Nanotechnology-Based Approaches for Guiding Neural Regeneration

Palladium-reduced graphene oxide nanocomposites enhance neurite outgrowth and protect neurons from Ishemic stroke

Currently, the construction of novel biomimetic reduced graphene oxide (RGO)-based nanocomposites to induce neurite sprouting and repair the injured neurons represents a promising strategy in promoting neuronal development or treatment of cerebral anoxia or ischemia. Here, we present an effective method for constructing palladium-reduced graphene oxide (Pd-RGO) nanocomposites by covalently bonding Pd onto RGO surfaces to enhance neurite sprouting of cultured neurons. As described, the Pd-RGO nanocomposites exhibit the required physicochemical features for better biocompatibility without impacting cell viability. Primary neurons cultured on Pd-RGO nanocomposites had significantly increased number and length of neuronal processes, including both axons and dendrites, compared with the control. Western blotting showed that Pd-RGO nanocomposites improved the expression levels of growth associate protein-43 (GAP-43), as well as β-III tubulin, Tau-1, microtubule-associated protein-2 (MAP2), four proteins that are involved in regulating neurite sprouting and outgrowth. Importantly, Pd-RGO significantly promoted neurite length and complexity under oxygen-glucose deprivation/re-oxygenation (OGD/R) conditions, an in vitro cellular model of ischemic brain damage, that closely relates to neuronal GAP-43 expression. Furthermore, using the middle cerebral artery occlusion (MCAO) model in rats, we found Pd-RGO effectively reduced the infarct area, decreased neuronal apoptosis in the brain, and improved the rats' behavioral outcomes after MCAO. Together, these results indicate the great potential of Pd-RGO nanocomposites as a novel excellent biomimetic material for neural interfacing that shed light on its applications in brain injuries.

Nanotherapeutics for Alleviating Anesthesia-Associated Complications

Current management of anesthesia-associated complications falls short in terms of both efficacy and safety. Nanomaterials with versatile properties and unique nano-bio interactions hold substantial promise as therapeutics for addressing these complications. This review conducts a thorough examination of the existing nanotherapeutics and highlights the strategies for developing prospective nanomedicines to mitigate anesthetics-related toxicity. Initially, general, regional, and local anesthesia along with the commonly used anesthetics and related prevalent side effects are introduced. Furthermore, employing nanotechnology to prevent and alleviate the complications of anesthetics is systematically demonstrated from three aspects, that is, developing 1) safe nano-formulization for anesthetics; 2) nano-antidotes to sequester overdosed anesthetics and alter their pharmacokinetics; 3) nanomedicines with pharmacodynamic activities to treat anesthetics toxicity. Finally, the prospects and challenges facing the clinical translation of nanotherapeutics for anesthesia-related complications are discussed. This work provides a comprehensive roadmap for developing effective nanotherapeutics to prevent and mitigate anesthesia-associated toxicity, which can potentially revolutionize the management of anesthesia complications.

Novel Approaches to Studying SLC13A5 Disease

The role of the sodium citrate transporter (NaCT) SLC13A5 is multifaceted and context-dependent. While aberrant dysfunction leads to neonatal epilepsy, its therapeutic inhibition protects against metabolic disease. Notably, insights regarding the cellular and molecular mechanisms underlying these phenomena are limited due to the intricacy and complexity of the latent human physiology, which is poorly captured by existing animal models. This review explores innovative technologies aimed at bridging such a knowledge gap. First, I provide an overview of SLC13A5 variants in the context of human disease and the specific cell types where the expression of the transporter has been observed. Next, I discuss current technologies for generating patient-specific induced pluripotent stem cells (iPSCs) and their inherent advantages and limitations, followed by a summary of the methods for differentiating iPSCs into neurons, hepatocytes, and organoids. Finally, I explore the relevance of these cellular models as platforms for delving into the intricate molecular and cellular mechanisms underlying SLC13A5-related disorders.

Electro-conductive chitosan/graphene bio-nanocomposite scaffold for tissue engineering of the central nervous system

Degenerative central nervous system (CNS) disorders and traumatic brain injuries are common nowadays. These may induce the loss of neuronal cells and delicate connections essential for optimal CNS function. The CNS tissue has restricted regeneration ability, hindering the development of effective therapies. Developing cell and tissue instructive materials may bring up new treatment possibilities. In this study, chitosan-graphene nano platelets (GNPs) composite films were developed to regenerate brain cells. This study evaluates the effects of GNP concentration (0.5, 1 and 2 wt%) and their alignment on mechanical, electrical, surface, protein adsorption and biological properties of the regenerative scaffolds. Incorporating and aligning GNPs into chitosan matrix improved all the physical and biological properties. On reinforced scaffolds, HT22 cell morphology mimics pyramidal brain cells, which are responsible for the brain's highly branched neural network. Additionally, the reinforced scaffolds supported Mesenchymal Stem like Cells growth and were biocompatible in vivo. The alignment of GNPs in the chitosan matrix offered the appropriate physicochemical and biological properties to promote adhesion, proliferation and shape morphogenesis of hippocampal HT22 neuronal cells. Overall, this study delineates the enormous potential offered by the GNP-reinforced scaffolds for regeneration of central nervous system, especially the brain.

Supramolecular assemblies with spatio-temporal sequential drug delivery capability treat spinal cord injury via neuroprotection and immunoregulation

Spinal cord injury (SCI) can result in irreversible motor and sensory deficits. However, up to data, clinical first-line drugs have ambiguous benefits and debilitating side effects, mainly due to the insufficient accumulation, poor physiological barrier penetration, and lack of spatio-temporal controlled release at lesion tissue. Herein, we proposed a supramolecular assemblies composed of hyperbranched polymer-formed core/shell structure through host-guest interactions. Such HPAA-BM@CD-HPG-C assemblies co-loaded with p38 inhibitor (SB203580) and insulin-like growth factor 1(IGF-1) are able to achieve time- and space-programmed sequential delivery benefiting from their cascaded responsiveness. The core-shell disassembly of HPAA-BM@CD-HPG-C occurs in acidic micro-environment around lesion, achieving preferentially the burst release of IGF-1 to protect survival neurons. Subsequently, the HPAA-BM cores containing SB203580 are endocytosed by the recruited macrophages and degraded by intracellular GSH, accelerating the release of SB203580 to promote the conversion from M1 to M2 macrophage. Hence, the successive synergy of neuroprotection and immunoregulation effects contribute to subsequent nerve repair and locomotor recovery as demonstrated in vitro and in vivo studies. Thus, our fabrication provides a strategy that multiple drugs co-delivery in a spatio-temporal selective manner adapting to the disease progression through self-cascaded disintegration, are expected to realize multidimensional precise treatment of SCI.

