Integration of high charge injection capacity electrodes onto polymer softening neural interfaces (original) (raw)
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Journal of Neural Engineering, 2019
Objective: The goal of this study was to evaluate the long-term behavior of the surface electrode through electrochemical characterization and follow up of implanted parylene/platinum microelectrodes. Approach: To this aim, we designed and manufactured specific planar electrodes for cortical implantation for a rat model. This work was included in the INTENSE® project, one of the goals of which was to prove the feasibility of selective neural recording or stimulation with cuff electrodes around the vagus nerve. Main results: After a 12-week implantation on a rat model, we can report that these microelectrodes have withstood in-vivo use. Regarding the biocompatibility of the electrodes (materials and manufacturing process), no adverse effect was reported. Indeed, after the three months implantation, we characterized limited tissue reaction beneath the electrodes and showed an increase and a stabilization of their impedance. Interestingly, the follow up of the electrochemical impedance combined with electrical stimulation highlighted a drop of the impedance up to 60% @1kHz after ten minutes of electrical stimulation at 110Hz.
Journal of Neural Engineering, 2021
Objective. Previous studies demonstrated the possibility to fabricate stereo-electroencephalography probes with high channel count and great design freedom, which incorporate macro-electrodes as well as micro-electrodes offering potential benefits for the pre-surgical evaluation of drug resistant epileptic patients. These new polyimide probes allowed to record local field potentials, multi-and single-unit activity (SUA) in the macaque monkey as early as 1 h after implantation, and yielded stable SUA for up to 26 d after implantation. The findings opened new perspectives for investigating mechanisms underlying focal epilepsy and its treatment, but before moving to possible human application, safety data are needed. In the present study we evaluate the tissue response of this new neural interface by assessing post-mortem the reaction of brain tissue along and around the probe implantation site. Approach. Three probes were implanted, independently, in the brain of one monkey (Macaca mulatta) at different times. We used specific immunostaining methods for visualizing neuronal cells and astrocytes, for measuring the extent of damage caused by the probe and for relating it with the implantation time. Main results. The size of the region where neurons cannot be detected did not exceed the size of the probe, indicating that a complete loss of neuronal cells is only present where the probe was physically positioned in the brain. Furthermore, around the probe shank, we observed a slightly reduced number of neurons within a radius of 50 µm and a modest increase in the number of astrocytes within 100 µm. Significance. In the light of previous electrophysiological findings, the present data suggest the potential usefulness and safety of this probe for human applications.
IEEE Transactions on Neural Systems and Rehabilitation Engineering, 2019
Reliable chronic neural recording from focal deep brain structures is impeded by insertion injury and foreign body response, the magnitude of which is correlated with the mechanical mismatch between the electrode and tissue. Thin and flexible electrodes cause less glial scarring and record longer than stiff electrodes. However, insertion of flexible microelectrodes into the brain has been a challenge. Here, a novel insertion method is proposed, and demonstrated, for precise targeting deep brain structures using flexible micro-wire electrodes. The microelectrode is spun and slowly inserted in the brain through an appropriate electrode guide. The electrode guide does not penetrate into cortex. Based on two new mechanisms, namely spinning and guided insertion, we have demonstrated successful insertion of 25 micron platinum flexible electrodes about 10 millimeter deep in rat brain without buckling. We present an electrode insertion device based on the proposed method and demonstrate its use to implant flexible microelectrodes in rat brains. The step-by-step insertion process is described. Microelectrodes were inserted in the Bötzinger complex of 11 rat brains and chronic respiratory neural activity was recorded from 2 rats for 50 days.
A guide towards long-term functional electrodes interfacing neuronal tissue
Journal of Neural Engineering, 2018
Implantable electronics address therapeutical needs of patients with electrical signaling dysfunctions such as heart problems, neurological disorders or hearing impairments. While standard electronics are rigid, planar and made of hard materials, their surrounding biological tissues are soft, wet and constantly in motion. These intrinsic differences in mechanical and chemical properties cause physiological responses that constitute a fundamental challenge to create functional long-term interfaces. Using soft and stretchable materials for electronic implants decreases the mechanical mismatch between implant and biological tissues. As a result, tissue damage during and after implantation is reduced, leading not only to an attenuated foreign body response, but also enabling completely novel applications. However, but for a few exceptions, soft materials are not sufficient to create long-term stable functional implants. In this work, we review recent progress in interfacing both the central (CNS) and peripheral nervous system (PNS) for long-term functional devices. The basics of soft and stretchable devices are introduced by highlighting the importance of minimizing physical as well as mechanical mismatch between tissue and implant in the CNS and emphasizing the relevance of an appropriate surface chemistry for implants in the PNS. Finally, we report on the latest materials and techniques that provide further electronic enhancements while reducing the foreign body reaction. Thus, this review should serve as a guide for creating long-term functional implants to enable future healthcare technologies and as a discussion on current ideas and progress within the field.
