Carbohydrate based biomaterials for neural interface applications

Unraveling the intricacies of glycosaminoglycan biosynthesis: Decoding the molecular symphony in understanding complex polysaccharide assembly

Glycosaminoglycans (GAGs) are extensively utilized in clinical, cosmetic, and healthcare field, as well as in the treatment of thrombosis, osteoarthritis, rheumatism, and cancer. The biological production of GAGs is a strategy that has garnered significant attention due to its numerous advantages over traditional preparation methods. In this review, we embark on a journey to decode the intricate molecular symphony that orchestrates the biosynthesis of glycosaminoglycans. By unraveling the complex interplay of related enzymes and thorough excavation of the intricate metabolic cascades involved, GAGs chain aggregation and transportation, which efficiently and controllably modulate GAGs sulfation patterns involved in biosynthetic pathway, we endeavor to offer a thorough comprehension of how these remarkable GAGs are intricately assembled and pushes the boundaries of our understanding in GAGs biosynthesis.

Investigation of a chondroitin sulfate-based bioactive coating for neural interface applications

Invasive neural implants allow for high-resolution bidirectional communication with the nervous tissue and have demonstrated the ability to record neural activity, stimulate neurons, and sense neurochemical species with high spatial selectivity and resolution. However, upon implantation, they are exposed to a foreign body response which can disrupt the seamless integration of the device with the native tissue and lead to deterioration in device functionality for chronic implantation. Modifying the device surface by incorporating bioactive coatings has been a promising approach to camouflage the device and improve integration while maintaining device performance. In this work, we explored the novel application of a chondroitin sulfate (CS) based hydrophilic coating, with anti-fouling and neurite-growth promoting properties for neural recording electrodes. CS-coated samples exhibited significantly reduced protein-fouling in vitro which was maintained for up to 4-weeks. Cell culture studies revealed a significant increase in neurite attachment and outgrowth and a significant decrease in microglia attachment and activation for the CS group as compared to the control. After 1-week of in vivo implantation in the mouse cortex, the coated probes demonstrated significantly lower biofouling as compared to uncoated controls. Like the in vitro results, increased neuronal population (neuronal nuclei and neurofilament) and decreased microglial activation were observed. To assess the coating's effect on the recording performance of silicon microelectrodes, we implanted coated and uncoated electrodes in the mouse striatum for 1 week and performed impedance and recording measurements. We observed significantly lower impedance in the coated group, likely due to the increased wettability of the coated surface. The peak-to-peak amplitude and the noise floor levels were both lower in the CS group compared to the controls, which led to a comparable signal-to-noise ratio between the two groups. The overall single unit yield (% channels recording a single unit) was 74% for the CS and 67% for the control group on day 1. Taken together, this study demonstrates the effectiveness of the polysaccharide-based coating in reducing biofouling and improving biocompatibility for neural electrode devices.

3D Printing of Polysaccharide-Based Hydrogel Scaffolds for Tissue Engineering Applications: A Review

In tissue engineering, 3D printing represents a versatile technology employing inks to construct three-dimensional living structures, mimicking natural biological systems. This technology efficiently translates digital blueprints into highly reproducible 3D objects. Recent advances have expanded 3D printing applications, allowing for the fabrication of diverse anatomical components, including engineered functional tissues and organs. The development of printable inks, which incorporate macromolecules, enzymes, cells, and growth factors, is advancing with the aim of restoring damaged tissues and organs. Polysaccharides, recognized for their intrinsic resemblance to components of the extracellular matrix have garnered significant attention in the field of tissue engineering. This review explores diverse 3D printing techniques, outlining distinctive features that should characterize scaffolds used as ideal matrices in tissue engineering. A detailed investigation into the properties and roles of polysaccharides in tissue engineering is highlighted. The review also culminates in a profound exploration of 3D polysaccharide-based hydrogel applications, focusing on recent breakthroughs in regenerating different tissues such as skin, bone, cartilage, heart, nerve, vasculature, and skeletal muscle. It further addresses challenges and prospective directions in 3D printing hydrogels based on polysaccharides, paving the way for innovative research to fabricate functional tissues, enhancing patient care, and improving quality of life.

