Controlled delivery for neuro-bionic devices

Low-intensity pulsed ultrasound stimulation (LIPUS) modulates microglial activation following intracortical microelectrode implantation

Microglia are important players in surveillance and repair of the brain. Implanting an electrode into the cortex activates microglia, produces an inflammatory cascade, triggers the foreign body response, and opens the blood-brain barrier. These changes can impede intracortical brain-computer interfaces performance. Using two-photon imaging of implanted microelectrodes, we test the hypothesis that low-intensity pulsed ultrasound stimulation can reduce microglia-mediated neuroinflammation following the implantation of microelectrodes. In the first week of treatment, we found that low-intensity pulsed ultrasound stimulation increased microglia migration speed by 128%, enhanced microglia expansion area by 109%, and a reduction in microglial activation by 17%, indicating improved tissue healing and surveillance. Microglial coverage of the microelectrode was reduced by 50% and astrocytic scarring by 36% resulting in an increase in recording performance at chronic time. The data indicate that low-intensity pulsed ultrasound stimulation helps reduce the foreign body response around chronic intracortical microelectrodes.

Low-intensity pulsed ultrasound stimulation (LIPUS) modulates microglial activation following intracortical microelectrode implantation

Microglia are important players in surveillance and repair of the brain. Their activation mediates neuroinflammation caused by intracortical microelectrode implantation, which impedes the application of intracortical brain-computer interfaces (BCIs). While low-intensity pulsed ultrasound stimulation (LIPUS) can attenuate microglial activation, its potential to modulate the microglia-mediated neuroinflammation and enhance the bio-integration of microelectrodes remains insufficiently explored. We found that LIPUS increased microglia migration speed from 0.59±0.04 to 1.35±0.07 µm/hr on day 1 and enhanced microglia expansion area from 44.50±6.86 to 93.15±8.77 µm 2 /min on day 7, indicating improved tissue healing and surveillance. Furthermore, LIPUS reduced microglial activation by 17% on day 6, vessel-associated microglia ratio from 70.67±6.15 to 40.43±3.87% on day 7, and vessel diameter by 20% on day 28. Additionally, microglial coverage of the microelectrode was reduced by 50% in week 1, indicating better tissue-microelectrode integration. These data reveal that LIPUS helps resolve neuroinflammation around chronic intracortical microelectrodes.

Biopolymeric Coatings for Local Release of Therapeutics from Biomedical Implants

The deployment of structures that enable localized release of bioactive molecules can result in more efficacious treatment of disease and better integration of implantable bionic devices. The strategic design of a biopolymeric coating can be used to engineer the optimal release profile depending on the task at hand. As illustrative examples, here advances in delivery of drugs from bone, brain, ocular, and cardiovascular implants are reviewed. These areas are focused to highlight that both hard and soft tissue implants can benefit from controlled localized delivery. The composition of biopolymers used to achieve appropriate delivery to the selected tissue types, and their corresponding outcomes are brought to the fore. To conclude, key factors in designing drug-loaded biopolymeric coatings for biomedical implants are highlighted.

Soft Fiber Electronics Based on Semiconducting Polymer

Fibers, originating from nature and mastered by human, have woven their way throughout the entire history of human civilization. Recent developments in semiconducting polymer materials have further endowed fibers and textiles with various electronic functions, which are attractive in applications such as information interfacing, personalized medicine, and clean energy. Owing to their ability to be easily integrated into daily life, soft fiber electronics based on semiconducting polymers have gained popularity recently for wearable and implantable applications. Herein, we present a review of the previous and current progress in semiconducting polymer-based fiber electronics, particularly focusing on smart-wearable and implantable areas. First, we provide a brief overview of semiconducting polymers from the viewpoint of materials based on the basic concepts and functionality requirements of different devices. Then we analyze the existing applications and associated devices such as information interfaces, healthcare and medicine, and energy conversion and storage. The working principle and performance of semiconducting polymer-based fiber devices are summarized. Furthermore, we focus on the fabrication techniques of fiber devices. Based on the continuous fabrication of one-dimensional fiber and yarn, we introduce two- and three-dimensional fabric fabricating methods. Finally, we review challenges and relevant perspectives and potential solutions to address the related problems.

