Advances in 3D tissue models for neural engineering: self-assembled engineered tissue models.

Neural tissue engineering has emerged as a promising field that aims to create functional neural tissue for therapeutic applications, drug screening, and disease modelling. It is becoming evident in the literature that this goal requires development of three-dimensional (3D) constructs that can mimic the complex microenvironment of native neural tissue, including its biochemical, mechanical, physical, and electrical properties. These 3D models can be broadly classified as self-assembled models, which include spheroids, organoids, and assembloids, and engineered models, such as those based on decellularized or polymeric scaffolds.

Deciphering platinum dissolution in neural stimulation electrodes: Electrochemistry or biology?

Platinum (Pt) is the metal of choice for electrodes in implantable neural prostheses like the cochlear implants, deep brain stimulating devices, and brain-computer interfacing technologies. However, it is well known since the 1970s that Pt dissolution occurs with electrical stimulation. More recent clinical and in vivo studies have shown signs of corrosion in explanted electrode arrays and the presence of Pt-containing particulates in tissue samples.

Bioelectronic Neural Interfaces: Improving Neuromodulation Through Organic Conductive Coatings.

Integration of bioelectronic devices in clinical practice is expanding rapidly, focusing on conditions ranging from sensory to neurological and mental health disorders. While platinum (Pt) electrodes in neuromodulation devices such as cochlear implants and deep brain stimulators have shown promising results, challenges still affect their long-term performance. Key among these are electrode and device longevity in vivo, and formation of encapsulating fibrous tissue.

Effect of Hydrogel-based Model Fibrosis on Electrical Properties of Bioelectrodes.

Fibrous tissue encapsulation can impact the performance of bioelectrodes following implantation. For example, significant increases in electrode impedance can occur within four weeks post-implantation. A key limitation hindering the understanding of host response-mediated impedance change is the reliance on animal models or complex in vitro cell cultures for electrode testing.

Growing human-scale scala tympani-likecell constructs.

Emerging materials and electrode technologies have potential to revolutionise development of higher resolution next-generation, bionic devices. However, barriers associated with the extended timescales, regulatory constraints, and opportunity costs of preclinical and clinical studies, can inhibit such innovation. Development ofmodels that mimic human tissues would provide an enabling platform to overcome many of these barriers in the product development pathway.

Improving Deep Brain Stimulation Electrode Performance Through Use of Conductive Hydrogel Coatings.

Active implantable neurological devices like deep brain stimulators have been used over the past few decades to treat movement disorders such as those in people with Parkinson's disease and more recently, in psychiatric conditions like obsessive compulsive disorder. Electrode-tissue interfaces that support safe and effective targeting of specific brain regions are critical to success of these devices. Development of directional electrodes that activate smaller volumes of brain tissue requires electrodes to operate safely with higher charge densities.

Challenges and solutions for fabrication of three-dimensional cocultures of neural cell-loaded biomimetic constructs.

Fabrication of three-dimensional (3D) constructs to model body tissues and organs can contribute to research into tissue development and models for studying disease, as well as supporting preclinical drug screening in vitro. Furthermore, 3D constructs can also be used for diagnosis and therapy of disease conditions via lab on a chip and microarrays for diagnosis and engineered products for tissue repair, replacement, and regeneration. While cell culture approaches for studying tissue development and disease in two dimensions are long-established, the translation of this knowledge into 3D environments remains a fertile field of research.

Subthreshold Electrical Stimulation for Controlling Protein-Mediated Impedance Increases in Platinum Cochlear Electrode.

Objective: This study evaluated subthreshold biphasic stimulation pulses as a strategy to stabilize electrode impedance via control of protein adsorption. Following implantation, cochlear electrodes undergo impedance fluctuations thought to be caused by protein adsorption and/or inflammatory responses. Impedance increases can impact device power consumption, safe charge injection limits, and long-term stability of electrodes.

Ambient-Temperature Waterborne Polymer/rGO Nanocomposite Films: Effect of rGO Distribution on Electrical Conductivity.

Electrically conductive polymer/rGO (reduced graphene oxide) films based on styrene and -butyl acrylate are prepared by a variety of aqueous latex based routes involving ambient temperature film formation. Techniques based on miniemulsion polymerization using GO as surfactant and "physical mixing" approaches (i.e.

