Traumatic brain injury opens blood–brain barrier to stealth liposomes via an enhanced permeability and retention (EPR)-like effect

Reprograming Clots for In Vivo Chemical Targeting in Traumatic Brain Injury

Traumatic brain injury (TBI) is a critical public health concern, yet there are no therapeutics available to improve long-term outcomes. Drug delivery to TBI remains a challenge due to the blood-brain barrier and increased intracranial pressure. In this work, a chemical targeting approach to improve delivery of materials to the injured brain, is developed. It is hypothesized that the provisional fibrin matrix can be harnessed as an injury-specific scaffold that can be targeted by materials via click chemistry. To accomplish this, the brain clot is engineered in situ by delivering fibrinogen modified with strained cyclooctyne (SCO) moieties, which incorporated into the injury lesion and is retained there for days. Improved intra-injury capture and retention of diverse, clickable azide-materials including a small molecule azide-dye, 40 kDa azide-PEG nanomaterial, and a therapeutic azide-protein in multiple dosing regimens is subsequently observed. To demonstrate therapeutic translation of this approach, a reduction in reactive oxygen species levels in the injured brain after delivery of the antioxidant catalase, is achieved. Further, colocalization between azide and SCO-fibrinogen is specific to the brain over off-target organs. Taken together, a chemical targeting strategy leveraging endogenous clot formation is established which can be applied to improve therapeutic delivery after TBI.

Advantages of nanocarriers for basic research in the field of traumatic brain injury

A major challenge for the efficient treatment of traumatic brain injury is the need for therapeutic molecules to cross the blood-brain barrier to enter and accumulate in brain tissue. To overcome this problem, researchers have begun to focus on nanocarriers and other brain-targeting drug delivery systems. In this review, we summarize the epidemiology, basic pathophysiology, current clinical treatment, the establishment of models, and the evaluation indicators that are commonly used for traumatic brain injury. We also report the current status of traumatic brain injury when treated with nanocarriers such as liposomes and vesicles. Nanocarriers can overcome a variety of key biological barriers, improve drug bioavailability, increase intracellular penetration and retention time, achieve drug enrichment, control drug release, and achieve brain-targeting drug delivery. However, the application of nanocarriers remains in the basic research stage and has yet to be fully translated to the clinic.

Colloidal therapeutics in the management of traumatic brain injury: Portray of biomarkers and drug-targets, preclinical and clinical pieces of evidence and future prospects

Complexity associated with the aberrant physiology of traumatic brain injury (TBI) makes its therapeutic targeting vulnerable. The underlying mechanisms of pathophysiology of TBI are yet to be completely illustrated. Primary injury in TBI is associated with contusions and axonal shearing whereas excitotoxicity, mitochondrial dysfunction, free radicals generation, and neuroinflammation are considered under secondary injury. MicroRNAs, proinflammatory cytokines, and Glial fibrillary acidic protein (GFAP) recently emerged as biomarkers in TBI. In addition, several approved therapeutic entities have been explored to target existing and newly identified drug-targets in TBI. However, drug delivery in TBI is hampered due to disruption of blood-brain barrier (BBB) in secondary TBI, as well as inadequate drug-targeting and retention effect. Colloidal therapeutics appeared helpful in providing enhanced drug availability to the brain owing to definite targeting strategies. Moreover, immense efforts have been put together to achieve increased bioavailability of therapeutics to TBI by devising effective targeting strategies. The potential of colloidal therapeutics to efficiently deliver drugs at the site of injury and down-regulate the mediators of TBI are serving as novel policies in the management of TBI. Therefore, in present manuscript, we have illuminated a myriad of molecular-targets currently identified and recognized in TBI. Moreover, particular emphasis is given to frame armamentarium of repurpose drugs which could be utilized to block molecular targets in TBI in addition to drug delivery barriers. The critical role of colloidal therapeutics such as liposomes, nanoparticles, dendrimers, and exosomes in drug delivery to TBI through invasive and non-invasive routes has also been highlighted.

Infusible Extracellular Matrix Biomaterial Promotes Vascular Integrity and Modulates the Inflammatory Response in Acute Traumatic Brain Injury

Traumatic brain injury (TBI) affects millions of people each year and, in many cases, results in long-term disabilities. Once a TBI has occurred, there is a significant breakdown of the blood-brain barrier resulting in increased vascular permeability and progression of the injury. In this study, the use of an infusible extracellular matrix-derived biomaterial (iECM) for its ability to reduce vascular permeability and modulate gene expression in the injured brain is investigated. First, the pharmacokinetics of iECM administration in a mouse model of TBI is characterized, and the robust accumulation of iECM at the site of injury is demonstrated. Next, it is shown that iECM administration after injury can reduce the extravasation of molecules into the brain, and in vitro, iECM increases trans-endothelial electrical resistance across a monolayer of TNFα-stimulated endothelial cells. In gene expression analysis of brain tissue, iECM induces changes that are indicative of downregulation of the proinflammatory response 1-day post-injury/treatment and neuroprotection at 5 days post-injury/treatment. Therefore, iECM shows potential as a treatment for TBI.