3D Bioelectronics with a Remodellable Matrix for Long-Term Tissue Integration and Recording

Bioelectronics hold the key for understanding and treating disease. However, achieving stable, long-term interfaces between electronics and the body remains a challenge. Implantation of a bioelectronic device typically initiates a foreign body response, which can limit long-term recording and stimulation efficacy. Techniques from regenerative medicine have shown a high propensity for promoting integration of implants with surrounding tissue, but these implants lack the capabilities for the sophisticated recording and actuation afforded by electronics. Combining these two fields can achieve the best of both worlds. Here, the construction of a hybrid implant system for creating long-term interfaces with tissue is shown. Implants are created by combining a microelectrode array with a bioresorbable and remodellable gel. These implants are shown to produce a minimal foreign body response when placed into musculature, allowing one to record long-term electromyographic signals with high spatial resolution. This device platform drives the possibility for a new generation of implantable electronics for long-term interfacing.

Last Resort Interventions?: A Qualitative Study of Psychiatrists' Experience with and Views on Psychiatric Electroceutical Interventions

Psychiatrists play an important role in providing access to psychiatric electrical interventions (PEIs) such as electroconvulsive therapy (ECT) and transcranial magnetic stimulation (TMS). As such, their views on these procedures likely influence whether they refer or provide these types of treatments for their clinically depressed patients. Despite this, scholars have too infrequently examined psychiatrists' views about specific PEIs and have not yet examined their views across different PEIs. To gain insight into psychiatrists' views about PEIs, we conducted a qualitative study based on semi-structured interviews with 16 psychiatrists in Michigan. The majority of psychiatrists had a positive attitude towards PEIs in general. One-third reported cautionary attitudes towards PEIs; they did not reject the interventions but were skeptical of their effectiveness or felt they needed further development. The majority of psychiatrists consider ECT and TMS to be viable therapies that they would discuss with their patients after several failed medication trials. There was a lack of knowledge about surgical PEIs, such as deep brain stimulation. This study provides insights into how psychiatrists perceive PEIs. While broadly positive attitudes exist, this research highlights certain challenges, particularly lack of knowledge and ambiguity about the use of PEIs.

A 3D Microscaffold Cochlear Electrode Array for Steroid Elution

In cochlear implants, the electrode insertion trauma during surgery can cause damage residual hearing. Preserving the residual hearing is an important challenge and the localized administration of drugs, such as steroids, is one of the most promising ways, but remains a challenge. Here, a microscaffold cochlear electrode array (MiSCEA) consisting of a microfabricated flexible electrode array and a 3D microscaffold for steroid reservoir is reported. The MiSCEA without loaded drug is tested by measuring the electrically evoked auditory brainstem response of the cochlea in guinea pigs (n = 4). The scaffold is then coated with steroid (dexamethasone) encapsulated in polylactic-co-glycolic acid and the continuous release of the steroid into artificial perilymph during six weeks is monitored. The steroid-containing scaffolds are then implanted into guinea pigs (n = 4) and threshold shifts are analyzed for four weeks by measuring the acoustically evoked auditory brainstem response. The threshold shifts tend to be lower in the group implanted with the steroid-containing MiSCEAs. The feasibility of 3D MiSCEA opens up the development of potential next-generation cochlear electrode with improved steroid release dynamics into cochlea.

The Effects of Closed-Loop Brain Implants on Autonomy and Deliberation: What are the Risks of Being Kept in the Loop?

Neuroethics Now welcomes articles addressing the ethical application of neuroscience in research and patient care, as well as its impact on society.