Polysaccharides as a promising platform for the treatment of spinal cord injury: A review

Spinal cord injury is incurable and often results in irreversible damage to motor function and autonomic sensory abilities. To enhance the effectiveness of therapeutic substances such as cells, growth factors, drugs, and nucleic acids for treating spinal cord injuries, as well as to reduce the toxic side effects of chemical reagents, polysaccharides have been gained attention due to their immunomodulatory properties and the biocompatibility and biodegradability of polysaccharide scaffolds. Polysaccharides hold potential as drug delivery systems in treating spinal cord injuries. This article aims to present an extensive evaluation of the potential applications of polysaccharide materials in scaffold construction, drug delivery, and immunomodulation over the past five years so that offering new directions and opportunities for the treatment of spinal cord injuries.

Advances in electrode interface materials and modification technologies for brain-computer interfaces

Recent advances in neuroelectrode interface materials and modification technologies are reviewed. Brain-computer interface is the new method of human-computer interaction, which not only can realise the exchange of information between the human brain and external devices, but also provides a brand-new means for the diagnosis and treatment of brain-related diseases. The neural electrode interface part of brain-computer interface is an important area for electrical, optical and chemical signal transmission between brain tissue system and external electronic devices, which determines the performance of brain-computer interface. In order to solve the problems of insufficient flexibility, insufficient signal recognition ability and insufficient biocompatibility of traditional rigid electrodes, researchers have carried out extensive studies on the neuroelectrode interface in terms of materials and modification techniques. This paper introduces the biological reactions that occur in neuroelectrodes after implantation into brain tissue and the decisive role of the electrode interface for electrode function. Following this, the latest research progress on neuroelectrode materials and interface materials is reviewed from the aspects of neuroelectrode materials and modification technologies, firstly taking materials as a clue, and then focusing on the preparation process of neuroelectrode coatings and the design scheme of functionalised structures.

Conducting polymer-based nanostructured materials for brain-machine interfaces

As scientists discovered that raw neurological signals could translate into bioelectric information, brain-machine interfaces (BMI) for experimental and clinical studies have experienced massive growth. Developing suitable materials for bioelectronic devices to be used for real-time recording and data digitalizing has three important necessitates which should be covered. Biocompatibility, electrical conductivity, and having mechanical properties similar to soft brain tissue to decrease mechanical mismatch should be adopted for all materials. In this review, inorganic nanoparticles and intrinsically conducting polymers are discussed to impart electrical conductivity to systems, where soft materials such as hydrogels can offer reliable mechanical properties and a biocompatible substrate. Interpenetrating hydrogel networks offer more mechanical stability and provide a path for incorporating polymers with desired properties into one strong network. Promising fabrication methods, like electrospinning and additive manufacturing, allow scientists to customize designs for each application and reach the maximum potential for the system. In the near future, it is desired to fabricate biohybrid conducting polymer-based interfaces loaded with cells, giving the opportunity for simultaneous stimulation and regeneration. Developing multi-modal BMIs, Using artificial intelligence and machine learning to design advanced materials are among the future goals for this field. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease.

Preparation and Characterization of Hydrogel Films and Nanoparticles Based on Low-Esterified Pectin for Anticancer Applications

Prospective adjuvant anticancer therapy development includes the establishing of drug delivery systems based on biocompatible and biodegradable carriers. We have designed films and nanoparticles (NPs) based on low-esterified pectin hydrogel using the ionic gelation method. We investigated morphology, nanomechanical properties, biocompatibility and anticancer activity. Hydrogel films are characterized by tunable viscoelastic properties and surface nanoarchitectonics through pectin concentration and esterification degree (DE), expressed in variable pore frequency and diameter. An in vitro study showed a significant reduction in metabolic activity and the proliferation of the U87MG human glioblastoma cell line, probably affected via the adhesion mechanism. Glioma cells formed neurosphere-like conglomerates with a small number of neurites when cultured on fully de-esterified pectin films and they did not produce neurites on the films prepared on 50% esterified pectin. Pectin NPs were examined in terms of size distribution and nanomechanical properties. The NPs' shapes were proved spherical with a mean diameter varying in the range of 90-115 nm, and a negative zeta potential from -8.30 to -7.86 mV, which indicated their stability. The NPs did not demonstrate toxic effect on cells or metabolism inhibition, indicating good biocompatibility. Nanostructured biomaterials prepared on low-esterified pectins could be of interest for biomedical applications in adjuvant anticancer therapy and for designing drug delivery systems.