An Activity-Based Nanosensor for Minimally-Invasive Measurement of Protease Activity in Traumatic Brain Injury

Current screening and diagnostic tools for traumatic brain injury (TBI) have limitations in sensitivity and prognostication. Aberrant protease activity is a central process that drives disease progression in TBI and is associated with worsened prognosis; thus direct measurements of protease activity could provide more diagnostic information. In this study, a nanosensor is engineered to release a measurable signal into the blood and urine in response to activity from the TBI-associated protease calpain. Readouts from the nanosensor were designed to be compatible with ELISA and lateral flow assays, clinically-relevant assay modalities. In a mouse model of TBI, the nanosensor sensitivity is enhanced when ligands that target hyaluronic acid are added. In evaluation of mice with mild or severe injuries, the nanosensor identifies mild TBI with a higher sensitivity than the biomarker GFAP. This nanosensor technology allows for measurement of TBI-associated proteases without the need to directly access brain tissue, and has the potential to complement existing TBI diagnostic tools.

Analysis of PEG-lipid anchor length on lipid nanoparticle pharmacokinetics and activity in a mouse model of traumatic brain injury

Traumatic brain injury (TBI) affects millions of people worldwide, yet there are currently no therapeutics that address the long-term impairments that develop in a large portion of survivors. Lipid nanoparticles (LNPs) are a promising therapeutic strategy that may address the molecular basis of TBI pathophysiology. LNPs are the only non-viral gene delivery platform to achieve clinical success, but systemically administered formulations have only been established for targets in the liver. In this work, we evaluated the pharmacokinetics and activity of LNPs formulated with polyethylene glycol (PEG)-lipids of different anchor lengths when systemically administered to a mouse model of TBI. We observed an increase in LNP accumulation and activity in the injured brain hemisphere compared to the uninjured contralateral brain hemisphere. Interestingly, transgene expression mediated by LNPs was more durable in injured brain tissue compared to off-target organs when compared between 4 and 24 hours. The PEG-lipid is an important component of LNP formulation necessary for the stable formation and storage of LNPs, but the PEG-lipid structure and content also has an impact on LNP function. LNP formulations containing various ratios of PEG-lipid with C18 (DSPE-PEG) and C14 (DMG-PEG) anchors displayed similar physicochemical properties, independent of the PEG-lipid compositions. As the proportion of DSPE-PEG was increased in formulations, blood circulation times of LNPs increased and the duration of expression increased. We also evaluated diffusion of LNPs after convection enhanced delivery (CED) in healthy brains and found LNPs distributed >1 mm away from the injection site. Understanding LNP pharmacokinetics and activity in TBI models and the impact of PEG-lipid anchor length informs the design of LNP-based therapies for TBI after systemic administration.

Engineered nanomaterials that exploit blood-brain barrier dysfunction fordelivery to the brain

The blood-brain barrier (BBB) is a highly regulated physical and functional boundarythat tightly controls the transport of materials between the blood and the brain. There is an increasing recognition that the BBB is dysfunctional in a wide range of neurological disorders; this dysfunction can be symptomatic of the disease but can also play a role in disease etiology. BBB dysfunction can be exploited for the delivery of therapeutic nanomaterials. Forexample, there can be a transient, physical disruption of the BBB in diseases such as brain injury and stroke, which allows temporary access of nanomaterials into the brain. Physicaldisruption of the BBB through external energy sources is now being clinically pursued toincrease therapeutic delivery into the brain. In other diseases, the BBB takes on new properties that can beleveraged by delivery carriers. For instance, neuroinflammation induces the expression ofreceptors on the BBB that can be targeted by ligand-modified nanomaterials and theendogenous homing of immune cells into the diseased brain can be hijacked for the delivery ofnanomaterials. Lastly, BBB transport pathways can be altered to increase nanomaterial transport. In this review, we will describe changes that can occur in the BBB in disease, and how these changes have been exploited by engineered nanomaterials forincreased transport into the brain.