Electroactive polymers for tissue regeneration: Developments and perspectives

Human body motion can generate a biological electric field and a current, creating a voltage gradient of -10 to -90 mV across cell membranes. In turn, this gradient triggers cells to transmit signals that alter cell proliferation and differentiation. Several cell types, counting osteoblasts, neurons and cardiomyocytes, are relatively sensitive to electrical signal stimulation. Employment of electrical signals in modulating cell proliferation and differentiation inspires us to use the electroactive polymers to achieve electrical stimulation for repairing impaired tissues. Electroactive polymers have found numerous applications in biomedicine due to their capability in effectively delivering electrical signals to the seeded cells, such as biosensing, tissue regeneration, drug delivery, and biomedical implants. Here we will summarize the electrical characteristics of electroactive polymers, which enables them to electrically influence cellular function and behavior, including conducting polymers, piezoelectric polymers, and polyelectrolyte gels. We will also discuss the biological response to these electroactive polymers under electrical stimulation. In particular, we focus this review on their applications in regenerating different tissues, including bone, nerve, heart muscle, cartilage and skin. Additionally, we discuss the challenges in tissue regeneration applications of electroactive polymers. We conclude that electroactive polymers have a great potential as regenerative biomaterials, due to their ability to stimulate desirable outcomes in various electrically responsive cells.

A Dual-layered Microfluidic System for Long-term Controlled In Situ Delivery of Multiple Anti-inflammatory Factors for Chronic Neural Applications

We report the development of a microfluidic system capable of repeated infusions of anti-inflammatory factors post-implantation for use as a coating for neural probes. This system consists of a microchannel in a thin gelatin methacryloyl (GelMA)-polyethylene glycol (PEG) composite hydrogel surrounded by a porous polydimethylsiloxane (PDMS) membrane, where the hydrogel can be dried to increase the stiffness for easy insertion. Reswelling allowed us to perfuse interleukin (IL)-4 and dexamethasone (DEX) as anti-inflammatory factors through the channel with minimal burst release and significant amounts of IL-4 were observed to release for up to 96 hr post-infusion. Repeated injections of IL-4 increased the ratio of prohealing M2 versus proinflammatory M1 phenotypes of macrophages encapsulated in the hydrogel by six fold compared with a single injection, over a 2-week period. These repeated infusions also significantly downregulated the expression of inflammatory markers tumor necrosis factor (TNF)-α and IL-6 in astrocytes encapsulated in hydrogel. To demonstrate the system as a coating of neural probe for in vivo applications, we further fabricated a prototype device, where a thin dual-layered microfluidic system was integrated onto a metal probe. Such a drug delivery system could help reduce the formation of a glial scar around neural probes.

Recent developments in drug eluting devices with tailored interfacial properties

Drug eluting devices have greatly evolved during past years to become fundamental products of great marketing importance in the biomedical field. There is currently a large diversity of highly specialized devices for specific applications, making the development of these devices an exciting field of research. The replacement of the former bare metal devices by devices loaded with drugs allowed the sustained and controlled release of drugs, to achieve the desired local therapeutic concentration of drug. The newer devices have been "engineered" with surfaces containing micro- and nanoscale features in a well-controlled manner, that have shown to significantly affect cellular and subcellular function of various biological systems. For example, the topography can be structured to form an antifouling surface mimicking the defense mechanisms found in nature, like the skin of the shark. In the case of bone implants, well-controlled nanostructured interfaces can promote osteoblast differentiation and matrix production, and enhance short-term and long-term osteointegration. In any case, the goal of current research is to design implants that induce controlled, guided, and rapid healing. This article reviews recent trends in the development of drug eluting devices, as well as recent developments on the micro/nanotechnology scales, and their future challenges. For this purpose medical devices have been divided according to the different systems of the body they are focused to: orthopedic devices, breathing stents, gastrointestinal and urinary systems, devices for cardiovascular diseases, neuronal implants, and wound dressings.

Conducting Polymer Microcups for Organic Bioelectronics and Drug Delivery Applications

An ideal neural device enables long-term, sensitive, and selective communication with the nervous system. To accomplish this task, the material interface should mimic the biophysical and the biochemical properties of neural tissue. By contrast, microfabricated neural probes utilize hard metallic conductors, which hinder their long-term performance because these materials are not intrinsically similar to soft neural tissue. This study reports a method for the fabrication of monodisperse conducting polymer microcups. It is demonstrated that the physical surface properties of conducting polymer microcups can be precisely modulated to control electrical properties and drug-loading/release characteristics.

