A self-assembling nanomaterial reduces acute brain injury and enhances functional recovery in a rat model of intracerebral hemorrhage

Nanomaterial technologies for precision diagnosis and treatment of brain hemorrhage

Brain hemorrhage events present complex clinical challenges due to their rapid progression and the intricate interplay of oxidative stress, inflammation, and neuronal damage. Traditional diagnostic and therapeutic approaches often struggle to meet the demands for timely and effective intervention. This review explores the cutting-edge role of nanomaterials in transforming cerebral hemorrhage management, focusing on both diagnostic and therapeutic advancements. Nanomaterial-enabled imaging techniques, such as optical imaging, magnetic resonance imaging, and magnetic particle imaging, significantly enhance the accuracy of hemorrhage detection by providing real-time, high-resolution assessments of blood-brain barrier (BBB) integrity, cerebral perfusion, and hemorrhage progression, which is critical for guiding intervention strategies. On the therapeutic front, nanomaterial-based systems enable the precise delivery of drugs and bioactive molecules, fostering neural repair and functional recovery while minimizing systemic side effects. Furthermore, multifunctional nanomaterials not only address the primary injury but also offer precise control over secondary injuries, such as edema and oxidative stress. Their ability to enhance neuroprotection, prevent re-bleeding, and stimulate brain tissue regeneration provides a holistic approach and marks a significant advancement in brain hemorrhage therapy. As the field continues to advance, nanotechnology is set to fundamentally reshape the clinical management and long-term outcomes of brain hemorrhages, presenting a paradigm shift towards personalized and highly effective neurological care.

Nanobiotechnologies for stroke treatment

Stroke has brought about a poor quality of life for patients and a substantial societal burden with high morbidity and mortality. Thus, the efficient stroke treatment has always been the hot topic in the research of medicine. In the past decades, nanobiotechnologies, including natural exosomes and artificial nanomaterials, have been a focus of attention for stroke treatment due to their inherent advantages, such as facile blood - brain barrier traversal and high drug encapsulation efficiency. Recently, thanks to the rapid development of nanobiotechnologies, more and more efforts have been made to study the therapeutic effects of exosomes and artificial nanomaterials as well as relevant mechanisms in stroke treatment. Herein, from recent studies and articles, the application of natural exosomes and artificial nanomaterials in stroke treatment are summarized. And their prospects of clinical translation and future development are also discussed in further detail.

Drug delivery strategy of hemostatic drugs for intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is associated with high rates of mortality and disability, underscoring an urgent need for effective therapeutic interventions. The clinical prognosis of ICH remains limited, primarily due to the absence of targeted, precise therapeutic options. Advances in novel drug delivery platforms, including nanotechnology, gel-based systems, and exosome-mediated therapies, have shown potential in enhancing ICH management. This review delves into the pathophysiological mechanisms of ICH and provides a thorough analysis of existing treatment strategies, with an emphasis on innovative drug delivery approaches designed to address critical pathological pathways. We assess the benefits and limitations of these therapies, offering insights into future directions in ICH research and highlighting the transformative potential of next-generation drug delivery systems in improving patient outcomes.

Intracerebral Administration of a Novel Self-Assembling Peptide Hydrogel Is Safe and Supports Cell Proliferation in Experimental Intracerebral Haemorrhage

Intracerebral haemorrhage (ICH) is the deadliest form of stroke, but current treatment options are limited, meaning ICH survivors are often left with life-changing disabilities. The significant unmet clinical need and socioeconomic burden of ICH mean novel regenerative medicine approaches are gaining interest. To facilitate the regeneration of the ICH lesion, injectable biomimetic hydrogels are proposed as both scaffolds for endogenous repair and delivery platforms for pro-regenerative therapies. In this paper, the objective was to explore whether injection of a novel self-assembling peptide hydrogel (SAPH) Alpha2 was feasible, safe and could stimulate brain tissue regeneration, in a collagenase-induced ICH model in rats. Alpha2 was administered intracerebrally at 7 days post ICH and functional outcome measures, histological markers of damage and repair and RNA-sequencing were investigated for up to 8 weeks. The hydrogel Alpha2 was safe, well-tolerated and was retained in the lesion for several weeks, where it allowed infiltration of host cells. The hydrogel had a largely neutral effect on functional outcomes and expression of angiogenic and neurogenic markers but led to increased numbers of proliferating cells. RNAseq and pathway analysis showed that ICH altered genes related to inflammatory and phagocytic pathways, and these changes were also observed after administration of hydrogel. Overall, the results show that the novel hydrogel was safe when injected intracerebrally and had no negative effects on functional outcomes but increased cell proliferation. To elicit a regenerative effect, future studies could use a functionalised hydrogel or combine it with an adjunct therapy.