Sex-based differences of antioxidant enzyme nanoparticle effects following traumatic brain injury

Following traumatic brain injury (TBI), reactive oxygen species (ROS) are released in excess, causing oxidative stress, carbonyl stress, and cell death, which induce the additional release of ROS. The limited accumulation and retention of small molecule antioxidants commonly used in clinical trials likely limit the target engagement and therapeutic effect in reducing secondary injury. Small molecule drugs also need to be administered every several hours to maintain bioavailability in the brain. Therefore, there is a need for a burst and sustained release system with high accumulation and retention in the injured brain. Here, we utilized Pro-NP™ with a size of 200 nm, which was designed to have a burst and sustained release of encapsulated antioxidants, Cu/Zn superoxide dismutase (SOD1) and catalase (CAT), to scavenge ROS for >24 h post-injection. Here, we utilized a controlled cortical impact (CCI) mouse model of TBI and found the accumulation of Pro-NP™ in the brain lesion was highest when injected immediately after injury, with a reduction in the accumulation with delayed administration of 1 h or more post-injury. Pro-NP™ treatment with 9000 U/kg SOD1 and 9800 U/kg CAT gave the highest reduction in ROS in both male and female mice. We found that Pro-NP™ treatment was effective in reducing carbonyl stress and necrosis at 1 d post-injury in the contralateral hemisphere in male mice, which showed a similar trend to untreated female mice. Although we found that male and female mice similarly benefit from Pro-NP™ treatment in reducing ROS levels 4 h post-injury, Pro-NP™ treatment did not significantly affect markers of post-traumatic oxidative stress in female CCI mice as compared to male CCI mice. These findings of protection by Pro-NP™ in male mice did not extend to 7 d post-injury, which suggests subsequent treatments with Pro-NP™ may be needed to afford protection into the chronic phase of injury. Overall, these different treatment effects of Pro-NP™ between male and female mice suggest important sex-based differences in response to antioxidant nanoparticle delivery and that there may exist a maximal benefit from local antioxidant activity in injured brain.

Recent advances in nanomaterials for the treatment of spinal cord injury

Spinal cord injuries (SCIs) are devastating. In SCIs, a powerful traumatic force impacting the spinal cord results in the permanent loss of nerve function below the injury level, leaving the patient paralyzed and wheelchair-bound for the remainder of his/her life. Unfortunately, clinical treatment that depends on surgical decompression appears to be unable to handle damaged nerves, and high-dose methylprednisolone-based therapy is also associated with problems, such as infection, gastrointestinal bleeding, femoral head necrosis, obesity, and hyperglycemia. Nanomaterials have opened new avenues for SCI treatment. Among them, performance-based nanomaterials derived from a variety of materials facilitate improvements in the microenvironment of traumatic injury and, in some cases, promote neuron regeneration. Nanoparticulate drug delivery systems enable the optimization of drug effects and drug bioavailability, thus contributing to the development of novel treatments. The improved efficiency and accuracy of gene delivery will also benefit the exploration of SCI mechanisms and the understanding of key genes and signaling pathways. Herein, we reviewed different types of nanomaterials applied to the treatment of SCI and summarized their functions and advantages to provide new perspectives for future clinical therapies.

Porous Silicon Nanoparticles Targeted to the Extracellular Matrix for Therapeutic Protein Delivery in Traumatic Brain Injury

Traumatic brain injury (TBI) is a major cause of disability and death among children and young adults in the United States, yet there are currently no treatments that improve the long-term brain health of patients. One promising therapeutic for TBI is brain-derived neurotrophic factor (BDNF), a protein that promotes neurogenesis and neuron survival. However, outstanding challenges to the systemic delivery of BDNF are its instability in blood, poor transport into the brain, and short half-life in circulation and brain tissue. Here, BDNF is encapsulated into an engineered, biodegradable porous silicon nanoparticle (pSiNP) in order to deliver bioactive BDNF to injured brain tissue after TBI. The pSiNP carrier is modified with the targeting ligand CAQK, a peptide that binds to extracellular matrix components upregulated after TBI. The protein cargo retains bioactivity after release from the pSiNP carrier, and systemic administration of the CAQK-modified pSiNPs results in effective delivery of the protein cargo to injured brain regions in a mouse model of TBI. When administered after injury, the CAQK-targeted pSiNP delivery system for BDNF reduces lesion volumes compared to free BDNF, supporting the hypothesis that pSiNPs mediate therapeutic protein delivery after systemic administration to improve outcomes in TBI.