Streamlining the interface between electronics and neural systems for bidirectional electrochemical communication

Seamless neural interfaces conjoining neurons and electrochemical devices hold great potential for highly efficient signal transmission across neural systems and the external world. Signal transmission through chemical sensing and stimulation via electrochemistry is remarkable because communication occurs through the same chemical language of neurons. Emerging strategies based on synaptic interfaces, iontronics-based neuromodulation, and improvements in selective neurosensing techniques have been explored to achieve seamless integration and efficient neuro-electronics communication. Synaptic interfaces can directly exchange signals to and from neurons, in a similar manner to that of chemical synapses. Hydrogel-based iontronic chemical delivery devices are operationally compatible with neural systems for improved neuromodulation. In this perspective, we explore developments to improve the interface between neurons and electrodes by targeting neurons or sub-neuronal regions including synapses. Furthermore, recent progress in electrochemical neurosensing and iontronics-based chemical delivery is examined.

Flexible IrOx neural electrode for mouse vagus nerve stimulation

Vagus nerve stimulation (VNS) is being actively explored as a treatment for multiple conditions as part of bioelectronic medicine research. Reliable and safe VNS in mouse models is a critical need for understanding mechanisms of these. We report on the development and evaluation of a microfabricated cuff electrode (MouseFlex) constructed of polyimide (PI) and with iridium oxide (IrOx) electrodes that is thermoformed to 86 µm ± 12 µm radius to interface the mouse cervical vagus nerve (r ≈ 50 µm). Innovative bench-top methods were used to evaluate the stimulation stability and electrochemical properties of electrodes. Our aggressive stimulation stability (Stim-Stab) test utilized 1 billion pulses at a 1000 Hz with a current density of 6.28 A/cm2 (1.51 mC/cm2/phase) delivering 3023 × 103 C/cm2 to evaluate electrode lifetimes, and all electrodes remained functional. We also investigated the effects of thermoforming on their impedance, charge storage capacity (CSC), and charge injection capacity (CIC). The modest changes in electrochemical properties indicate that the thermoforming process was well tolerated. Thermoformed electrode safety and efficacy were evaluated in-vivo by performing acute VNS in mice and monitoring their heart and respiration rate as biomarkers. Their electrochemical properties were also measured before, during and after VNS. Bradycardia and bradypnea were reliably induced at stimulation currents of 100 to 200 µA, well below the in-vivo CIC of ∼1250 µA (∼0.5 mC/cm2), supporting their safety and efficacy. The electrode impedance increased and CIC decreased during in-vivo use, but largely reversed these changes in in-vitro testing after enzymatic cleaning, supporting their tolerance for surgical use. STATEMENT OF SIGNIFICANCE: Vagus nerve stimulation (VNS) is a rapidly growing aspect of healthcare and bioelectronic medicine research. Reliable and safe VNS in mice with small diameter (d ≈ 100 µm) nerves has been a challenge due to achieving intimate contact with the nerve, and the stimulation stability of commonly used electrodes. We demonstrate a microfabricated (MouseFlex) cuff electrode constructed of polyimide with IrOx electrodes that is thermoformed to contact the mouse cervical vagus. Bench studies highlight the stimulation stability exceeded 109 pulses at 6.28 A/cm2 and their electrochemical properties were measured before, during, and after bench and nerve stimulation. Nerve stimulation induced bradycardia and bradypnea at currents below the in-vivo charge injection capacity, supporting their safety, efficacy, and tolerance for surgical handling.