Application of biomaterials in the treatment of intracerebral hemorrhage

Although the current surgical hematoma removal treatment saves patients' lives in critical moments of intracerebral hemorrhage (ICH), the lethality and disability rates of ICH are still very high. Due to the individual differences of patients, postoperative functional improvement is still to be confirmed, and the existing drug treatment has limited benefits for ICH. Recent advances in biomaterials may provide new ideas for the therapy of ICH. This review first briefly describes the pathogenic mechanisms of ICH, including primary and secondary injuries such as inflammation and intracerebral edema, and briefly describes the existing therapeutic approaches and their limitations. Secondly, existing nanomaterials and hydrogels for ICH, including exosomes, liposomes, and polymer nanomaterials, are also described. In addition, the potential challenges and application prospects of these biomaterials for clinical translation in ICH treatment are discussed.

Perspective insights into versatile hydrogels for stroke: From molecular mechanisms to functional applications

As the leading killer of life and health, stroke leads to limb paralysis, speech disorder, dysphagia, cognitive impairment, mental depression and other symptoms, which entail a significant financial burden to society and families. At present, physiology, clinical medicine, engineering, and materials science, advanced biomaterials standing on the foothold of these interdisciplinary disciplines provide new opportunities and possibilities for the cure of stroke. Among them, hydrogels have been endowed with more possibilities. It is well-known that hydrogels can be employed as potential biosensors, medication delivery vectors, and cell transporters or matrices in tissue engineering in tissue engineering, and outperform many traditional therapeutic drugs, surgery, and materials. Therefore, hydrogels become a popular scaffolding treatment option for stroke. Diverse synthetic hydrogels were designed according to different pathophysiological mechanisms from the recently reported literature will be thoroughly explored. The biological uses of several types of hydrogels will be highlighted, including pro-angiogenesis, pro-neurogenesis, anti-oxidation, anti-inflammation and anti-apoptosis. Finally, considerations and challenges of using hydrogels in the treatment of stroke are summarized.

Advances of nanotechnology for intracerebral hemorrhage therapy

Intracerebral hemorrhage (ICH), the most devastating subtype of stoke, is of high mortality at 5 years and even those survivors usually would suffer permanent disabilities. Fortunately, various preclinical active drugs have been approached in ICH, meanwhile, the therapeutic effects of these pharmaceutical ingredients could be fully boosted with the assistance of nanotechnology. In this review, besides the pathology of ICH, some ICH therapeutically available active drugs and their employed nanotechnologies, material functions, and therapeutic principles were comprehensively discussed hoping to provide novel and efficient strategies for ICH therapy in the future.

Short Peptide Nanofiber Biomaterials Ameliorate Local Hemostatic Capacity of Surgical Materials and Intraoperative Hemostatic Applications in Clinics

Short designer self-assembling peptide (dSAP) biomaterials are a new addition to the hemostat group. It may provide a diverse and robust toolbox for surgeons to integrate wound microenvironment with much safer and stronger hemostatic capacity than conventional materials and hemostatic agents. Especially in noncompressible torso hemorrhage (NCTH), diffuse mucosal surface bleeding, and internal medical bleeding (IMB), with respect to the optimal hemostatic formulation, dSAP biomaterials are the ingenious nanofiber alternatives to make bioactive neural scaffold, nasal packing, large mucosal surface coverage in gastrointestinal surgery (esophagus, gastric lesion, duodenum, and lower digestive tract), epicardiac cell-delivery carrier, transparent matrix barrier, and so on. Herein, in multiple surgical specialties, dSAP-biomaterial-based nano-hemostats achieve safe, effective, and immediate hemostasis, facile wound healing, and potentially reduce the risks in delayed bleeding, rebleeding, post-operative bleeding, or related complications. The biosafety in vivo, bleeding indications, tissue-sealing quality, surgical feasibility, and local usability are addressed comprehensively and sequentially and pursued to develop useful surgical techniques with better hemostatic performance. Here, the state of the art and all-round advancements of nano-hemostatic approaches in surgery are provided. Relevant critical insights will inspire exciting investigations on peptide nanotechnology, next-generation biomaterials, and better promising prospects in clinics.