The Role of Fibrinolytic System in Health and Disease

The fibrinolytic system is composed of the protease plasmin, its precursor plasminogen and their respective activators, tissue-type plasminogen activator (tPA) and urokinase-type plasminogen activator (uPA), counteracted by their inhibitors, plasminogen activator inhibitor type 1 (PAI-1), plasminogen activator inhibitor type 2 (PAI-2), protein C inhibitor (PCI), thrombin activable fibrinolysis inhibitor (TAFI), protease nexin 1 (PN-1) and neuroserpin. The action of plasmin is counteracted by α2-antiplasmin, α2-macroglobulin, TAFI, and other serine protease inhibitors (antithrombin and α2-antitrypsin) and PN-1 (protease nexin 1). These components are essential regulators of many physiologic processes. They are also involved in the pathogenesis of many disorders. Recent advancements in our understanding of these processes enable the opportunity of drug development in treating many of these disorders.

Size-Selective Transfer of Lipid Nanoparticle-Based Drug Carriers Across the Blood Brain Barrier Via Vascular Occlusions Following Traumatic Brain Injury

The current lack of understanding about how nanocarriers cross the blood-brain barrier (BBB) in the healthy and injured brain is hindering the clinical translation of nanoscale brain-targeted drug-delivery systems. Here, the bio-distribution of lipid nano-emulsion droplets (LNDs) of two sizes (30 and 80 nm) in the mouse brain after traumatic brain injury (TBI) is investigated. The highly fluorescent LNDs are prepared by loading them with octadecyl rhodamine B and a bulky hydrophobic counter-ion, tetraphenylborate. Using in vivo two-photon and confocal imaging, the circulation kinetics and bio-distribution of LNDs in the healthy and injured mouse brain are studied. It is found that after TBI, LNDs of both sizes accumulate at vascular occlusions, where specifically 30 nm LNDs extravasate into the brain parenchyma and reach neurons. The vascular occlusions are not associated with bleedings, but instead are surrounded by processes of activated microglia, suggesting a specific opening of the BBB. Finally, correlative light-electron microscopy reveals 30 nm LNDs in endothelial vesicles, while 80 nm particles remain in the vessel lumen, indicating size-selective vesicular transport across the BBB via vascular occlusions. The data suggest that microvascular occlusions serve as "gates" for the transport of nanocarriers across the BBB.

Strategies to improve the EPR effect: A mechanistic perspective and clinical translation

Many efforts have been made to achieve targeted delivery of anticancer drugs to enhance their efficacy and to reduce their adverse effects. These efforts include the development of nanomedicines as they can selectively penetrate through tumor blood vessels through the enhanced permeability and retention (EPR) effect. The EPR effect was first proposed by Maeda and co-workers in 1986, and since then various types of nanoparticles have been developed to take advantage of the phenomenon with regards to drug delivery. However, the EPR effect has been found to be highly variable and thus unreliable due to the complex tumor microenvironment. Various physical and pharmacological strategies have been explored to overcome this challenge. Here, we review key advances and emerging concepts of such EPR-enhancing strategies. Furthermore, we analyze 723 clinical trials of nanoparticles with EPR enhancers and discuss their clinical translation.

Minocycline-Loaded Poly(α-Lipoic Acid)-Methylprednisolone Prodrug Nanoparticles for the Combined Anti-Inflammatory Treatment of Spinal Cord Injury

Purpose

Traumatic spinal cord injury (TSCI) induces a powerful inflammatory response that can significantly exacerbate the extent and severity of neural damage (termed as “secondary injury”). Thus, the suppression of inflammation is crucial for reducing neurological dysfunction following TSCI. However, the conventional anti-inflammatory drugs show limited efficacy because of poor penetration and release kinetics at the injury site. This study describes the design, synthesis, release kinetics, biosafety, and preclinical efficacy of minocycline (MC)-loaded poly(α-lipoic acid)–methylprednisolone (PαLA-MP) prodrug nanoparticles (NPs) for the combined anti-inflammatory treatment of TSCI.

Methods

NPs were produced by conjugating MP to PαLA and then loading MC. The NP structure was confirmed through ¹H nuclear magnetic resonance (¹H NMR), Fourier transform infrared spectroscopy, ultraviolet–visible absorption spectroscopy, gel permeation chromatography, dynamic light scattering, and transmission electron microscopy. Drug-loading content and efficacy were measured using high-performance liquid chromatography (HPLC) or ¹H NMR and release kinetics through HPLC. Biosafety was examined using the MTT assay, cell penetration efficiency using confocal microscopy, and flow cytometry using Cyanine5 (Cy5)-labeled MC-PαLA-MP NPs, effects on injury-induced pro-inflammatory cytokine release using enzyme-linked immunosorbent assays and immunofluorescence, and treatment efficacy by measuring motor recovery in a rat model of TSCI.