Nanoparticles-mediated ion channels manipulation: From their membrane interactions to bioapplications

Ion channels are transmembrane proteins ubiquitously expressed in all cells that control various ions (e.g. Na⁺, K⁺, Ca²⁺ and Cl^- etc) crossing cellular plasma membrane, which play critical roles in physiological processes including regulating signal transduction, cell proliferation as well as excitatory cell excitation and conduction. Abnormal ion channel function is usually associated with dysfunctions and many diseases, such as neurodegenerative disorders, ophthalmic diseases, pulmonary diseases and even cancers. The precise regulation of ion channels not only helps to decipher physiological and pathological processes, but also is expected to become cutting-edge means for disease treatment. Recently, nanoparticles-mediated ion channel manipulation emerges as a highly promising way to meet the increasing requirements with respect to their simple, efficient, precise, spatiotemporally controllable and non-invasive regulation in biomedicine and other research frontiers. Thanks the advantages of their unique properties, nanoparticles can not only directly block the pore sites or kinetics of ion channels through their tiny size effect, and perturb active voltage-gated ion channel by their charged surface, but they can also act as antennas to conduct or enhance external physical stimuli to achieve spatiotemporal, precise and efficient regulation of various ion channel activities (e.g. light-, mechanical-, and temperature-gated ion channels etc). So far, nanoparticles-mediated ion channel regulation has shown potential prospects in many biomedical fields at the interfaces of neuro- and cardiovascular modulation, physiological function regeneration and tumor therapy et al. Towards such important fields, in this typical review, we specifically outline the latest studies of different types of ion channels and their activities relevant to the diseases. In addition, the different types of stimulation responsive nanoparticles, their interaction modes and targeting strategies towards the plasma membrane ion channels will be systematically summarized. More importantly, the ion channel regulatory methods mediated by functional nanoparticles and their bioapplications associated with physiological modulation and therapeutic development will be discussed. Last but not least, current challenges and future perspectives in this field will be covered as well.

Magnetic Nanobubble Mechanical Stress Induces the Piezo1-Ca2+ -BMP2/Smad Pathway to Modulate Neural Stem Cell Fate and MRI/Ultrasound Dual Imaging Surveillance for Ischemic Stroke

Neural stem cells (NSCs) are used to treat various nervous system diseases because of their self-renewal ability and multidirectional differentiation potential. However, an insufficient ability to track their migration in vivo and poor control over their survival and differentiation efficiency are two major critical challenges for clinical application. Here, it is shown that when magnetic nanobubbles (MNBs), which are assembled from magnetic nanoparticles, are internalized by NSCs, intramembrane volumetric oscillation of the MNBs induces an increase in intracellular hydrostatic pressure and cytoskeleton force, resulting in the activation of the Piezo1-Ca²⁺ mechanosensory channel. This subsequently triggers the BMP2/Smad biochemical signaling pathway, leading to differentiation of NSCs into the neuronal phenotype. Signaling through the Piezo1-Ca²⁺ -BMP2/Smad pathway can be further accelerated by application of an external shear stress force using low-intensity pulsed ultrasound. More importantly, magnetic resonance imaging and ultrasound imaging surveillance of NSCs based on MNB labeling can be leveraged to provide NSC therapeutic outcomes. Both the in vitro and in vivo findings demonstrate that a bubble nanostructure-induced physical force can modulate and control the mechanical signaling pathway regulating stem cell development.

Gold nanostructures: synthesis, properties, and neurological applications

Recent advances in technology are expected to increase our current understanding of neuroscience. Nanotechnology and nanomaterials can alter and control neural functionality in both in vitro and in vivo experimental setups. The intersection between neuroscience and nanoscience may generate long-term neural interfaces adapted at the molecular level. Owing to their intrinsic physicochemical characteristics, gold nanostructures (GNSs) have received much attention in neuroscience, especially for combined diagnostic and therapeutic (theragnostic) purposes. GNSs have been successfully employed to stimulate and monitor neurophysiological signals. Hence, GNSs could provide a promising solution for the regeneration and recovery of neural tissue, novel neuroprotective strategies, and integrated implantable materials. This review covers the broad range of neurological applications of GNS-based materials to improve clinical diagnosis and therapy. Sub-topics include neurotoxicity, targeted delivery of therapeutics to the central nervous system (CNS), neurochemical sensing, neuromodulation, neuroimaging, neurotherapy, tissue engineering, and neural regeneration. It focuses on core concepts of GNSs in neurology, to circumvent the limitations and significant obstacles of innovative approaches in neurobiology and neurochemistry, including theragnostics. We will discuss recent advances in the use of GNSs to overcome current bottlenecks and tackle technical and conceptual challenges.