Electrochemical and mechanical performance of reduced graphene oxide, conductive hydrogel, and electrodeposited Pt-Ir coated electrodes: an active in vitro study.

Objective: To systematically compare the in vitro electrochemical and mechanical properties of several electrode coatings that have been reported to increase the efficacy of medical bionics devices by increasing the amount of charge that can be delivered safely to the target neural tissue.

Approach: Smooth platinum (Pt) ring and disc electrodes were coated with reduced graphene oxide, conductive hydrogel, or electrodeposited Pt-Ir. Electrodes with coatings were compared with uncoated smooth Pt electrodes before and after an in vitro accelerated aging protocol.

Conductive elastomer composites for fully polymeric, flexible bioelectronics.

Flexible polymeric bioelectronics have the potential to address the limitations of metallic electrode arrays by minimizing the mechanical mismatch at the device-tissue interface for neuroprosthetic applications. This work demonstrates the straightforward fabrication of fully organic electrode arrays based on conductive elastomers (CEs) as a soft, flexible and stretchable electroactive composite material. CEs were designed as hybrids of polyurethane elastomers (PU) and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), with the aim of combining the electrical properties of PEDOT:PSS with the mechanical compliance of elastomers.

Tissue engineered hydrogels supporting 3D neural networks.

Promoting nerve regeneration requires engineering cellular carriers to physically and biochemically support neuronal growth into a long lasting functional tissue. This study systematically evaluated the capacity of a biosynthetic poly(vinyl alcohol) (PVA) hydrogel to support growth and differentiation of co-encapsulated neurons and glia. A significant challenge is to understand the role of the dynamic degradable hydrogel mechanical properties on expression of relevant cellular morphologies and function.

Stimulation of peripheral nerves using conductive hydrogel electrodes.

Nerve block via electrical stimulation of nerves requires a device capable of transferring large amounts of charge across the neural interface on chronic time scales. Current metal electrode designs are limited in their ability to safely and effectively deliver this charge in a stable manner. Conductive hydrogel (CH) coatings are a promising alternative to metal electrodes for neural interfacing devices.

Cytotoxic Activity of a Black Bean (Phaseolus vulgaris L.) Extract and its Flavonoid Fraction in Both In Vitro and In Vivo Models of Lymphoma.

Background: Black bean (Phaseolus vulgaris L.) is a very common legume seed in Mexican diet. Flavonoids and crude extracts from different plants have been reported as effective agents for chemoprevention and cytotoxicity in several cancer cell lines.

Visual Prosthesis: Interfacing Stimulating Electrodes with Retinal Neurons to Restore Vision.

The bypassing of degenerated photoreceptors using retinal neurostimulators is helping the blind to recover functional vision. Researchers are investigating new ways to improve visual percepts elicited by these means as the vision produced by these early devices remain rudimentary. However, several factors are hampering the progression of bionic technologies: the charge injection limits of metallic electrodes, the mechanical mismatch between excitable tissue and the stimulating elements, neural and electric crosstalk, the physical size of the implanted devices, and the inability to selectively activate different types of retinal neurons.

Producing 3D neuronal networks in hydrogels for living bionic device interfaces.

Hydrogels hold significant promise for supporting cell based therapies in the field of bioelectrodes. It has been proposed that tissue engineering principles can be used to improve the integration of neural interfacing electrodes. Degradable hydrogels based on poly (vinyl alcohol) functionalised with tyramine (PVA-Tyr) have been shown to support covalent incorporation of non-modified tyrosine rich proteins within synthetic hydrogels.

Organic electrode coatings for next-generation neural interfaces.

Traditional neuronal interfaces utilize metallic electrodes which in recent years have reached a plateau in terms of the ability to provide safe stimulation at high resolution or rather with high densities of microelectrodes with improved spatial selectivity. To achieve higher resolution it has become clear that reducing the size of electrodes is required to enable higher electrode counts from the implant device. The limitations of interfacing electrodes including low charge injection limits, mechanical mismatch and foreign body response can be addressed through the use of organic electrode coatings which typically provide a softer, more roughened surface to enable both improved charge transfer and lower mechanical mismatch with neural tissue.