Results

The MC-PαLA-MP NPs exhibited high biocompatibility and released 81% MC and 54% MP within 24 h under TSCI-like conditions, effectively reducing 40% of pro-inflammatory cytokine release both in cultures and injured rat spinal cord tissues. Systemic injection increased the Basso, Beattie, Bresnahan score of TSCI rats from 2.33 ± 0.52 to 8.83 ± 1.83 in 8 weeks, providing effective neuroprotection and enhanced exercise recovery in the TSCI rats.

Conclusion

The MC-PαLA-MP NPs can mitigate secondary inflammation and preserve motor function following experimental TSCI, which suggests their potential for clinical application.

Targeting the Extracellular Matrix in Traumatic Brain Injury Increases Signal Generation from an Activity-Based Nanosensor

Traumatic brain injury (TBI) is a critical public health concern and major contributor to death and long-term disability. After the initial trauma, a sustained secondary injury involving a complex continuum of pathophysiology unfolds, ultimately leading to the destruction of nervous tissue. One disease hallmark of TBI is ectopic protease activity, which can mediate cell death, extracellular matrix breakdown, and inflammation. We previously engineered a fluorogenic activity-based nanosensor for TBI (TBI-ABN) that passively accumulates in the injured brain across the disrupted vasculature and generates fluorescent signal in response to calpain-1 cleavage, thus enabling in situ visualization of TBI-associated calpain-1 protease activity. In this work, we hypothesized that actively targeting the extracellular matrix (ECM) of the injured brain would improve nanosensor accumulation in the injured brain beyond passive delivery alone and lead to increased nanosensor activation. We evaluated several peptides that bind exposed/enriched ECM constituents in the brain and discovered that nanomaterials modified with peptides that target hyaluronic acid (HA) displayed widespread distribution across the injury lesion, in particular colocalizing with perilesional and hippocampal neurons. Modifying TBI-ABN with HA-targeting peptide led to increases in activation in a ligand-valency-dependent manner, up to 6.6-fold in the injured cortex compared to a nontargeted nanosensor. This robust nanosensor activation enabled 3D visualization of injury-specific protease activity in a cleared and intact brain. In our work, we establish that targeting brain ECM with peptide ligands can be leveraged to improve the distribution and function of a bioresponsive imaging nanomaterial.

Claudin-1-Targeted Nanoparticles for Delivery to Aging-Induced Alterations in the Blood-Brain Barrier

Aging-induced alterations to the blood-brain barrier (BBB) are increasingly being seen as a primary event in chronic progressive neurological disorders that lead to cognitive decline. With the goal of increasing delivery into the brain in hopes of effectively treating these diseases, a large focus has been placed on developing BBB permeable materials. However, these strategies have suffered from a lack of specificity toward regions of disease progression. Here, we report on the development of a nanoparticle (C1C2-NP) that targets regions of increased claudin-1 expression that reduces BBB integrity. Using dynamic contrast enhanced magnetic resonance imaging, we find that C1C2-NP accumulation and retention is significantly increased in brains from 12 month-old mice as compared to nontargeted NPs and brains from 2 month-old mice. Furthermore, we find C1C2-NP accumulation in brain endothelial cells with high claudin-1 expression, suggesting target-specific binding of the NPs, which was validated through fluorescence imaging, in vitro testing, and biophysical analyses. Our results further suggest a role of claudin-1 in reducing BBB integrity during aging and show altered expression of claudin-1 can be actively targeted with NPs. These findings could help develop strategies for longitudinal monitoring of tight junction protein expression changes during aging as well as be used as a delivery strategy for site-specific delivery of therapeutics at these early stages of disease development.

Pharmacokinetic Analysis of Peptide-Modified Nanoparticles with Engineered Physicochemical Properties in a Mouse Model of Traumatic Brain Injury