Tin oxide nanoparticles trigger the formation of amyloid β oligomers/protofibrils and underlying neurotoxicity as a marker of Alzheimer's diseases

Alzheimer's disease (AD) is known as one of the most common forms of dementia, and oligomerization of amyloid β (Aβ₄₂) peptides can result in the onset of AD. Tin oxide nanoparticles (SnO₂ NPs) showed several applications in biomedical fields can trigger unwanted interaction with proteins and inducing protein aggregation. Herein, we synthesized SnO₂ NPs via the hydrothermal method and characterized by UV-visible, XRD, FTIR, TEM, and DLS techniques. Afterward, the formation of Aβ₄₂ amyloid oligomers/protofibrils treated alone and with SnO₂ NPs was explored by ThT and Nile red fluorescence and CD spectroscopic methods along with TEM imaging. The neurotoxicity of different spices of Aβ₄₂ samples against PC-12 cells was then explored by MTT and caspase-3 activity assays. The characterization of SnO₂ NPs confirmed the successful synthesis of crystalline NPs (20-30 nm). Different biophysical and cellular analyses indicated that SnO₂ NPs accelerated Aβ₄₂ fibrillogenesis and promoted amyloid oligomers/protofibrils cytotoxicity. As compared to the Aβ₄₂ samples grown alone, the ThT and ANS fluorescence intensity along with ellipticity results indicated the promotory effect of SnO₂ NPs on the formation of oligomers/protofibrils. Also, the cellular results showed that the treated Aβ₄₂ samples with SnO₂ NPs further reduced cell viability through activation of caspase-3. In conclusion, SnO₂ NPs greatly accelerate the fibrillation of Aβ₄₂ peptides and lead to the formation of more toxic species. The present data may offer further warrants into nano-based systems for biomedical applications in the central nervous system.

Effects of nanofibers on mesenchymal stem cells: environmental factors affecting cell adhesion and osteogenic differentiation and their mechanisms

Nanofibers can mimic natural tissue structure by creating a more suitable environment for cells to grow, prompting a wide application of nanofiber materials. In this review, we include relevant studies and characterize the effect of nanofibers on mesenchymal stem cells, as well as factors that affect cell adhesion and osteogenic differentiation. We hypothesize that the process of bone regeneration in vitro is similar to bone formation and healing in vivo, and the closer nanofibers or nanofibrous scaffolds are to natural bone tissue, the better the bone regeneration process will be. In general, cells cultured on nanofibers have a similar gene expression pattern and osteogenic behavior as cells induced by osteogenic supplements in vitro. Genes involved in cell adhesion (focal adhesion kinase (FAK)), cytoskeletal organization, and osteogenic pathways (transforming growth factor-β (TGF-β)/bone morphogenic protein (BMP), mitogen-activated protein kinase (MAPK), and Wnt) are upregulated successively. Cell adhesion and osteogenesis may be influenced by several factors. Nanofibers possess certain physical properties including favorable hydrophilicity, porosity, and swelling properties that promote cell adhesion and growth. Moreover, nanofiber stiffness plays a vital role in cell fate, as cell recruitment for osteogenesis tends to be better on stiffer scaffolds, with associated signaling pathways of integrin and Yes-associated protein (YAP)/transcriptional co-activator with PDZ-binding motif (TAZ). Also, hierarchically aligned nanofibers, as well as their combination with functional additives (growth factors, HA particles, etc.), contribute to osteogenesis and bone regeneration. In summary, previous studies have indicated that upon sensing the stiffness of the nanofibrous environment as well as its other characteristics, stem cells change their shape and tension accordingly, regulating downstream pathways followed by adhesion to nanofibers to contribute to osteogenesis. However, additional experiments are needed to identify major signaling pathways in the bone regeneration process, and also to fully investigate its supportive role in fabricating or designing the optimum tissue-mimicking nanofibrous scaffolds.

Recent Advances in the Application of Two-Dimensional Nanomaterials for Neural Tissue Engineering and Regeneration

The complexity of the nervous system structure and function, and its slow regeneration rate, makes it more difficult to treat compared to other tissues in the human body when an injury occurs. Moreover, the current therapeutic approaches including the use of autografts, allografts, and pharmacological agents have several drawbacks and can not fully restore nervous system injuries. Recently, nanotechnology and tissue engineering approaches have attracted many researchers to guide tissue regeneration in an effective manner. Owing to their remarkable physicochemical and biological properties, two-dimensional (2D) nanomaterials have been extensively studied in the tissue engineering and regenerative medicine field. The great conductivity of these materials makes them a promising candidate for the development of novel scaffolds for neural tissue engineering application. Moreover, the high loading capacity of 2D nanomaterials also has attracted many researchers to utilize them as a drug/gene delivery method to treat various devastating nervous system disorders. This review will first introduce the fundamental physicochemical properties of 2D nanomaterials used in biomedicine and the supporting biological properties of 2D nanomaterials for inducing neuroregeneration, including their biocompatibility on neural cells, the ability to promote the neural differentiation of stem cells, and their immunomodulatory properties which are beneficial for alleviating chronic inflammation at the site of the nervous system injury. It also discusses various types of 2D nanomaterials-based scaffolds for neural tissue engineering applications. Then, the latest progress on the use of 2D nanomaterials for nervous system disorder treatment is summarized. Finally, a discussion of the challenges and prospects of 2D nanomaterials-based applications in neural tissue engineering is provided.

Control the Neural Stem Cell Fate with Biohybrid Piezoelectrical Magnetite Micromotors

Inducing neural stem cells to differentiate and replace degenerated functional neurons represents the most promising approach for neural degenerative diseases including Parkinson's disease, Alzheimer's disease, etc. While diverse strategies have been proposed in recent years, most of these are hindered due to uncontrollable cell fate and device invasiveness. Here, we report a minimally invasive micromotor platform with biodegradable helical Spirulina plantensis (S. platensis) as the framework and superparamagnetic Fe₃O₄ nanoparticles/piezoelectric BaTiO₃ nanoparticles as the built-in function units. With a low-strength rotational magnetic field, this integrated micromotor system can perform precise navigation in biofluid and achieve single-neural stem cell targeting. Remarkably, by tuning ultrasound intensity, thus the local electrical output by the motor, directed differentiation of the neural stem cell into astrocytes, functional neurons (dopamine neurons, cholinergic neurons), and oligodendrocytes, can be achieved. This micromotor platform can serve as a highly controllable wireless tool for bioelectronics and neuronal regenerative therapy.