Templating the 3D structure of conducting polymers with self-assembling peptides

Polymerization of pre-assembled peptide–thiophene monomers produced electrically conductive gels with fibrous, porous structures.

Coatings of Different Carbon Nanotubes on Platinum Electrodes for Neuronal Devices: Preparation, Cytocompatibility and Interaction with Spiral Ganglion Cells

Cochlear and deep brain implants are prominent examples for neuronal prostheses with clinical relevance. Current research focuses on the improvement of the long-term functionality and the size reduction of neural interface electrodes. A promising approach is the application of carbon nanotubes (CNTs), either as pure electrodes but especially as coating material for electrodes. The interaction of CNTs with neuronal cells has shown promising results in various studies, but these appear to depend on the specific type of neurons as well as on the kind of nanotubes. To evaluate a potential application of carbon nanotube coatings for cochlear electrodes, it is necessary to investigate the cytocompatibility of carbon nanotube coatings on platinum for the specific type of neuron in the inner ear, namely spiral ganglion neurons. In this study we have combined the chemical processing of as-delivered CNTs, the fabrication of coatings on platinum, and the characterization of the electrical properties of the coatings as well as a general cytocompatibility testing and the first cell culture investigations of CNTs with spiral ganglion neurons. By applying a modification process to three different as-received CNTs via a reflux treatment with nitric acid, long-term stable aqueous CNT dispersions free of dispersing agents were obtained. These were used to coat platinum substrates by an automated spray-coating process. These coatings enhance the electrical properties of platinum electrodes, decreasing the impedance values and raising the capacitances. Cell culture investigations of the different CNT coatings on platinum with NIH3T3 fibroblasts attest an overall good cytocompatibility of these coatings. For spiral ganglion neurons, this can also be observed but a desired positive effect of the CNTs on the neurons is absent. Furthermore, we found that the well-established DAPI staining assay does not function on the coatings prepared from single-wall nanotubes.

pHEMA Encapsulated PEDOT-PSS-CNT Microsphere Microelectrodes for Recording Single Unit Activity in the Brain

The long-term reliability of neural interfaces and stability of high-quality recordings are still unsolved issues in neuroscience research. High surface area PEDOT-PSS-CNT composites are able to greatly improve the performance of recording and stimulation for traditional intracortical metal microelectrodes by decreasing their impedance and increasing their charge transfer capability. This enhancement significantly reduces the size of the implantable device though preserving excellent electrical performances. On the other hand, the presence of nanomaterials often rises concerns regarding possible health hazards, especially when considering a clinical application of the devices. For this reason, we decided to explore the problem from a new perspective by designing and testing an innovative device based on nanostructured microspheres grown on a thin tether, integrating PEDOT-PSS-CNT nanocomposites with a soft synthetic permanent biocompatible hydrogel. The pHEMA hydrogel preserves the electrochemical performance and high quality recording ability of PEDOT-PSS-CNT coated devices, reduces the mechanical mismatch between soft brain tissue and stiff devices and also avoids direct contact between the neural tissue and the nanocomposite, by acting as a biocompatible protective barrier against potential nanomaterial detachment. Moreover, the spherical shape of the electrode together with the surface area increase provided by the nanocomposite deposited on it, maximize the electrical contact and may improve recording stability over time. These results have a good potential to contribute to fulfill the grand challenge of obtaining stable neural interfaces for long-term applications.

Insinuating electronics in the brain

There is an expanding interface between electronic engineering and neurosurgery. Rapid advances in microelectronics and materials science, driven largely by consumer demand, are inspiring and accelerating development of a new generation of diagnostic, therapeutic, and prosthetic devices for implantation in the nervous system. This paper reviews some of the basic science underpinning their development and outlines some opportunities and challenges for their use in neurosurgery.