Peptides are used to control the pharmacokinetic profiles of nanoparticles due to their ability to influence tissue accumulation and cellular interactions. However, beyond the study of specific peptides, there is a lack of understanding of how peptide physicochemical properties affect nanoparticle pharmacokinetics, particularly in the context of traumatic brain injury (TBI). We engineered nanoparticle surfaces with peptides that possess a range of physicochemical properties and evaluated their distribution after two routes of administration: direct injection into a healthy mouse brain and systemic delivery in a mouse model of TBI. In both administration routes, we found that peptide-modified nanoparticle pharmacokinetics were influenced by the charge characteristics of the peptide. When peptide-modified nanoparticles are delivered directly into the brain, nanoparticles modified with positively charged peptides displayed restricted distribution from the injection site compared to nanoparticles modified with neutral, zwitterionic, or negatively charged peptides. After intravenous administration in a TBI mouse model, positively charged peptide-modified nanoparticles accumulated more in off-target organs, including the heart, lung, and kidneys, than zwitterionic, neutral, or negatively charged peptide-modified nanoparticles. The increase in off-target organ accumulation of positively charged peptide-modified nanoparticles was concomitant with a relative decrease in accumulation in the injured brain compared to zwitterionic, neutral, or negatively charged peptide-modified nanoparticles. Understanding how nanoparticle pharmacokinetics are influenced by the physicochemical properties of peptides presented on the nanoparticle surface is relevant to the development of nanoparticle-based TBI therapeutics and broadly applicable to nanotherapeutic design, including synthetic nanoparticles and viruses.

Evolution of blood-brain barrier in brain diseases and related systemic nanoscale brain-targeting drug delivery strategies

Blood–brain barrier (BBB) strictly controls matter exchange between blood and brain, and severely limits brain penetration of systemically administered drugs, resulting in ineffective drug therapy of brain diseases. However, during the onset and progression of brain diseases, BBB alterations evolve inevitably. In this review, we focus on nanoscale brain-targeting drug delivery strategies designed based on BBB evolutions and related applications in various brain diseases including Alzheimer's disease, Parkinson's disease, epilepsy, stroke, traumatic brain injury and brain tumor. The advances on optimization of small molecules for BBB crossing and non-systemic administration routes (e.g., intranasal treatment) for BBB bypassing are not included in this review.

Highlighting the usage of polymeric nanoparticles for the treatment of traumatic brain injury: A review study

There are very limited options for treating traumatic brain injury (TBI). Nanoparticles offer the potential of targeting specific cell types, and, potentially, crossing the BBB under the right conditions making them an area of active research for treating TBI. This review focuses on polymeric nanoparticles and the impact of their chemistry, size, and surface groups on their interactions with the vasculature and cells of the brain following injury. The vast majority of the work in the field focuses on acute injury, and when the work is looked at closely, it suggests that nanoparticles rely on interactions with vascular and immune cells to alter the environment of the brain. Nonetheless, there are promising results from a number of approaches that lead to behavioral improvements coupled with neuroprotection that offer promise for therapeutic outcomes. The majority of approaches have been tested immediately following injury. It is not entirely clear what impact these approaches will have in chronic TBI, but being able to modulate inflammation specifically may have a role both during and after the acute phase of injury.

Stabilized albumin coatings on engineered xenografts for attenuation of acute immune and inflammatory responses

Xenogeneic grafts are promising candidates for transplantation therapy due to their easily accessible sources. Nevertheless, the immune and inflammatory responses induced by xenografts need to be addressed for clinical use. A novel and facile method was introduced for the attenuation of immune and inflammatory responses by extending the immune evasion potential of albumin to the tissue engineering field and coating albumin, which could passivate biomaterial surfaces, onto xenografts. Albumin was first modified by dopamine to enhance its adhesion on graft surfaces. Porcine chondrocytes derived living hyaline cartilage graft (LhCG) and decellularized LhCG (dLhCG) were applied as xenograft models implanted in the omentum of rats. Both LhCG which contained porcine chondrocytes as well as secreted ECM and dLhCG which was mainly composed of the porcine source ECM showed alleviated immune and inflammatory responses after being coated with albumin at cell, protein and gene levels, respectively. Significantly less inflammatory cells including neutrophils, macrophages and lymphocytes were recruited according to pathological analysis and immunohistochemistry staining with lower gene expression encoding inflammation-related cytokines including MCP-1, IL-6 and IL-1β after employing LhCG and dLhCG with albumin passivation coating.

Nanomedicine for Acute Brain Injuries: Insight from Decades of Cancer Nanomedicine

Acute brain injuries such as traumatic brain injury and stroke affect 85 million people a year worldwide, and many survivors suffer from long-term physical, cognitive, or psychosocial impairments. There are few FDA-approved therapies that are effective at preventing, halting, or ameliorating the state of disease in the brain after acute brain injury. To address this unmet need, one potential strategy is to leverage the unique physical and biological properties of nanomaterials. Decades of cancer nanomedicine research can serve as a blueprint for innovation in brain injury nanomedicines, both to emulate the successes and also to avoid potential pitfalls. In this review, we discuss how shared disease physiology between cancer and acute brain injuries can inform the design of novel nanomedicines for acute brain injuries. These disease hallmarks include dysregulated vasculature, an altered microenvironment, and changes in the immune system. We discuss several nanomaterial strategies that can be engineered to exploit these disease hallmarks, for example, passive accumulation, active targeting of disease-associated signals, bioresponsive designs that are "smart", and immune interactions.