Tetrahedral DNA nanostructures functionalized by multivalent microRNA132 antisense oligonucleotides promote the differentiation of mouse embryonic stem cells into dopaminergic neurons

MicroRNA132 (miR132) negatively regulates the differentiation of mouse embryonic stem cells (ESCs) into dopaminergic (DAergic) neurons; in contrast, antisense oligonucleotide against miR132 (miR132-ASO) effectively blocks the activity of endogenous miR132 and thereafter promotes the differentiation of DAergic neurons. However, it is difficult for miR132-ASO to enter cells without a suitable delivery system. Tetrahedral DNA nanostructures (TDNs), as a new type of DNA-based nanocarrier, have great potential in biomedical applications and even have been reported to promote stem cell differentiation. In this study, we developed functional multivalent DNA nanostructures by appending miR132-ASO motifs to three-dimensional TDNs (miR132-ASO-TDNs). Our data clearly revealed that miR132-ASO-TDNs exposure can promote the differentiation of ESCs into DAergic neurons as well as elevate DA release from differentiated DAergic neurons. MiR132-ASO-TDNs could serve as a novel biofunctional nanomaterial to improve the efficiency of DAergic neurons differentiation. Our findings may also provide a new approach for stem cell therapy against neurodegenerative diseases.

Light-Responsive Inorganic Biomaterials for Biomedical Applications

Light-responsive inorganic biomaterials are an emerging class of materials used for developing noninvasive, noncontact, precise, and controllable medical devices in a wide range of biomedical applications, including photothermal therapy, photodynamic therapy, drug delivery, and regenerative medicine. Herein, a range of biomaterials is discussed, including carbon-based nanomaterials, gold nanoparticles, graphite carbon nitride, transition metal dichalcogenides, and up-conversion nanoparticles that are used in the design of light-responsive medical devices. The importance of these light-responsive biomaterials is explored to design light-guided nanovehicle, modulate cellular behavior, as well as regulate extracellular microenvironments. Additionally, future perspectives on the clinical use of light-responsive biomaterials are highlighted.

Direct Conjugation of Retinoic Acid with Gold Nanoparticles to Improve Neural Differentiation of Human Adipose Stem Cells

Gold nanoparticles (AuNPs) have been proposed as useful medical carriers in the field of regenerative medicine. This study aimed to assess the direct conjugation ability of retinoic acid (RA) with AuNPs and to develop a strategy to differentiate the human adipose-derived stromal/stem cells (hADSCs) into neurons using AuNPs-RA. The physical properties of this nanocarrier were characterized using FT-IR, TEM, and FE-SEM. Moreover, the efficiency of RA conjugation on AuNPs was determined at 99% using UV-Vis spectroscopy. According to the MTT assay, an RA concentration of 66 μM caused a 50% inhibition of cell viability and AuNPs were not cytotoxic in concentrations below 5 μg/ml. Real-time PCR and immunocytochemistry proved that AuNPs-RA is able to increase the expression of neuronal marker genes and the number of neuronal protein (GFAP and MAP2)-positive cells, 14 days post-induction of hADSCs. Taken together, these results confirmed that the AuNPs-RA promote the neuronal differentiation of hADSCs.

A Multiscale Model to Predict Neuronal Cell Deformation with Varying Extracellular Matrix Stiffness and Topography

INTRODUCTION

Neuronal cells are sensitive to mechanical properties of extracellular matrix (ECM) such as stiffness and topography. Cells contract and exert a force on ECM to detect the microenvironment, which activates the signaling pathway to influence the cell functions such as differentiation, migration, and proliferation. There are numerous transmembrane proteins that transmit signals; however, integrin and neural cellular adhesion molecules (NCAM) play an important role in sensing the ECM mechanical properties. Mechanotransduction of cell-ECM is the key to understand the influence of ECM stiffness and topography; therefore, in this study, we develop a multiscale computational model to investigate these properties.

METHODS

This model couples the molecular behavior of integrin and NCAM to microscale interactions of neuronal cell and the ECM. We analyze the atomistic/molecular behavior of integrin and NCAM due to mechanical stimuli using steered molecular dynamics. The microscale properties of the neuronal cell and the ECM are simulated using non-linear finite element analysis by applying cell contractility.

RESULTS

We predict that by increasing the ECM stiffness, a neuronal cell exerts greater stress on the ECM. However, this stress reaches a saturation value for a threshold stiffness of ECM, and the saturation value is affected by the ECM thickness, topography, and clustering of integrin and NCAMs. Further, the ECM topography leads to asymmetric stress and deformation in the neuronal cell. Predicted stress distribution in neuronal cell and ECM are consistent with experimental results from the literature.

CONCLUSION

The multiscale computational model will guide in selecting the optimal ECM stiffness and topography range for in vitro studies.

Controlled Dynamics of Neural Tumor Cells by Templated Liquid Crystalline Polymer Networks

The ability to control the alignment and organization of cell populations has great potential for tissue engineering and regenerative medicine. A variety of approaches such as nano/microtopographical patterning, mechanical loading, and nanocomposite synthesis have been developed to engineer scaffolds able to control cellular properties and behaviors. In this work, a patterned liquid crystal polymer network (LCN) film is synthesized by using a nematic liquid crystal template in which the molecular orientations are predesigned by photopatterning technique. Various configurations of polymer networks such as linear and circular patterns are created. When neural tumor cells are plated onto the templated LCN films, the cell alignment, migration, and proliferation are directed in both linear and curvilinear fashions following the pattern of the aligned polymer chains. A complex LCN pattern with zigzag geometry is also fabricated and found to be capable of controlling cell alignment and collective cellular organization. The demonstrated control of cell dynamics and organization by LCN films with various molecular alignments opens new opportunities to design scaffolds to control cultured cell organization in a manner resembling that found in tissues and to develop novel advanced materials for nerve repair, tissue engineering, and regenerative medicine applications.

Dual Pathway for Promotion of Stem Cell Neural Differentiation Mediated by Gold Nanocomposites

The neural differentiation of embryonic stem cells (ESCs) is of great value in the treatment of neurodegenerative diseases. On the basis of the two related signaling pathways that direct the neural differentiation of ESCs, we used gold nanoparticles (GNP) as a means of combining chemical and physical cues to trigger the neurogenic differentiation of stem cells. Neural differentiation-related functional units (glyco and sulfonate units on glycosaminoglycans, GAG) were anchored on the GNP surface and were then transferred to the cell membrane surface via GNP-membrane interactions. The functional units were able to activate the GAG-related signaling pathway, in turn promoting differentiation and maturation of stem cells into neuronal lineages. In addition, using the photothermal effect of GNP, the differentiation-inducing factor retinoic acid (RA), could be actively delivered into cells via laser irradiation. The RA-related intracellular signaling pathway was thereby further triggered, resulting in strong promotion of neurogenesis with a 300-fold increase in mature neural marker expression. The gold nanocomposites developed in this work provide the basis for a new strategy directing ESCs differentiation into nerve cells with high efficiency and high purity by acting on two related signaling pathways.