A hyaluronic acid/silk fibroin/poly-dopamine-coated biomimetic hydrogel scaffold with incorporated neurotrophin-3 for spinal cord injury repair

Bio-factor stimulation is essential for axonal regeneration in the central nervous system. Thus, persistent and efficient factor delivery in the local microenvironment is an ideal strategy for spinal cord injury repair. We developed a biomimetic hydrogel scaffold to load biofactors in situ and release them in a controlled way as a promising therapeutic modality. Hyaluronic acid and silk fibroin were cross-linked as the basement of the scaffolds, and poly-dopamine coating was used to further increase the loading of factors and endow the hydrogel scaffolds with ideal physical and chemical properties and proper biocompatibility. Notably, neurotrophin-3 release from the hydrogel scaffolds was prolonged to 28 days. A spinal cord injury model was constructed for hydrogel scaffold transplantation. After eight weeks, significant NF200-positive nerve fibers were observed extending across the glial scar to the center of the injured area. Due to the release of neurotrophin-3, spinal cord regeneration was enhanced, and the cavity area of the injury graft site and inflammation associated with CD68 positive cells were reduced, which led to a significant improvement in hind limb motor function. The results show that the hyaluronic acid/silk fibroin/poly-dopamine-coated biomimetic hydrogel scaffold achieved locally slow release of neurotrophin-3, thus facilitating the regeneration of injured spinal cord. STATEMENT OF SIGNIFICANCE: Hydrogels have received great attention in spinal cord regeneration. Current research has focused on more efficient and controlled release of bio-factors. Here, we adopted a mussel-inspired strategy to functionalize the hyaluronic acid/silk fibroin hydrogel scaffold to increase the load of neurotrophin-3 and extend the release time. The hydrogel scaffolds have ideal physiochemical properties, proper release rate, and biocompatibility. Owing to the continuous neurotrophin-3 release from implanted scaffolds, cavity formation is reduced, inflammation alleviated, and spinal cord regeneration enhanced, indicating great potential for bio-factor delivery in soft tissue regeneration applications.

Designed peptide amphiphiles as scaffolds for tissue engineering

Peptide amphiphiles (PAs) are peptide-based molecules that contain a peptide sequence as a head group covalently conjugated to a hydrophobic segment, such as lipid tails. They can self-assemble into well-ordered supramolecular nanostructures such as micelles, vesicles, twisted ribbons and nanofibers. In addition, the diversity of natural amino acids gives the possibility to produce PAs with different sequences. These properties along with their biocompatibility, biodegradability and a high resemblance to native extracellular matrix (ECM) have resulted in PAs being considered as ideal scaffold materials for tissue engineering (TE) applications. This review introduces the 20 natural canonical amino acids as building blocks followed by highlighting the three categories of PAs: amphiphilic peptides, lipidated peptide amphiphiles and supramolecular peptide amphiphile conjugates, as well as their design rules that dictate the peptide self-assembly process. Furthermore, 3D bio-fabrication strategies of PAs hydrogels are discussed and the recent advances of PA-based scaffolds in TE with the emphasis on bone, cartilage and neural tissue regeneration both in vitro and in vivo are considered. Finally, future prospects and challenges are discussed.

Application of nanomaterials in the treatment of intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a non-traumatic hemorrhage caused by the rupture of blood vessels in the brain parenchyma, with an acute mortality rate of 30%‒40%. Currently, available treatment options that include surgery are not promising, and new approaches are urgently needed. Nanotechnology offers new prospects in ICH because of its unique benefits. In this review, we summarize the applications of various nanomaterials in ICH. Nanomaterials not only enhance the therapeutic effects of drugs as delivery carriers but also contribute to several facets after ICH such as repressing detrimental neuroinflammation, resisting oxidative stress, reducing cell death, and improving functional deficits.

Vitamin D Enhances Hematoma Clearance and Neurologic Recovery in Intracerebral Hemorrhage

BACKGROUND

Erythrophagocytosis by reparative monocyte-derived macrophage contributes to hematoma clearance and neurological recovery after intracerebral hemorrhage (ICH). Vitamin D (VitD) is a neuroprotective hormone and regulates the differentiation of monocyte-derived macrophage from monocytes. In this study, we examined the effects of VitD supplementation on monocyte-derived macrophage and hematoma clearance in rodent with ICH.

METHODS

Neurobehavioral functions and hematoma volume were assessed using a collagenase injection model in both young- and middle-aged mice with or without VitD treatment given 2 hours post-ICH induction. We used flow cytometry to analyze CD36 expression and macrophage and undifferentiated monocyte cell numbers during in vivo erythrophagocytosis in collagenase and autologous blood injection models. Western blot analysis and immunofluorescence were used to assess the expression levels of the PPAR-γ (peroxisome proliferator-activated receptor γ)-CD36 axis and CD206. A macrophage differentiation study was conducted on murine bone marrow-derived monocytes.