Towards precision nanomedicine for cerebrovascular diseases with emphasis on Cerebral Cavernous Malformation (CCM)

Introduction: Cerebrovascular diseases encompass various disorders of the brain vasculature, such as ischemic/hemorrhagic strokes, aneurysms, and vascular malformations, also affecting the central nervous system leading to a large variety of transient or permanent neurological disorders. They represent major causes of mortality and long-term disability worldwide, and some of them can be inherited, including Cerebral Cavernous Malformation (CCM), an autosomal dominant cerebrovascular disease linked to mutations in CCM1/KRIT1, CCM2, or CCM3/PDCD10 genes.Areas covered: Besides marked clinical and etiological heterogeneity, some commonalities are emerging among distinct cerebrovascular diseases, including key pathogenetic roles of oxidative stress and inflammation, which are increasingly recognized as major disease hallmarks and therapeutic targets. This review provides a comprehensive overview of the different clinical features and common pathogenetic determinants of cerebrovascular diseases, highlighting major challenges, including the pressing need for new diagnostic and therapeutic strategies, and focusing on emerging innovative features and promising benefits of nanomedicine strategies for early detection and targeted treatment of such diseases.Expert opinion: Specifically, we describe and discuss the multiple physico-chemical features and unique biological advantages of nanosystems, including nanodiagnostics, nanotherapeutics, and nanotheranostics, that may help improving diagnosis and treatment of cerebrovascular diseases and neurological comorbidities, with an emphasis on CCM disease.

Slow blood-to-brain transport underlies enduring barrier dysfunction in American football players

Repetitive mild traumatic brain injury in American football players has garnered increasing public attention following reports of chronic traumatic encephalopathy, a progressive tauopathy. While the mechanisms underlying repetitive mild traumatic brain injury-induced neurodegeneration are unknown and antemortem diagnostic tests are not available, neuropathology studies suggest a pathogenic role for microvascular injury, specifically blood–brain barrier dysfunction. Thus, our main objective was to demonstrate the effectiveness of a modified dynamic contrast-enhanced MRI approach we have developed to detect impairments in brain microvascular function. To this end, we scanned 42 adult male amateur American football players and a control group comprising 27 athletes practicing a non-contact sport and 26 non-athletes. MRI scans were also performed in 51 patients with brain pathologies involving the blood–brain barrier, namely malignant brain tumours, ischaemic stroke and haemorrhagic traumatic contusion. Based on data from prolonged scans, we generated maps that visualized the permeability value for each brain voxel. Our permeability maps revealed an increase in slow blood-to-brain transport in a subset of amateur American football players, but not in sex- and age-matched controls. The increase in permeability was region specific (white matter, midbrain peduncles, red nucleus, temporal cortex) and correlated with changes in white matter, which were confirmed by diffusion tensor imaging. Additionally, increased permeability persisted for months, as seen in players who were scanned both on- and off-season. Examination of patients with brain pathologies revealed that slow tracer accumulation characterizes areas surrounding the core of injury, which frequently shows fast blood-to-brain transport. Next, we verified our method in two rodent models: rats and mice subjected to repeated mild closed-head impact injury, and rats with vascular injury inflicted by photothrombosis. In both models, slow blood-to-brain transport was observed, which correlated with neuropathological changes. Lastly, computational simulations and direct imaging of the transport of Evans blue-albumin complex in brains of rats subjected to recurrent seizures or focal cerebrovascular injury suggest that increased cellular transport underlies the observed slow blood-to-brain transport. Taken together, our findings suggest dynamic contrast-enhanced-MRI can be used to diagnose specific microvascular pathology after traumatic brain injury and other brain pathologies.

Protein kinase inhibitors in traumatic brain injury and repair: New roles of nanomedicine

Traumatic brain injury (TBI) causes physical injury to the cell membranes of neurons, glial and axons causing the release of several neurochemicals including glutamate and cytokines altering cell-signaling pathways. Upregulation of mitogen associated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) occurs that is largely responsible for cell death. The pharmacological blockade of these pathways results in cell survival. In this review role of several protein kinase inhibitors on TBI induced oxidative stress, blood-brain barrier breakdown, brain edema formation, and resulting brain pathology is discussed in the light of current literature.