Biomimetic Materials and Their Utility in Modeling the 3-Dimensional Neural Environment

The brain is a complex 3-dimensional structure, the organization of which provides a local environment that directly influences the survival, proliferation, differentiation, migration, and plasticity of neurons. To probe the effects of damage and disease on these cells, a synthetic environment is needed. Three-dimensional culturing of stem cells, neural progenitors, and neurons within fabricated biomaterials has demonstrated superior biomimetic properties over conventional 2-dimensional cultureware, offering direct recapitulation of both cell-cell and cell-extracellular matrix interactions. Within this review we address the benefits of deploying biomaterials as advanced cell culture tools capable of influencing neuronal fate and as in vitro models of the native in vivo microenvironment. We highlight recent and promising biomaterials approaches toward understanding neural network and their function relevant to neurodevelopment and provide our perspective on how these materials can be engineered and programmed to study both the healthy and diseased nervous system.

Nanostructured Modulators of Neuroglia

Biological and synthetic nanostructures can influence both glia and neurons in the central nervous system. Neurons represent only a small proportion (about 10%) of cells in the brain, whereas glial cells are the most abundant cell type. Non-targeted nanomedicines are mainly internalized by glia, in particular microglia, and to a lesser extent by astrocytes. Internalized nanomedicines by glia indirectly modify the functional status of neurons. The mechanisms of biochemical, morphological and functional changes of neural cells exposed to nanomedicines are still not well-understood. This minireview provides a cross-section of morphological and biochemical changes in glial cells and neurons exposed to different classes of hard and soft nanostructures.

High-Dose Neural Stem/Progenitor Cell Transplantation Increases Engraftment and Neuronal Distribution and Promotes Functional Recovery in Rats after Acutely Severe Spinal Cord Injury

Severe spinal cord injury (SCI) leads to permanent, complete paraplegia and places considerable mental and economic burdens on patients, compared with mild to moderate SCI. However, the dose-related effects of the neural stem/precursor cell (NSPC) transplantation on the injury microenvironment, NSPC survival, axonal growth, neuronal distribution, the composition of neurons, oligodendrocytes, and astrocytes in the lesion area and functional recovery have not yet been quantitatively evaluated in the context of severe SCI. In our study, we acutely transplanted 2.5 × 10⁴ or 1.5 × 10⁵ NSPCs/μl into the site of transection SCI. We found that high-dose NSPC transplantation exerted immunomodulatory and neuroprotective effects in the acute phase of severe SCI. In addition, one week later, a remarkable positive relationship was observed between the transplantation dose and the number of surviving NSPCs in severe SCI. At 8 weeks postgrafting, subjects that received the higher cell dose exhibited abundant nerve regeneration, extensive neuronal distribution, increased proportions of neurons and oligodendrocytes, and nascent functional neural network formation in the lesion area. Notably, a significant functional recovery was also observed. Our data suggest that it is important to consider potential dose-related effects on donor cell survival, neuronal distribution, and locomotor recovery in the development of preclinical NSPC transplantation therapy for severe SCI.

Wireless near-infrared electrical stimulation of neurite outgrowth

Herein, through using electropolymerized pyrrole (PPy) to coat near-infrared upconversion nanoparticles (UCNPs) on an indium tin oxide (ITO) electrode, the as-prepared PPy/UCNPs photoelectrode could generate an interfacial electric field, release rare earth ions and induce reactive oxygen species (ROS) in PC12 cells under NIR irradiation, which could realize wireless neurite development and outgrowth.

Molybdenum disulfide nanoflowers mediated anti-inflammation macrophage modulation for spinal cord injury treatment

Spinal cord injury (SCI) can cause locomotor dysfunctions and sensory deficits. Evidence shows that functional nanodrugs can regulate macrophage polarization and promote anti-inflammatory cytokine expression, which is feasible in SCI immunotherapeutic treatments. Molybdenum disulfide (MoS₂) nanomaterials have garnered great attention as potential carriers for therapeutic payload. Herein, we synthesize MoS₂@PEG (MoS₂ = molybdenum disulfide, PEG = poly (ethylene glycol)) nanoflowers as an effective carrier for loading etanercept (ET) to treat SCI. We characterize drug loading and release properties of MoS₂@PEG in vitro and demonstrate that ET-loading MoS₂@PEG obviously inhibits the expression of M1-related pro-inflammatory markers (TNF-α, CD86 and iNOS), while promoting M2-related anti-inflammatory markers (Agr1, CD206 and IL-10) levels. In vivo, the mouse model of SCI shows that long-circulating ET-MoS₂@PEG nanodrugs can effectively extravasate into the injured spinal cord up to 96 h after SCI, and promote macrophages towards M2 type polarization. As a result, the ET-loading MoS₂@PEG administration in mice can protect survival motor neurons, thus, reducing injured areas at central lesion sites, and significantly improving locomotor recovery. This study demonstrates the anti-inflammatory and neuroprotective activities of ET-MoS₂@PEG and promising utility of MoS₂ nanomaterial-mediated drug delivery.

