC can significantly process the physiochemical and hedonic dimensions of taste. Spiking responses to intraorally delivered tastants were recorded from rats implanted with bundles of electrodes in mPFC and GC. Analysis of single-neuron and ensemble activity revealed similarities and differences between the two areas. Neurons in mPFC can encode the chemosensory identity of gustatory stimuli. However, responses in mPFC are sparser, more narrowly tuned, and have a later onset than in GC. Although taste quality is more robustly represented in GC, taste palatability is coded equally well in the two areas. Additional analysis of responses in neurons processing the hedonic value of taste revealed differences between the two areas in temporal dynamics and sensitivities to palatability. These results add mPFC to the network of areas involved in processing gustatory stimuli and demonstrate significant differences in taste-coding between GC and mPFC.

A carbon-fiber electrode array for long-term neural recording

Objective. Chronic neural recording in behaving animals is an essential method for studies of neural circuit function. However, stable recordings from small, densely packed neurons remains challenging, particularly over time-scales relevant for learning. Approach. We describe an assembly method for a 16-channel electrode array consisting of carbon fibers (<5 µm diameter) individually insulated with Parylene-C and fire-sharpened. The diameter of the array is approximately 26 µm along the full extent of the implant. Main results. Carbon fiber arrays were tested in HVC (used as a proper name), a song motor nucleus, of singing zebra finches where individual neurons discharge with temporally precise patterns. Previous reports of activity in this population of neurons have required the use of high impedance electrodes on movable microdrives. Here, the carbon fiber electrodes provided stable multi-unit recordings over time-scales of months. Spike-sorting indicated that the multi-unit signals were dominated by one, or a small number of cells. Stable firing patterns during singing confirmed the stability of these clusters over time-scales of months. In addition, from a total of 10 surgeries, 16 projection neurons were found. This cell type is characterized by sparse stereotyped firing patterns, providing unambiguous confirmation of single cell recordings. Significance. Carbon fiber electrode bundles may provide a scalable solution for long-term neural recordings of densely packed neurons.

Integration of multiple components in polystyrene-based microfluidic devices part I: fabrication and characterization

In Part I of a two-part series, we describe a simple and inexpensive approach to fabricate polystyrene devices that is based upon melting polystyrene (from either a Petri dish or powder form) against PDMS molds or around electrode materials. The ability to incorporate microchannels in polystyrene and integrate the resulting device with standard laboratory equipment such as an optical plate reader for analyte readout and pipets for fluid propulsion is first described. A simple approach for sample and reagent delivery to the device channels using a standard, multi-channel micropipette and a PDMS-based injection block is detailed. Integration of the microfluidic device with these off-chip functions (sample delivery and readout) enables high-throughput screens and analyses. An approach to fabricate polystyrene-based devices with embedded electrodes is also demonstrated, thereby enabling the integration of microchip electrophoresis with electrochemical detection through the use of a palladium electrode (for a decoupler) and carbon-fiber bundle (for detection). The device was sealed against a PDMS-based microchannel and used for the electrophoretic separation and amperometric detection of dopamine, epinephrine, catechol, and 3,4-dihydroxyphenylacetic acid. Finally, these devices were compared against PDMS-based microchips in terms of their optical transparency and absorption of an anti-platelet drug, clopidogrel. Part I of this series lays the foundation for Part II, where these devices were utilized for various on-chip cellular analysis.

Effects of Repeated 3,4-Methylenedioxymethamphetamine Administration on Neurotransmitter Efflux and Sensory-Evoked Discharge in the Ventral Posterior Medial Thalamus

3,4-Methylenedioxymethamphetamine (MDMA) is known to enhance tactile sensory perception, an effect that contributes to its popularity as a recreational drug. The neurophysiological basis for the effects of MDMA on somatosensation are unknown. However, MDMA interactions with the serotonin transporter (SERT) and subsequent enhancement of serotonin neurotransmission are well known. The rat trigeminal somatosensory system receives serotonergic afferents from the dorsal raphe nucleus. Because these fibers express SERT, they should be vulnerable to MDMA-induced effects. We found that administration of a challenge injection of MDMA (3 mg/kg i.p.) after repeated MDMA treatment (3 mg/kg per day for 4 days) elicits both serotonin and norepinephrine efflux in the ventral posterior medial (VPM) thalamus of Long-Evans hooded rats, the main relay along the lemniscal portion of the rodent trigeminal somatosensory pathway. We evaluated the potential for repeated MDMA administration to modulate whisker-evoked discharge of individual neurons in this region. After surgically implanting stainless steel eight-wire multichannel electrode bundles, we recorded spike train activity of single cells while activating the whisker pathway using a piezoelectric mechanical stimulator. We found that repeated MDMA administration increased the spontaneous firing rate but reduced both the magnitude and duration of whisker-evoked discharge in individual VPM thalamic neurons. The time course of drug action on neuronal firing patterns was generally consistent with fluctuations in neurotransmitter efflux as shown from our microdialysis studies. On the basis of these results, we propose that single use and repeated administration of MDMA may "distort," rather than enhance, tactile experiences in humans, in part, by disrupting normal spike firing patterns through somatosensory thalamic relay circuits.