RESULTS

VitD promoted neurological recovery and facilitated hematoma clearance in both young- and middle-aged mice after ICH. Within the perihematomal region, mature macrophages, rather than undifferentiated monocytes, expressed higher levels of CD36 in driving erythrocyte clearance. VitD increased the macrophage number but decreased the monocyte number and elevated the levels of CD36 and PPAR-γ in the brain. In vitro, VitD accelerated the differentiation of reparative macrophages from bone marrow-derived monocytes.

CONCLUSIONS

VitD promotes reparative macrophage differentiation, facilitates hematoma clearance, and improves neurobehavioral performance in mice with ICH, suggesting that VitD should be further examined as a potentially promising treatment for ICH.

Efficacy and histopathological effects of self-assembling peptides RADA16 and IEIK13 in neurosurgical hemostasis

There is a continued need for effective hemostatic agents that are safe for neurosurgical use. Self-assembling peptide hydrogels have been suggested as novel hemostatic agents. They offer some advantages for neurosurgical hemostasis (e.g., transparency), but their efficacy and safety for neurosurgery has not been established. In this paper, the efficacy and safety of two self-assembling peptides, RADA16 and IEIK13, are explored for hemostasis of oozing bleeding on the rat cerebral cortex (n=56). Chronic safety was evaluated by neuropathological evaluation at one, four, and twelve weeks after craniotomy (n=32). An inactive control and oxidized cellulose served as comparators. Mean time-to-hemostasis was significantly shorter for RADA16 and IEIK13 compared to controls, while safety evaluation yielded similar results. Histopathological response consisted primarily of macrophage infiltration at the lesion site in all groups. This study confirms the hemostatic potential and safety of RADA16 and IEIK13 for hemostasis in the rat brain.

Central Nervous System Tissue Regeneration after Intracerebral Hemorrhage: The Next Frontier

Despite marked advances in surgical techniques and understanding of secondary brain injury mechanisms, the prognosis of intracerebral hemorrhage (ICH) remains devastating. Harnessing and promoting the regenerative potential of the central nervous system may improve the outcomes of patients with hemorrhagic stroke, but approaches are still in their infancy. In this review, we discuss the regenerative phenomena occurring in animal models and human ICH, provide results related to cellular and molecular mechanisms of the repair process including by microglia, and review potential methods to promote tissue regeneration in ICH. We aim to stimulate research involving tissue restoration after ICH.

Regenerative Potential of Hydrogels for Intracerebral Hemorrhage: Lessons from Ischemic Stroke and Traumatic Brain Injury Research

Intracerebral hemorrhage (ICH) is a deadly and debilitating type of stroke, caused by the rupture of cerebral blood vessels. To date, there are no restorative interventions approved for use in ICH patients, highlighting a critical unmet need. ICH shares some pathological features with other acute brain injuries such as ischemic stroke (IS) and traumatic brain injury (TBI), including the loss of brain tissue, disruption of the blood-brain barrier, and activation of a potent inflammatory response. New biomaterials such as hydrogels have been recently investigated for their therapeutic benefit in both experimental IS and TBI, owing to their provision of architectural support for damaged brain tissue and ability to deliver cellular and molecular therapies. Conversely, research on the use of hydrogels for ICH therapy is still in its infancy, with very few published reports investigating their therapeutic potential. Here, the published use of hydrogels in experimental ICH is commented upon and how approaches reported in the IS and TBI fields may be applied to ICH research to inform the design of future therapies is described. Unique aspects of ICH that are distinct from IS and TBI that should be considered when translating biomaterial-based therapies between disease models are also highlighted.

Self-assembling peptides as vectors for local drug delivery and tissue engineering applications

Molecular self-assembly has forged a new era in the development of advanced biomaterials for local drug delivery and tissue engineering applications. Given their innate biocompatibility and biodegradability, self-assembling peptides (SAPs) have come in the spotlight of such applications. Short and water-soluble SAP biomaterials associated with enhanced pharmacokinetic (PK) and pharmacodynamic (PD) responses after the topical administration of the therapeutic systems, or improved regenerative potential in tissue engineering applications will be the focus of the current review. SAPs are capable of generating supramolecular structures using a boundless array of building blocks, while peptide engineering is an approach commonly pursued to encompass the desired traits to the end composite biomaterials. These two elements combined, expand the spectrum of SAPs multi-functionality, constituting them potent biomaterials for use in various biomedical applications.