Evaluation of permanent implantation of electrodes within the brain
Electroencephalography and Clinical Neurophysiology, 1955
1. Techniques of construction and implantation of multilead electrodes in the brain of animals are described. Technical problems of implantation are examined.2. No operatory accidents occured, and no deficits were produced by electrode insertion.3. After several months of implantation, plate electrodes produced a small impression on the brain surface without histological alteration of the neurons. Damage of the brain resulting from needle electrodes was generally less than 1 mm. in diameter. Infections were rare. Electrocoagulation was more hazardous.4. Prolonged electrical stimulation of the brain did not cause any detectable local histological changes.5. Cerebral stimulation was possible in cats and monkeys which had freedom of movement. This permitted studies concerning behavior, sensory phenomena, correlations between clinical manifestations and electrical activity of the brain, and also psychological testing of the animals.6. Patterns of response evoked by electrical stimulation proved to be typical for each point, and reliable through time.7. Thresholds of electrical stimulation proved to be rather constant throughout the months of observation.8. “Spontaneous” electrical activity and patterns of evoked post discharges recorded by means of implanted electrodes were similar in recordings taken with weeks or months of interval.9. Conclusions 6, 7, and 8 indicate that the presence of electrodes disturbs the brain activity very little, or at least, that the experimental conditions do not change during the period of observation.
Journal of Neural Engineering, 2020
Innovation in electrode design has produced a myriad of new and creative strategies for interfacing the nervous system with softer, less invasive, more broadly distributed sites with high spatial resolution. However, despite rapid growth in the use of implanted electrode arrays in research and clinical applications, there are no broadly accepted guiding principles for the design of biocompatible chronic recording interfaces in the central nervous system (CNS). Studies suggest that the architecture and flexibility of devices play important roles in determining effective tissue integration: device feature dimensions (varying from 'sub'to 'supra'-cellular scales, <10 µm to >100 µm), Young's modulus, and bending modulus have all been identified as key features of design. However, critical knowledge gaps remain in the field with respect to the underlying motivation for these designs: (1) a systematic study of the relationship between device design features (materials, architecture, flexibility), biointegration, and signal quality needs to be performed, including controls for interaction effects between design features, (2) benchmarks for success need to be determined (biological integration, recording performance, longevity, stability), and (3) user results, particularly those that champion a specific design or electrode modification, need to be replicated across laboratories. Finally, the ancillary effects of factors such as tethering, site impedance and insertion method need to be considered. Here, we briefly review observations to-date of device design effects on tissue integration and performance, and then highlight the need for comprehensive and systematic testing of these effects moving forward.
Behavior Research Methods, 2009
We recently developed a glue-based method for the implantation of intracranial electrodes in mice. Our approach is to secure a preconstructed electrode array using a cyanoacrylate-based glue (similar to Krazy Glue). This method is applicable to both young and aging mice and is suitable for long-term electroencephalographic recordings. In the present experiment, we explored whether the glue-based method is capable of securing individual electrodes in addition to securing the electrode array. C57 black mice aged 25-35 days or 13-19 months were operated on under isoflurane anesthesia. Monopolar or bipolar electrodes were inserted independently in the ipsilateral hippocampal CA3 and entorhinal cortical areas, and they were fixed onto the skull using the glue together with dental acrylic, but without anchoring screws. We found that the implanted electrodes were stable and allowed repeat intracranial recordings and electrical stimulation in freely moving mice.
Conducting polymers for neural interfaces: Challenges in developing an effective long-term implant
Biomaterials, 2008
Metal electrode materials used in active implantable devices are often associated with poor long-term stimulation and recording performance. Modification of these materials with conducting polymer coatings has been suggested as an approach for improving the neural tissue-electrode interface and increasing the effective lifetime of these implants. Neural interfaces ideally have intimate contact between the excitable tissue and the electrode to maintain signal quality and activation of neural cells. The outcomes of current research into conducting polymers as coatings has potential to enhance this tissuematerial contact by increasing the electrode surface area and roughness as well as allowing delivery of bioactive signals to neural cells. However, challenges facing conducting polymers include poor electroactive stability and mechanical properties as well as control of the mobility, concentration and presentation of bioactive molecules. The impact of biological inclusions on polymer properties and their ongoing performance in neural prosthetics requires a greater understanding with future research aimed at controlling and optimising film characteristics for long-term performance. Optimising the electrode interface will require a trade-off between desired electrical, mechanical, chemical and biological properties.
Stabilizing electrode-host interfaces: a tissue engineering approach
Journal of rehabilitation research and development
The stability of implanted electrodes is a significant problem affecting their long-term use in vivo. Problems include mechanical failure and inflammation at the implantation site. The engineering of bioactive electrode coatings has been investigated for its potential to promote in-growth of neural tissue and reduce sheer at the electrode-host interface. Preliminary results indicate that hydrogel coatings with either collagen I or polylysine-laminin-1 can promote cortical nerve cell attachment and differentiation on silicon substrates. Additionally, slow-release microtubules can also be implanted in these gels to release agents that either provide trophic support to neurons or prevent inflammation locally. When silicon discs are coated with collagen type I, the coating remains stable for 55 days. Further testing is underway, but initial results indicate that tissue-engineering approaches provide useful insights to help address the problem of host-electrode instability in the brain.
Plastic neuronal probes for implantation in cortical and subcortical areas of the rat brain
International Journal of Nanotechnology, 2012
We discuss the fabrication of flexible implantable probes for recording neuronal activity in the rat brain. We fabricated such probes bearing 12 platinum electrodes, using polyimide as a substrate and SU-8 as an insulation layer. The fabrication process was simplified through the use of laser ablation to define the probe outline. The probes showed not only good mechanical flexibility but also the required stiffness for implantation. Histology results and electrical recordings of neuronal activity lend support to the idea that the combination of polyimide and SU-8 represents a good choice of materials for the fabrication of implantable neuronal probes.