Multifunctional Nanobiohybrid Material Composed of Ag@Bi2Se3/RNA Three-Way Junction/miRNA/Retinoic Acid for Neuroblastoma Differentiation

Nanoparticle-based cell differentiation therapy has attracted increasing research interest as it is a promising substitute for conventional cancer treatment methods. Here, the topological insulator bismuth selenide nanoparticle (Bi₂Se₃ NP) was core-shelled with silver (Ag@Bi₂Se₃) to represent remarkable biocompatibility and plasmonic features (ca. 2.3 times higher than those of Ag nanoparticle). Moreover, a newly developed RNA three-way junction (3WJ) structure was designed for the quad-functionalization of any type of nanoparticle and surface. One leg of the 3WJ was attached to the Ag@Bi₂Se₃, and the other leg harbored a cell-penetrating RNA and a florescence tag. The third leg was designed to inhibit micro-RNA-17 (miR-17) and to further release retinoic acid (RA). A new drug delivery mechanism was developed for the slow release of RA inside the cytosol based on the prerequisite inhibition of miR-17 using a strand displacement strategy. In this paper, we report a simple methodology for resolving the hydrophobicity challenges of RA by its conjugation with a RNA strand (RA/R) through a stimulus-responsive cross-linker. The developed nanobiohybrid material could fully differentiate SH-SY5Y cancer cells into neurons and stop their growth in 6 days without requiring sequential treatments which has not been reported yet. Using a surface-enhanced Raman spectroscopy technique, the RA delivery and the cell differentiation process were monitored nondestructively in real time. The fabricated nanobiohybrid material could open the new horizons in the fabrication of different diagnostic/therapeutic agents.

Photoconductive Micro/Nanoscale Interfaces of a Semiconducting Polymer for Wireless Stimulation of Neuron-Like Cells

We report multiscale structured fibers and patterned films based on a semiconducting polymer, poly(3-hexylthiophene) (P3HT), as photoconductive biointerfaces to promote neuronal stimulation upon light irradiation. The micro/nanoscale structures of P3HT used for neuronal interfacing and stimulation include nanofibers with an average diameter of 100 nm, microfibers with an average diameter of about 1 μm, and lithographically patterned stripes with width of 3, 25, and 50 μm, respectively. The photoconductive effect of P3HT upon light irradiation provides electrical stimulation for neuronal differentiation and directed growth. Our results demonstrate that neurons on P3HT nanofibers showed a significantly higher total number of branches, while neurons grown on P3HT microfibers had longer and thinner neurites. Such a combination strategy of topographical and photoconductive stimulation can be applied to further enhance neuronal differentiation and directed growth. These photoconductive polymeric micro/nanostructures demonstrated their great potential for neural engineering and development of novel neural regenerative devices.

Near-Infrared Manipulation of Membrane Ion Channels via Upconversion Optogenetics

Membrane ion channels are ultimately responsible for the propagation and integration of electrical signals in the nervous, muscular, and other systems. Their activation or malfunctioning plays a significant role in physiological and pathophysiological processes. Using optogenetics to dynamically and spatiotemporally control ion channels has recently attracted considerable attention. However, most of the established optogenetic tools (e.g., channelrhodopsins, ChRs) for optical manipulations, are mainly stimulated by UV or visible light, which raises the concerns of potential photodamage, limited tissue penetration, and high-invasive implantation of optical fiber devices. Near-infrared (NIR) upconversion nanoparticle (UCNP)-mediated optogenetic systems provide great opportunities for overcoming the problems encountered in the manipulation of ion channels in deep tissues. Hence, this review focuses on the recent advances in NIR regulation of membrane ion channels via upconversion optogenetics in biomedical research. The engineering and applications of upconversion optogenetic systems by the incorporation multiple emissive UCNPs into various light-gated ChRs/ligands are first elaborated, followed by a detailed discussion of the technical improvements for more precise and efficient control of membrane channels. Finally, the future perspectives for refining and advancing NIR-mediated upconversion optogenetics into in vivo even in clinical applications are proposed.

Electroactive Scaffolds for Neurogenesis and Myogenesis: Graphene-Based Nanomaterials

One of the major issues in tissue engineering is constructing a functional scaffold to support cell growth and also provide proper synergistic guidance cues. Graphene-based nanomaterials have emerged as biocompatible and electroactive scaffolds for neurogenesis and myogenesis, due to their excellent tunable chemical, physical, and mechanical properties. This review first assesses the recent investigations focusing on the fabrication and applications of graphene-based nanomaterials for neurogenesis and myogenesis, in the form of either 2D films, 3D scaffolds, or composite architectures. Besides, because of their outstanding electrical properties, graphene family materials are particularly suitable for designing electroactive scaffolds that could provide proper electrical stimulation (i.e., electrical or photo stimuli) to promote the regeneration of excitable neurons and muscle cells. Therefore, the effects and mechanism of electrical and/or photo stimulations on neurogenesis and myogenesis are followed. Furthermore, studies on their biocompatibilities and toxicities especially to neural and muscle cells are evaluated. Finally, the future challenges and perspectives in facilitating the development of clinical translation of graphene-family nanomaterials in treating neurodegenerative and muscle diseases are discussed.

Controlled Arrangement of Neuronal Cells on Surfaces Functionalized with Micropatterned Polymer Brushes

Conventional in vitro cultures are useful to represent simplistic neuronal behavior; however, the lack of organization results in random neurite spreading. To overcome this problem, control over the directionality of SH-SY5Y cells was attained, utilizing photolithography to pattern the cell-repulsive anionic brush poly(potassium 3-sulfopropyl methacrylate) (PKSPMA) into tracks of 20, 40, 80, and 100 μm width. These data validate the use of PKSPMA brush coatings for a long-term culture of the SH-SY5Y cells, as well as providing a methodology by which the precise deposition of PKSPMA can be utilized to achieve a targeted control over the SH-SY5Y cells. Specifically, the PKSPMA brush patterns prevented cell attachment, allowing the SH-SY5Y cells to grow only on noncoated glass (gaps of 20, 50, 75, and 100 μm width) at different cell densities (5000, 10 000, and 15 000 cells/cm2). This research demonstrates the importance of achieving cell directionality in vitro, while these simplistic models could provide new platforms to study complex neuron-neuron interactions.

Challenges and research progress of the use of mesenchymal stem cells in the treatment of ischemic stroke

Cerebral Ischemic Stroke (CIS) has become a hot issue in medical research because of the diversity of risk factors and the uncertainty of prognosis. In the field of regenerative medicine, mesenchymal stem cells (MSCs) have an increasingly prominent position due to their advantages of multiple differentiation, low immunogenicity and wide application. In the basic and clinical research of CIS, there are still some problems to be solved in the treatment of CIS. This paper will discuss the progresses and some obstacles of current MSCs for the treatment of CIS.