Biosensing surfaces and therapeutic biomaterials for the central nervous system in COVID-19

COVID-19 can affect the central nervous system (CNS) indirectly by inflammatory mechanisms and even directly enter the CNS. Thereby, COVID-19 can evoke a range of neurosensory conditions belonging to infectious, inflammatory, demyelinating, and degenerative classes. A broad range of non-specific options, including anti-viral agents and anti-inflammatory protocols, is available with varying therapeutic. Due to the high mortality and morbidity in COVID-19-related brain damage, some changes to these general protocols, however, are necessary for ensuring the delivery of therapeutic(s) to the specific components of the CNS to meet their specific requirements. The biomaterials approach permits crossing the blood-brain barrier (BBB) and drug delivery in a more accurate and sustained manner. Beyond the BBB, drugs can protect neural cells, stimulate endogenous stem cells, and induce plasticity more effectively. Biomaterials for cell delivery exist, providing an efficient tool to improve cell retention, survival, differentiation, and integration. This paper will review the potentials of the biomaterials approach for the damaged CNS in COVID-19. It mainly includes biomaterials for promoting synaptic plasticity and modulation of inflammation in the post-stroke brain, extracellular vesicles, exosomes, and conductive biomaterials to facilitate neural regeneration, and artificial nerve conduits for treatment of neuropathies. Also, biosensing surfaces applicable to the first sensory interface between the host and the virus that encourage the generation of accelerated anti-viral immunity theoretically offer hope in solving COVID-19.

The use of bioactive matrices in regenerative therapies for traumatic brain injury

Functional deficits due to neuronal loss are a common theme across multiple neuropathologies, including traumatic brain injury (TBI). Apart from mitigating cell death, another approach to treating brain injuries involves re-establishing the neural circuitry at the lesion site by utilizing exogeneous and/or endogenous stem cells to achieve functional recovery. While there has been limited success, the emergence of new bioactive matrices that promote neural repair introduces new perspectives on the development of regenerative therapies for TBI. This review briefly discusses current development on cell-based therapies and the use of bioactive matrices, hydrogels in particular, when incorporated in regenerative therapies. Desirable characteristics of bioactive matrices that have been shown to augment neural repair in TBI models were identified and further discussed. Understanding the relative outcomes of newly developed biomaterials implanted in vivo can better guide the development of biomaterials as a therapeutic strategy, for biomaterial-based cellular therapies are still in their nascent stages. Nonetheless, the value of bioactive matrices as a treatment for acute brain injuries should be appreciated and further developed. STATEMENT OF SIGNIFICANCE: Cell-based therapies have received attention as an alternative therapeutic strategy to improve clinical outcome post-traumatic brain injury but have achieved limited success. Whilst the incorporation of newly developed biomaterials in regenerative therapies has shown promise in augmenting neural repair, studies have revealed new hurdles which must be overcome to improve their therapeutic efficacy. This review discusses the recent development of cell-based therapies with a specific focus on the use of bioactive matrices in the form of hydrogels, to complement cell transplantation within the injured brain. Moreover, this review consolidates in vivo animal studies that demonstrate relative functional outcome upon the implantation of different biomaterials to highlight their desirable traits to guide their development for regenerative therapies in traumatic brain injury.

Self-assembling RATEA16 peptide nanofiber designed for rapid hemostasis

In this study, we synthesized a novel polypeptide material, RATEA16, by the solid phase method, and investigated the secondary structure, self-assembly performance, gelation ability, biocompatibility and hemostatic efficiencyin vitroandin vivo.

White matter repair and treatment strategy after intracerebral hemorrhage

The predilection site of intracerebral hemorrhage (ICH) is in the basal ganglia, which is rich in white matter (WM) fiber bundles, such as cerebrospinal tract in the internal capsule. ICH induced damage to this area can easily lead to severe neurological dysfunction and affects the prognosis and quality of life of patients. At present, the pathophysiological mechanisms of white matter injury (WMI) after ICH have attracted researchers' attention, but studies on the repair and recovery mechanisms and therapy strategies remain rare. In this review, we mainly summarized the WM recovery and treatment strategies after ICH by updating the WMI-related content by reviewing the latest researches and proposing the bottleneck of the current research.