Longitudinal study of the ecap measured in children with cochlear implants

SummaryIn children with cochlear implant (CI), the recording of the electrically evoked compound action potential (ECAP) of the auditory nerve represents an option to assess changes in auditory nerve responses and the interaction between the electrode bundle and the neural tissue over time. Aim: To study ECAP in children during the first year of CI use. Materials and methods: The ECAP characteristics have been analyzed in 13 children implanted younger than three years of age. Series study. Results: During the first year of CI use there was a significant statistical raise in the N1 peak amplitude, in basal electrodes, between the second and third return visits. There were not any significant differences obtained for N1 peak, latency, slope, p-NRT or recovery time, in the return visits. Conclusion: During the first year of CI use, the electrical stimulation provided by the intracochlear electrodes did not cause significant changes to ECAP characteristics, except for an increase in N1 peak amplitude.

The multi-channel cochlear implant: Past, present and future perspectives

Initial research demonstrated that only low frequencies could be mimicked with rate of electrical stimulation, and thus multi-channel rather than single-channel stimulation was required for the place coding of the mid-high speech frequencies.Place coding of mid-high frequencies was best achieved with electrodes inside the cochlea. Furthermore, correct biomechanical properties of a multiple electrode bundle were required for it to pass around the cochlear spiral to the speech frequency region.Biological studies showed too that intra-cochlear electrodes could be used with minimal trauma, safe electrical stimulus parameters, and methods to prevent inner ear infection and meningitis.The crucial discoveries for coding speech with electrical stimulation have been based on the discovery of: 1) the fact the brain processes frequency information along spatial and temporal channels, and 2) that the first patient experienced vowels when stimulating different electrodes that corresponded to the place of excitation for single formant vowels in people with normal hearing. The inaugural and subsequent speech processing strategies extracted frequencies of special importance for speech intelligibility, and transmitted the information along place coding channels. The voicing frequency and/or amplitude, was coded as temporal information across these spatial channels. As a result a great majority of severely-to-profoundly deaf people with previous hearing can not only communicate when electrical stimulation is combined with lipreading, but with electrical stimulation alone. In addition, the benefits of binaural hearing with bilateral cochlear implants or an implant in one ear and hearing aid in the other ear have been realized.Related psychophysical research has discovered the basic perceptual skills that process the complex patterns of brain excitation that underlie speech recognition both in the one ear as well as bilateral implants.In addition the development of the perceptual skills in the maturing child for speech recognition, have been discovered.In the future high fidelity sound should be achieved by providing the fine temporo-spatial patterns of excitation and preserving the peripheral nerve network. This could require the release of nerve growth factors and the development of electrodes using nanotechnology. Copyright © 2009 John Wiley & Sons, Ltd.

MDMA (3,4-Methylenedioxymethamphetamine)-Mediated Distortion of Somatosensory Signal Transmission and Neurotransmitter Efflux in the Ventral Posterior Medial Thalamus

MDMA (3,4-methylenedioxymethamphetamine, Ecstasy) is reported to enhance tactile sensory perception, an effect that is believed to contribute to its popularity as a recreational drug. To date, no literature exists that addresses the neurophysiological mechanisms underlying the effects of MDMA on somatosensation. However, MDMA interactions with the serotonin transporter protein (SERT) are well known. The rat trigeminal somatosensory system has been studied extensively and receives serotonergic afferents from the dorsal raphe nucleus. Given that these fibers express SERT, they should be vulnerable to MDMA-induced effects. We found that short-term low-dose MDMA administration (3 mg/kg i.p.) led to a significant increase in 5-hydroxytryptamine (5-HT) efflux in the ventral posterior medial (VPM) thalamus, the main relay along the lemniscal portion of the rodent trigeminal somatosensory pathway. We further evaluated the potential for MDMA to modulate whisker-evoked discharge (WED) of individual neurons in this region. After surgically implanting stainless steel 8-wire multichannel electrode bundles, we recorded spike train activity from single cells of halothane-anesthetized rats while mechanically activating the whisker pathway. We found that short-term low-dose MDMA (3 mg/kg i.p.) increased the spontaneous firing rate but reduced the magnitude and duration of WED in individual VPM thalamic neurons. It is noteworthy that the time course of drug action on neuronal firing patterns was generally consistent with increased 5-HT efflux as shown from our microdialysis studies. Based on these results, we propose the working hypothesis that MDMA may "distort" rather than enhance tactile experiences in humans, in part, by disrupting normal spike firing patterns through somatosensory thalamic relay circuits.