A Threat to Autonomy? The Intrusion of Predictive Brain Implants

The world's first-in-human clinical trial using invasive intelligent brain devices—devices that predict specific neuronal events directly to the implanted person—has been completed with significant success. Predicting brain activity before specific outcomes occur brings a raft of unprecedented applications, especially when implants offer advice on how to respond to the neuronal events forecasted. Although these novel predictive and advisory implantable devices offer great potential to positively affect patients following surgery by enhancing quality of life (e.g., provide control over symptoms), substantial ethical concerns remain. The invasive nature of these novel devices is not unique; however, the inclusion of predictive and advisory functionalities within the implants, involving permanent monitoring of brain activity in real time, raises new ethical issues to explore, especially in relation to concerns for patient autonomy. What might be the effects of ongoing monitoring of predictive and advisory brain technologies on a patient's postoperative sense of autonomy? The role played by predictive and advisory implantable brain devices on patient's feelings of autonomy following surgery is completely unknown. The first section of this article addresses this shortcoming by reporting on a pilot study that we conducted with one of the patients implanted with one of these novel brain devices. The second section examines how overreliance on predictive and advisory brain technologies may threaten patients' autonomy. The third section looks into ethical problems concerning how devices delivering automated therapeutic responses might, hypothetically speaking, be used to monitor and control individual's autonomy through inhibition of undesirable behaviors.

Classification, processing and application of hydrogels: A review

This article aims to review the literature concerning the choice of selectivity for hydrogels based on classification, application and processing. Super porous hydrogels (SPHs) and superabsorbent polymers (SAPs) represent an innovative category of recent generation highlighted as an ideal mould system for the study of solution-dependent phenomena. Hydrogels, also termed as smart and/or hungry networks, are currently subject of considerable scientific research due to their potential in hi-tech applications in the biomedical, pharmaceutical, biotechnology, bioseparation, biosensor, agriculture, oil recovery and cosmetics fields. Smart hydrogels display a significant physiochemical change in response to small changes in the surroundings. However, such changes are reversible; therefore, the hydrogels are capable of returning to its initial state after a reaction as soon as the trigger is removed.

Electroactive hybrid hydrogel: Toward a smart coating for neural electrodes

Electroactive hybrid hydrogels, composed of single-walled carbon nanotubes, polypyrrole, and poly(ethylene glycol) diacrylate–polyacrylamide, were synthesized on titanium-mesh electrodes via interfacial polymerization. The modified electrodes can be used as controlled drug delivery system by applying an external electrical stimulation of cyclic voltammetry. Investigations revealed that single-walled carbon nanotubes acted as nucleators in the hybrid hydrogel and facilitated the formation of a continuous and uniform polypyrrole coating. Simultaneous incorporation of single-walled carbon nanotubes and polypyrrole improved not only the electrochemical performance but also the drug loading capacity of the hydrogel. Study of dexamethasone release triggered by cyclic voltammetry indicated that the hybrid hydrogel exhibited good electrochemical stability, a high drug loading capacity, and a linear and sustaining drug release profile, making the modified electrode a novel high-performance drug delivery device. Moreover, in vitro experiments demonstrated that dexamethasone released from the modified electrodes well retained its bioactivity, having the same effect on reducing lipopolysaccharide-induced macrophage activation as the intact commercially available dexamethasone. More important, the obtained modified electrodes possessed good biocompatibility with neural cells, demonstrated by in vitro cell culture.

Electroactive Tissue Scaffolds with Aligned Pores as Instructive Platforms for Biomimetic Tissue Engineering

Tissues in the body are hierarchically structured composite materials with tissue-specific chemical and topographical properties. Here we report the preparation of tissue scaffolds with macroscopic pores generated via the dissolution of a sacrificial supramolecular polymer-based crystal template (urea) from a biodegradable polymer-based scaffold (polycaprolactone, PCL). Furthermore, we report a method of aligning the supramolecular polymer-based crystals within the PCL, and that the dissolution of the sacrificial urea yields scaffolds with macroscopic pores that are aligned over long, clinically-relevant distances (i.e., centimeter scale). The pores act as topographical cues to which rat Schwann cells respond by aligning with the long axis of the pores. Generation of an interpenetrating network of polypyrrole (PPy) and poly(styrene sulfonate) (PSS) in the scaffolds yields electroactive tissue scaffolds that allow the electrical stimulation of Schwann cells cultured on the scaffolds which increases the production of nerve growth factor (NGF).