The Potential of Biomaterial-Based Approaches as Therapies for Ischemic Stroke: A Systematic Review and Meta-Analysis of Pre-clinical Studies

Background: In recent years pre-clinical stroke research has shown increased interest in the development of biomaterial-based therapies to promote tissue repair and functional recovery. Such strategies utilize biomaterials as structural support for tissue regeneration or as delivery vehicles for therapeutic agents. While a range of biomaterials have been tested in stroke models, currently no overview is available for evaluating the benefit of these approaches. We therefore performed a systematic review and meta-analysis of studies investigating the use of biomaterials for the treatment of stroke in experimental animal models. Methods: Studies were identified by searching electronic databases (PubMed, Web of Science) and reference lists of relevant review articles. Studies reporting lesion volume and/or neurological score were included. Standardized mean difference (SMD) and 95% confidence intervals were calculated using DerSimonian and Laird random effects. Study quality and risk of bias was assessed using the CAMARADES checklist. Publication bias was visualized by funnel plots followed by trim and fill analysis of missing publications. Results: A total of 66 publications were included in the systematic review, of which 44 (86 comparisons) were assessed in the meta-analysis. Overall, biomaterial-based interventions improved both lesion volume (SMD: -2.98, 95% CI: -3.48, -2.48) and neurological score (SMD: -2.3, 95% CI: -2.85, -1.76). The median score on the CAMARADES checklist was 5.5/10 (IQR 4.25-6). Funnel plots of lesion volume and neurological score data revealed pronounced asymmetry and publication bias. Additionally, trim and fill analysis estimated 19 "missing" studies for the lesion volume outcome adjusting the effect size to -1.91 (95% CI: -2.44, -1.38). Conclusions: Biomaterials including scaffolds and particles exerted a positive effect on histological and neurological outcomes in pre-clinical stroke models. However, heterogeneity in the field, publication bias and study quality scores which may be another source of bias call for standardization of outcome measures and improved study reporting.

A window into the brain: Tools to assess pre-clinical efficacy of biomaterials-based therapies on central nervous system disorders

Therapeutic conveyance into the brain is a cardinal requirement for treatment of diverse central nervous system (CNS) disorders and associated pathophysiology. Effectual shielding of the brain by the blood-brain barrier (BBB) sieves out major proportion of therapeutics with the exception of small lipophilic molecules. Various nano-delivery systems (NDS) provide an effective solution around this obstacle owing to their small size and targeting properties. To date, these systems have been used for several pre-clinical disease models including glioma, neurodegenerative diseases and psychotic disorders. An efficacy screen for these systems involves a test battery designed to probe into the multiple facets of therapeutic delivery. Despite their wide application in redressing various disease targets, the efficacy evaluation strategies for all can be broadly grouped into four modalities, namely: histological, bio-imaging, molecular and behavioural. This review presents a comprehensive insight into all of these modalities along with their strengths and weaknesses as well as perspectives on an ideal design for a panel of tests to screen brain nano-delivery systems.

Advances in Nano Neuroscience: From Nanomaterials to Nanotools

During the last decades, neuroscientists have increasingly exploited a variety of artificial, de-novo synthesized materials with controlled nano-sized features. For instance, a renewed interest in the development of prostheses or neural interfaces was driven by the availability of novel nanomaterials that enabled the fabrication of implantable bioelectronics interfaces with reduced side effects and increased integration with the target biological tissue. The peculiar physical-chemical properties of nanomaterials have also contributed to the engineering of novel imaging devices toward sophisticated experimental settings, to smart fabricated scaffolds and microelectrodes, or other tools ultimately aimed at a better understanding of neural tissue functions. In this review, we focus on nanomaterials and specifically on carbon-based nanomaterials, such as carbon nanotubes (CNTs) and graphene. While these materials raise potential safety concerns, they represent a tremendous technological opportunity for the restoration of neuronal functions. We then describe nanotools such as nanowires and nano-modified MEA for high-performance electrophysiological recording and stimulation of neuronal electrical activity. We finally focus on the fabrication of three-dimensional synthetic nanostructures, used as substrates to interface biological cells and tissues in vitro and in vivo.

Branched peptides integrate into self-assembled nanostructures and enhance biomechanics of peptidic hydrogels

Self-assembling peptides (SAP) have drawn an increasing interest in the tissue engineering community. They display unquestionable biomimetic properties, tailorability and promising biocompatibility. However their use has been hampered by poor mechanical properties making them fragile soft scaffolds. To increase SAP hydrogel stiffness we introduced a novel strategy based on multiple ramifications of (LDLK)₃, a well-known linear SAP, connected with one or multiple "lysine knots". Differently branched SAPs were tested by increasing the number of (LDLK)₃-like branches and by adding the neuro-regenerative functional motif BMHP1 as a single branch. While pure branched peptides did not have appealing self-assembling propensity, when mixed with the corresponding linear SAP they increased the stiffness of the overall hydrogel of multiple times. Notably, optimal results (or peak) were obtained 1) at similar molar ratio (between linear and branched peptides) for all tested sequences and 2) for the branched SAPs featuring the highest number of branches made of (LDLK)₃. The functional motif BMHP1, as expected, seemed not to contribute to the increase of the storage modulus as efficiently as (LDLK)₃. Interestingly, branched SAPs improved the β-sheet self-arrangement of (LDLK)₃ and allowed for the formation of assembled nanofibers. Indeed in coarse-grained molecular dynamics we showed they readily integrate in the assembled aggregates providing "molecular connections" among otherwise weakly paired β-structures. Lastly, branched SAPs did not affect the usual response of human neural stem cells cultured on (LDLK)₃-like scaffolds in vitro. Hence, branched SAPs may be a valuable new tool to enhance mechanical properties of self-assembling peptide biomaterials harmlessly; as neither chemical nor enzymatic cross-linking reactions are involved. As a consequence, branched SAPs may enlarge the field of application of SAPs in tissue engineering and beyond.