Estudo anatômico da cóclea para confecção de instrumental para a cirurgia de implante coclear com 2 feixes de eletrodos em cócleas ossificadas

A ossificação da cóclea, decorrente principalmente de meningite, impede a inserção completa do implante coclear convencional. Os implantes com 2 feixes de eletrodos mais curtos do que o convencional foram desenvolvidos especialmente para cócleas ossificadas. Porém, durante essa cirurgia há um grande risco de lesão da artéria carótida interna (ACI). Portanto, a medida da profundidade das cocleostomias para inserir os dois feixes de eletrodos aumentaria a segurança desse procedimento. OBJETIVOS: 1) Obter as distâncias entre as cocleostomias e a ACI em ossos temporais de cadáver; 2) Confeccionar instrumento que possa ser usado na cirurgia de implante coclear com 2 feixes de eletrodos. FORMA DE ESTUDO: Experimental prospectivo. MATERIAL E MÉTODO: Em 21 ossos de cadáveres foi realizada: 1) mastoidectomia cavidade aberta; 2) cocleostomias nos giros basal e médio da cóclea; 3) identificação da ACI; 4) medida da distância entre as cocleostomias e a artéria. RESULTADOS: A medida média ± desvio padrão obtida para o túnel superior foi 8,2 ± 1,1mm e para o túnel inferior foi 8,1± 1,3mm. A menor distância encontrada foi 6,5mm para o túnel superior e 6,0mm para o túnel inferior. CONCLUSÃO: Apesar dos parâmetros calculados concluímos que a melhor medida para ser considerada na confecção do instrumento cirúrgico serão as mínimas medidas obtidas em cada um dos giros cocleares, pois é a maneira mais segura para evitar a lesão da ACI, que pode ser fatal.

Cochlear anatomy study used to design surgical instruments for cochlear implants with two bundles of electrodes in ossified cochleas

SummaryCochlear ossification, mainly secondary to meningitis, prevents the complete conventional cochlear implant insertion. Implants with two electrode bundles shorter than the conventional ones were specifically developed for ossified cochleas. However, during surgery there is a high risk of damaging the internal carotid artery (ICA). Therefore, measuring cochleostomy depth in order to insert the two electrode bundles would greatly increase the procedure's safety.Aims1) Find the distances between cochleostomies and ICA in cadaver temporal bones. 2) Design an instrument that can be used in cochlear implant surgery to introduce an implant with two bundles of electrodes.Study DesignExperimental prospective.Materials and MethodsIn 21 temporal bones from cadavers we performed: 1) canal wall down mastoidectomy; 2) cochleostomy in the cochlear basal and middle turns; 3) ICA identification; 4) Length determination between the cochleostomies and the artery.Resultsthe average distance ± standard deviation obtained for the upper tunnel was of 8.2 ± 1.1 mm and for the lower tunnel it was of 8.1± 1.3 mm. The shortest distance found was of 6.5 mm for the upper tunnel and 6.0 mm for the lower tunnel.ConclusionDespite the values calculated, we concluded that the best value to be considered in creating a surgical instrument are the minimum lengths obtained for each one of the cochlear turns, because this is the safest way to avoid damaging the ICA, that can be fatal.

The synthetic cannabinoid HU210 induces spatial memory deficits and suppresses hippocampal firing rate in rats.

Previous work implied that the hippocampal cannabinoid system was particularly important in some forms of learning, but direct evidence for this hypothesis is scarce. We therefore assessed the effects of the synthetic cannabinoid HU210 on memory and hippocampal activity. HU210 (100 microg kg(-1)) was administered intraperitoneally to rats under three experimental conditions. One group of animals were pre-trained in spatial working memory using a delayed-matching-to-position task and effects of HU210 were assessed in a within-subject design. In another, rats were injected before acquisition learning of a spatial reference memory task with constant platform location. Finally, a separate group of animals was implanted with electrode bundles in CA1 and CA3 and single unit responses were isolated, before and after HU210 treatment. HU210 treatment had no effect on working or short-term memory. Relative to its control Tween 80, deficits in acquisition of a reference memory version of the water maze were obtained, along with drug-related effects on anxiety, motor activity and spatial learning. Deficits were not reversed by the CB(1) receptor antagonists SR141716A (3 mg kg(-1)) or AM281 (1.5 mg kg(-1)). Single unit recordings from principal neurons in hippocampal CA3 and CA1 confirmed HU210-induced attenuation of the overall firing activity lowering both the number of complex spikes fired and the occurrence of bursts. These data provide the first direct evidence that the underlying mechanism for the spatial memory deficits induced by HU210 in rats is the accompanying abnormality in hippocampal cell firing.

Combinatorial micro electrochemistry. Part 4: Cyclic voltammetric redox screening of homogeneous ruthenium(II) hydrogenation catalysts

Organometallic ruthenium(II) complexes, which act as homogeneous hydrogenation catalysts, are characterized electrochemically with respect to their redox properties by means of a new screening technique (“redox screening”). Samples of the complexes are dissolved in an electrolyte and placed in the wells of microtiter plates. Electrode bundles are moved under computer control between these wells, and cyclic voltammograms are automatically recorded. Analysis of the current/potential curves shows a relation between the voltammogram shape or position and the catalytic activity of the complexes. Thus, the technique proves well suited as an electrochemistry-based high-throughput method.