Systematic assessment of surface functionality on nanoscale patterns for topographic contact guidance of cells

The ability of surface topography to influence cellular response has been widely accepted, leading the way towards the development of potential neural prosthetics.

Biofunctionalized and self-supported polypyrrole frameworks as nanostructured ECM-like biointerfaces

Hybrid nanobiointerfaces were designed as an original contribution to the challenge of synthesizing nanostructured biomaterials integrating a set of cell fate-determining cues, originally provided to cells by the extracellular matrix (ECM). The produced biointerfaces consist of a stiff framework of intersected polypyrrole (PPy) nanotubes supporting a soft multilayer composed of ECM-derived biomacromolecules: collagen (Col) and hyaluronic acid (HA). PPy frameworks with highly tunable characteristics were synthesized through chemical oxidative polymerization of pyrrole monomers, templated within track-etched polycarbonate (PC) membranes featuring a network of intersected nanopores. PPy interfaces with a porosity of 80%, composed of nanotubes with an average diameter ranging from 40 to 300 nm, intersecting at an angle of 90°, were shown to be self-supported. These rigid PPy nanostructured interfaces were functionalized with a self-assembling (HA/Col) multilayer deposited via a layer-by-layer process. Biofunctionalized and unmodified PPy frameworks were both shown to promote sustained cell adhesion, therefore demonstrating the cytocompatibility of the engineered matrices. Such nanobiointerfaces, combining a mechanically-stable framework of tunable dimensions with a soft biopolymeric multilayer of highly versatile nature, pave the way towards cell-instructive biomaterials able to gather a wide range of cues guiding cell behavior. The developed self-supported structures could be used as a coating or as membranes bridging different tissues.

A versatile template-based approach allows for the synthesis of nanostructured biointerfaces, made of core–shell nanotubes, combining bioactivity and mechanical stability.

Graphene Based Materials in Neural Tissue Regeneration

Due to its extraordinary features such as large surface area, high electrical conductivity, chemical stability and mechanical properties, graphene attracts great interest in various fields of biomedical sciences including biosensors, cancer therapy, diagnosis and regenerative medicine. The use of graphene-based materials has been of great interest for the design of scaffolds that can promote neural tissue regeneration. Recent studies published over the last few years clearly show that graphene and graphene based materials promote adhesion, proliferation and differentiation of various cells including embryonic stem cells (ESC), neural stem cells (NSC), mesenchymal stem cells (MSC) and induced pluripotent stem cells (iPSC). Therefore graphene based materials are one of the promising nanoplatforms in regenerative medicine for neural tissue injury. With its unique topographic and chemical properties, graphene is used as a scaffold that could provide a bridge between regenerating nerves. More importantly, as a conductive substrate, graphene allows the continuation of electrical conduction between damaged nerve ends. The integration of supportive cells such as glial, neural precursor or stem cells in such a scaffold shows higher regeneration when compared to currently used neural autografts and nerve conduits. This review discusses the details of such studies involving graphene based materials with a special interest on neural stem cells, mesenchymal stem cells or pluripotent stem cells.

Nanotechnology for Neuroscience: Promising Approaches for Diagnostics, Therapeutics and Brain Activity Mapping

Unlocking the secrets of the brain is a task fraught with complexity and challenge - not least due to the intricacy of the circuits involved. With advancements in the scale and precision of scientific technologies, we are increasingly equipped to explore how these components interact to produce a vast range of outputs that constitute function and disease. Here, an insight is offered into key areas in which the marriage of neuroscience and nanotechnology has revolutionized the industry. The evolution of ever more sophisticated nanomaterials culminates in network-operant functionalized agents. In turn, these materials contribute to novel diagnostic and therapeutic strategies, including drug delivery, neuroprotection, neural regeneration, neuroimaging and neurosurgery. Further, the entrance of nanotechnology into future research arenas including optogenetics, molecular/ion sensing and monitoring, and piezoelectric effects is discussed. Finally, considerations in nanoneurotoxicity, the main barrier to clinical translation, are reviewed, and direction for future perspectives is provided.

Polymer Pen Lithography with Lipids for Large-Area Gradient Patterns

Gradient patterns comprising bioactive compounds over comparably (in regard to a cell size) large areas are key for many applications in the biomedical sector, in particular, for cell screening assays, guidance, and migration experiments. Polymer pen lithography (PPL) as an inherent highly parallel and large area technique has a great potential to serve in the fabrication of such patterns. We present strategies for the printing of functional phospholipid patterns via PPL that provide tunable feature size and feature density gradients over surface areas of several square millimeters. By controlling the printing parameters, two transfer modes can be achieved. Each of these modes leads to different feature morphologies. By increasing the force applied to the elastomeric pens, which increases the tip-surface contact area and boosts the ink delivery rate, a switch between a dip-pen nanolithography (DPN) and a microcontact printing (μCP) transfer mode can be induced. A careful inking procedure ensuring a homogeneous and not-too-high ink-load on the PPL stamp ensures a membrane-spreading dominated transfer mode, which, used in combination with smooth and hydrophilic substrates, generates features with constant height, independently of the applied force of the pens. Ultimately, this allows us to obtain a gradient of feature sizes over a mm² substrate, all having the same height on the order of that of a biological cellular membrane. These strategies allow the construction of membrane structures by direct transfer of the lipid mixture to the substrate, without requiring previous substrate functionalization, in contrast to other molecular inks, where structure is directly determined by the printing process itself. The patterns are demonstrated to be viable for subsequent protein binding, therefore adding to a flexible feature library when gradients of protein presentation are desired.