STATEMENT OF SIGNIFICANCE

Self-assembling peptides stand at the forefront of regenerative medicine because they feature biomimetic nano-architectures that mimic the complexity of natural peptide-based extracellular matrices of living tissues. Their superior biocompatibility and ease of scale-up production are hampered by weak mechanical properties due to transient non-covalent interactions among and within the self-assembled peptide chains, thus limiting their potential applications. We introduced new branched self-assembling peptides to be used as "molecular connectors" among self-assembled nanostructures made of linear SAPs. Branched SAPs could be mixed with linear SAPs before self-assembling in order to have them intermingled with different β-sheets of linear SAPs after gelation. This strategy caused a manifold increase of the stiffness of the assembled hydrogels (proportional to the number of self-assembling branches), did not affect SAP propensity to form β-sheet but, instead, further stimulated their secondary structure rearrangements. It is now possible to modularly improve SAP scaffold mechanical properties without using harmful chemical reactions. Therefore, branched SAPs represent an additional tool to be adopted for efficient and harmless SAP scaffold customization in tissue engineering.

Laminin-derived Ile-Lys-Val-ala-Val: a promising bioactive peptide in neural tissue engineering in traumatic brain injury

The adult brain has a very limited regeneration capacity and there is no effective treatment currently available for brain injury. Neuroprotective drugs aim to reduce the intensity of cell degeneration but do not trigger tissue regeneration. Cell replacement therapy is a novel strategy to overcome brain injury-induced disability. To enhance cell viability and neuronal differentiation, developing bioactive scaffolds combined with stem cells for transplantation is a crucial approach in brain tissue engineering. Cell interactions with the extracellular matrix (ECM) play a vital role in neuronal cell survival, neurite outgrowth, attachment, migration, differentiation, and proliferation. Thus, appropriate cell-ECM interactions are essential when designing and modifying scaffolds for application in neural tissue engineering. To improve cell-ECM interactions, scaffolds can be modified with bioactive peptides. Here, we discuss the characteristic features of laminin-derived Ile-Lys-Val-Ala-Val (IKVAV) sequence as a bio-functional motif in scaffolds and the behavior of stem cells in scaffolds conjugated with the IKVAV peptide. The incorporation of this bioactive peptide in nanofiber scaffolds markedly improves stem cell behavior and may be a potential method for cell replacement therapy in traumatic brain injury.

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.

Preclinical Studies and Translational Applications of Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) which refers to bleeding in the brain is a very deleterious condition with high mortality and disability rate. Surgery or conservative therapy remains the treatment option. Various studies have divided the disease process of ICH into primary and secondary injury, for which knowledge into these processes has yielded many preclinical and clinical treatment options. The aim of this review is to highlight some of the new experimental drugs as well as other treatment options like stem cell therapy, rehabilitation, and nanomedicine and mention some translational clinical applications that have been done with these treatment options.

Nano-hemostats and a Pilot Study of Their Use in a Large Animal Model of Major Vessel Hemorrhage in Endoscopic Skull Base Surgery

Nano-hemostats are synthetic amino acid chains that self-assemble into a scaffold under certain conditions. These have been shown to be effective in stopping bleeding in small animal models of hemorrhage. Proposed mechanisms for their effect are that they form a mesh analogous to the fibrin plug in native hemostasis and that they may potentiate both platelet activation and the coagulation cascade. These may potentially become valuable adjuncts to endoscopic skull base surgery where there is the potential for both major vessel injury and smaller perforator injury to eloquent areas where bipolar cautery may not be suitable. We present a summary of the clinical studies to date and a small pilot study of nano-hemostat in an endoscopic sheep model of major vessel hemorrhage to determine its efficacy in stopping bleeding in this potentially catastrophic complication.

Display of functional proteins on supramolecular peptide nanofibrils using a split-protein strategy

The display of functional proteins on self-assembled peptide nanofibrils is accomplished by noncovalent attachment using a split-protein strategy.