Peptide-directed assembly of functional supramolecular polymers for biomedical applications: electroactive molecular tongue-twisters (oligoalanine–oligoaniline–oligoalanine) for electrochemically enhanced drug delivery

We report the preparation and characterization of films of electroactive supramolecular polymers based on non-electroactive oligoalanines and electroactive oligoanilines.

Multiphoton microfabrication of conducting polymer-based biomaterials

Multiphoton microfabrication was used to prepare CP-based materials for drug delivery and stimulating tissues.

Anti-inflammatory polymer electrodes for glial scar treatment: bringing the conceptual idea to future results

Conducting polymer films offer a convenient route for the functionalization of implantable microelectrodes without compromising their performance as excellent recording units. A micron thick coating, deposited on the surface of a regular metallic electrode, can elute anti-inflammatory drugs for the treatment of glial scarring as well as growth factors for the support of surrounding neurons. Electro-activation of the polymer drives the release of the substance and should ideally provide a reliable method for controlling quantity and timing of release. Driving signals in the form of a constant potential (CP), a slow redox sweep or a fast pulse are all represented in literature. Few studies present such release in vivo from actual recording and stimulating microelectronic devices. It is essential to bridge the gap between studies based on release in vitro, and the intended application, which would mean release into living and highly delicate tissue. In the biological setting, signals are limited both by available electronics and by the biological safety. Driving signals must not be harmful to tissue and also not activate the tissue in an uncontrolled manner. This review aims at shedding more light on how to select appropriate driving parameters for the polymer electrodes for the in vivo setting. It brings together information regarding activation thresholds for neurons, as well as injury thresholds, and puts this into context with what is known about efficient driving of release from conducting polymer films.

A review of organic and inorganic biomaterials for neural interfaces

Recent advances in nanotechnology have generated wide interest in applying nanomaterials for neural prostheses. An ideal neural interface should create seamless integration into the nervous system and performs reliably for long periods of time. As a result, many nanoscale materials not originally developed for neural interfaces become attractive candidates to detect neural signals and stimulate neurons. In this comprehensive review, an overview of state-of-the-art microelectrode technologies provided fi rst, with focus on the material properties of these microdevices. The advancements in electro active nanomaterials are then reviewed, including conducting polymers, carbon nanotubes, graphene, silicon nanowires, and hybrid organic-inorganic nanomaterials, for neural recording, stimulation, and growth. Finally, technical and scientific challenges are discussed regarding biocompatibility, mechanical mismatch, and electrical properties faced by these nanomaterials for the development of long-lasting functional neural interfaces.

Biodegradable electroactive polymers for electrochemically-triggered drug delivery

We report biodegradable electroactive polymer (EAP)-based materials and their application as drug delivery devices.

Investigation of nerve injury through microfluidic devices

Traumatic injuries, both in the central nervous system (CNS) and peripheral nervous system (PNS), can potentially lead to irreversible damage resulting in permanent loss of function. Investigating the complex dynamics involved in these processes may elucidate the biological mechanisms of both nerve degeneration and regeneration, and may potentially lead to the development of new therapies for recovery. A scientific overview on the biological foundations of nerve injury is presented. Differences between nerve regeneration in the central and PNS are discussed. Advances in microtechnology over the past several years have led to the development of invaluable tools that now facilitate investigation of neurobiology at the cellular scale. Microfluidic devices are explored as a means to study nerve injury at the necessary simplification of the cellular level, including those devices aimed at both chemical and physical injury, as well as those that recreate the post-injury environment.

Biofunctionalisation of electrically conducting polymers

During a single decade of research, evidence has emerged that glial scar formation around the electro-tissue interface drives neural loss and increases the signal impedance of the electrodes, compromising the efficiency of the stimulating systems. Studies with conducting polymers (CPs) as electrode coatings have shown enhanced tissue integration and electrode performance in situ through biochemical and physicomechanical functionalisation. In this review, recent findings on CP modifications are provided in the context of neurospecific biomaterials, shedding light on the valuable impact of multifunctionalised strategies for biomedical applications.