A Comparison of Lysosomal Enzymes Expression Levels in Peripheral Blood of Mild- and Severe-Alzheimer's Disease and MCI Patients: Implications for Regenerative Medicine Approaches

The association of lysosomal dysfunction and neurodegeneration has been documented in several neurodegenerative diseases, including Alzheimer's Disease (AD). Herein, we investigate the association of lysosomal enzymes with AD at different stages of progression of the disease (mild and severe) or with mild cognitive impairment (MCI). We conducted a screening of two classes of lysosomal enzymes: glycohydrolases (β-Hexosaminidase, β-Galctosidase, β-Galactosylcerebrosidase, β-Glucuronidase) and proteases (Cathepsins S, D, B, L) in peripheral blood samples (blood plasma and PBMCs) from mild AD, severe AD, MCI and healthy control subjects. We confirmed the lysosomal dysfunction in severe AD patients and added new findings enhancing the association of abnormal levels of specific lysosomal enzymes with the mild AD or severe AD, and highlighting the difference of AD from MCI. Herein, we showed for the first time the specific alteration of β-Galctosidase (Gal), β-Galactosylcerebrosidase (GALC) in MCI patients. It is notable that in above peripheral biological samples the lysosomes are more sensitive to AD cellular metabolic alteration when compared to levels of Aβ-peptide or Tau proteins, similar in both AD groups analyzed. Collectively, our findings support the role of lysosomal enzymes as potential peripheral molecules that vary with the progression of AD, and make them useful for monitoring regenerative medicine approaches for AD.

Directing Stem Cell Differentiation via Electrochemical Reversible Switching between Nanotubes and Nanotips of Polypyrrole Array

Control of stem cell behaviors at solid biointerfaces is critical for stem-cell-based regeneration and generally achieved by engineering chemical composition, topography, and stiffness. However, the influence of dynamic stimuli at the nanoscale from solid biointerfaces on stem cell fate remains unclear. Herein, we show that electrochemical switching of a polypyrrole (Ppy) array between nanotubes and nanotips can alter surface adhesion, which can strongly influence mechanotransduction activation and guide differentiation of mesenchymal stem cells (MSCs). The Ppy array, prepared via template-free electrochemical polymerization, can be reversibly switched between highly adhesive hydrophobic nanotubes and poorly adhesive hydrophilic nanotips through an electrochemical oxidation/reduction process, resulting in dynamic attachment and detachment to MSCs at the nanoscale. Multicyclic attachment/detachment of the Ppy array to MSCs can activate intracellular mechanotransduction and osteogenic differentiation independent of surface stiffness and chemical induction. This smart surface, permitting transduction of nanoscaled dynamic physical inputs into biological outputs, provides an alternative to classical cell culture substrates for regulating stem cell fate commitment. This study represents a general strategy to explore nanoscaled interactions between stem cells and stimuli-responsive surfaces.

Neuroregeneration versus neurodegeneration: toward a paradigm shift in Alzheimer's disease drug discovery

Alzheimer's disease represents an enormous global burden in terms of human suffering and economic cost. To tackle the current lack of effective drugs and the continuous clinical trial failures might require a shift from the prevailing paradigm targeting pathogenesis to the one targeting neural stem cells (NSCs) regeneration. In this context, small molecules have come to the forefront for their potential to manipulate NSCs, provide therapeutic tools and unveil NSCs biology. Classically, these molecules have been generated either by target-based or phenotypic approaches. To circumvent specific liabilities, nanomedicines emerge as a feasible alternative. However, this review is not intended to be comprehensive. Its purpose is to focus on recent examples that could accelerate development of neuroregenerative drugs against Alzheimer's disease.

Gold nanoparticles enhance the differentiation of embryonic stem cells into dopaminergic neurons via mTOR/p70S6K pathway

AIM

This study aimed to investigate the effect of gold nanoparticles (AuNPs) on differentiation of mouse embryonic stem cells (ESCs) into dopaminergic (DA) neurons and explore the possible underlying molecular mechanisms.

MATERIALS & METHODS

The efficiency of AuNPs on DA neuron differentiation was evaluated by observing fluorescence in TH promoter-engineered GFP-reporter ESCs, western blot and real-time PCR. The possible signal pathway was determined by western blot.

RESULTS

Compared with feeder-free control condition, AuNPs are able to enhance fate specification of ESCs into DA neurons. Moreover, mTOR/p70S6K signaling pathway was found involving in this AuNPs-mediated DA neuron differentiation.

CONCLUSION

Our findings may lead future insight investigation into the underlying mechanisms and potential application of AuNPs in stem cell research.

A suspended carbon fiber culture to model myelination by human Schwann cells

Understanding of myelination/remyelination process is essential to guide tissue engineering for nerve regeneration. In vitro models currently used are limited to cell population studies and cannot easily identify individual cell contribution to the process. We established a novel model to study the contribution of human Schwann cells to the myelination process. The model avoids the presence of neurons in culture; Schwann cells respond solely to the biophysical properties of an artificial axon. The model uses a single carbon fiber suspended in culture media far from the floor of the well. The fiber provides an elongated structure of defined diameter with 360-degree of surface available for human Schwann cells to wrap around. This model enabled us to spatially and temporally track the myelination by individual Schwann cells along the fiber. We observed cell attachment, elongation and wrapping over a period of 9 days. Cells remained alive and expressed Myelin Basic Protein and Myelin Associated Glycoprotein as expected. Natural and artificial molecules, and external physical factors (e.g., p atterned electrical impulses), may be tested with this model as possible regulators of myelination.

Polymer Conformation under Confinement

The conformation of polymer chains under confinement is investigated in intercalated polymer/layered silicate nanocomposites. Hydrophilic poly(ethylene oxide)/sodium montmorillonite, PEO/Na⁺-MMT, hybrids were prepared utilizing melt intercalation with compositions where the polymer chains are mostly within the ~1 nm galleries of the inorganic material. The polymer chains are completely amorphous in all compositions even at temperatures where the bulk polymer is highly crystalline. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) is utilized to investigate the conformation of the polymer chains over a broad range of temperatures from below to much higher than the bulk polymer melting temperature. A systematic increase of the gauche conformation relatively to the trans is found with decreasing polymer content both for the C⁻C and the C⁻O bonds that exist along the PEO backbone indicating that the severe confinement and the proximity to the inorganic surfaces results in a more disordered state of the polymer.