Peptidic Biomaterials: From Self-Assembling to Regenerative Medicine

Peptidic biomaterials represent a particularly exciting topic in regenerative medicine. Peptidic scaffolds can be specifically designed for biomimetic customization for targeted therapy. The field is at a pivotal point where preclinical research is being translated into clinics, so it is crucial to understand the theory and describe the status of this rapidly developing technology. In this review, we highlight major advantages and current limitations of self-assembling peptide-based biomaterials, and we discuss the most widely used classes of assembling peptides, describing recent and promising approaches in tissue engineering, drug delivery, and clinics. We also suggest design strategies and hurdles that still need to be overcome to fully exploit their therapeutic potential.

Nanoparticle transport across the blood brain barrier

While the role of the blood-brain barrier (BBB) is increasingly recognized in the (development of treatments targeting neurodegenerative disorders, to date, few strategies exist that enable drug delivery of non-BBB crossing molecules directly to their site of action, the brain. However, the recent advent of Nanomedicines may provide a potent tool to implement CNS targeted delivery of active compounds. Approaches for BBB crossing are deeply investigated in relation to the pathology: among the main important diseases of the CNS, this review focuses on the application of nanomedicines to neurodegenerative disorders (Alzheimer, Parkinson and Huntington's Disease) and to other brain pathologies as epilepsy, infectious diseases, multiple sclerosis, lysosomal storage disorders, strokes.

Functional Self-Assembling Peptide Nanofiber Hydrogels Designed for Nerve Degeneration

Self-assembling peptide (SAP) RADA16-I (Ac-(RADA)4-CONH2) has been suffering from a main drawback associated with low pH, which damages cells and host tissues upon direct exposure. In this study, we presented a strategy to prepare nanofiber hydrogels from two designer SAPs at neutral pH. RADA16-I was appended with functional motifs containing cell adhesion peptide RGD and neurite outgrowth peptide IKVAV. The two SAPs were specially designed to have opposite net charges at neutral pH, the combination of which created a nanofiber hydrogel (-IKVAV/-RGD) characterized by significantly higher G' than G″ in a viscoelasticity examination. Circular dichroism, Fourier transform infrared spectroscopy, and Raman measurements were performed to investigate the secondary structure of the designer SAPs, indicating that both the hydrophobic/hydrophilic properties and electrostatic interactions of the functional motifs play an important role in the self-assembling behavior of the designer SAPs. The neural progenitor cells (NPCs)/stem cells (NSCs) fully embedded in the 3D-IKVAV/-RGD nanofiber hydrogel survived, whereas those embedded within the RADA 16-I hydrogel hardly survived. Moreover, the -IKVAV/-RGD nanofiber hydrogel supported NPC/NSC neuron and astrocyte differentiation in a 3D environment without adding extra growth factors. Studies of three nerve injury models, including sciatic nerve defect, intracerebral hemorrhage, and spinal cord transection, indicated that the designer -IKVAV/-RGD nanofiber hydrogel provided a more permissive environment for nerve regeneration than the RADA 16-I hydrogel. Therefore, we reported a new mechanism that might be beneficial for the synthesis of SAPs for in vitro 3D cell culture and nerve regeneration.

Peptide nanofiber complexes with siRNA for deep brain gene silencing by stereotactic neurosurgery

Peptide nanofibers (PNFs) are one-dimensional assemblies of amphiphilic peptides in a cylindrical geometry. We postulated that peptide nanofibers (PNFs) can provide the tools for genetic intervention and be used for delivery of siRNA, as they can be engineered with positively charged amino acids that can electrostatically bind siRNA. The aim of this work was to investigate the use of PNFs as vectors for siRNA delivery providing effective gene knockdown. We designed a surfactant-like peptide (palmitoyl-GGGAAAKRK) able to self-assemble into PNFs and demonstrated that complexes of PNF:siRNA are uptaken intracellularly and increase the residence time of siRNA in the brain after intracranial administration. The biological activity of the complexes was investigated in vitro by analyzing the down-regulation of the expression of a targeted protein (BCL2), as well as induction of apoptosis, as well as in vivo by analyzing the relative gene expression upon stereotactic administration into a deep rat brain structure (the subthalamic nucleus). Gene expression levels of BCL2 mRNA showed that PNF:siBCL2 constructs were able to silence the target BCL2 in specific loci of the brain. Silencing of the BCL2 gene resulted in ablation of neuronal cell populations, indicating that genetic interventions by PNF:siRNA complexes may lead to novel treatment strategies of CNS pathologies.