Ultrasmall Mixed Eu-Gd Oxide Nanoparticles for Multimodal Fluorescence and Magnetic Resonance Imaging of Passive Accumulation and Retention in TBI

Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. TBI can have a long-term impact on the quality of life for survivors of all ages. However, there remains no approved treatment that improves outcomes following TBI, which is partially due to poor delivery of therapies into the brain. Therefore, there is a significant unmet need to develop more effective delivery strategies that increase the accumulation and retention of potentially efficacious treatments in the injured brain. Recent work has revealed that nanoparticles (NPs) may offer a promising approach for site-specific delivery; however, a detailed understanding of the specific NP properties that promote brain accumulation and retention are still being developed. Multimodal imaging plays a vital role in the understanding of physicochemical properties that initiate the uptake and accumulation of NPs in the brain at both high spatial (e.g., fluorescence imaging) and temporal (e.g., magnetic resonance imaging, MRI) frequency. However, many NP systems that are currently used in TBI only provide contrast in a single imaging modality limiting the imaging data that can be obtained, and those that offer multimodal imaging capabilities have complicated multistep synthesis methods. Therefore, the goal of this work was to develop an ultrasmall NP with simple fabrication capable of multimodal imaging. Here, we describe the development, characterization, accumulation, and retention of poly(ethylene glycol) (PEG)-coated europium-gadolinium (Eu-Gd) mixed magnetic NPs (MNPs) in a controlled cortical impact mouse model of TBI. We find that these NPs having an ultrasmall core size of 2 nm and a small hydrodynamic size of 13.5 nm can be detected in both fluorescence and MR imaging modalities and rapidly accumulate and are retained in injured brain parenchyma. These NPs should allow for further testing of NP physicochemical properties that promote accumulation and retention in TBI and other disease models.

An Activity-Based Nanosensor for Traumatic Brain Injury

Currently, traumatic brain injury (TBI) is detected by medical imaging; however, medical imaging requires expensive capital equipment, is time- and resource-intensive, and is poor at predicting patient prognosis. To date, direct measurement of elevated protease activity has yet to be utilized to detect TBI. In this work, we engineered an activity-based nanosensor for TBI (TBI-ABN) that responds to increased protease activity initiated after brain injury. We establish that a calcium-sensitive protease, calpain-1, is active in the injured brain hours within injury. We then optimize the molecular weight of a nanoscale polymeric carrier to infiltrate into the injured brain tissue with minimal renal filtration. A calpain-1 substrate that generates a fluorescent signal upon cleavage was attached to this nanoscale polymeric carrier to generate an engineered TBI-ABN. When applied intravenously to a mouse model of TBI, our engineered sensor is observed to locally activate in the injured brain tissue. This TBI-ABN is the first demonstration of a sensor that responds to protease activity to detect TBI.

Evaluating differential nanoparticle accumulation and retention kinetics in a mouse model of traumatic brain injury via Ktrans mapping with MRI

Traumatic brain injury (TBI) is a leading cause of injury-related death worldwide, yet there are no approved neuroprotective therapies that improve neurological outcome post-injury. Transient opening of the blood-brain barrier following injury provides an opportunity for passive accumulation of intravenously administered nanoparticles through an enhanced permeation and retention-like effect. However, a thorough understanding of physicochemical properties that promote optimal uptake and retention kinetics in TBI is still needed. In this study, we present a robust method for magnetic resonance imaging of nanoparticle uptake and retention kinetics following intravenous injection in a controlled cortical impact mouse model of TBI. Three contrast-enhancing nanoparticles with different hydrodynamic sizes and relaxivity properties were compared. Accumulation and retention were monitored by modelling the permeability coefficient, K^trans, for each nanoparticle within the reproducible mouse model. Quantification of K^trans for different nanoparticles allowed for non-invasive, multi-time point assessment of both accumulation and retention kinetics in the injured tissue. Using this method, we found that 80 nm poly(lactic-co-glycolic acid) nanoparticles had maximal K^trans in a TBI when injected 3 hours post-injury, showing significantly higher accumulation kinetics than the small molecule, Gd-DTPA. This robust method will enable optimization of administration time and nanoparticle physicochemical properties to achieve maximum delivery.

A Role for Nanoparticles in Treating Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the main causes of disability in children and young adults, as well as a significant concern for elderly individuals. Depending on the severity, TBI can have a long-term impact on the quality of life for survivors of all ages. The primary brain injury can result in severe disability or fatality, and secondary brain damage can increase the complexities in cellular, inflammatory, neurochemical, and metabolic changes in the brain, which can last decades post-injury. Thus, survival from a TBI is often accompanied by lifelong disabilities. Despite the significant morbidity, mortality, and economic loss, there are still no effective treatment options demonstrating an improved outcome in a large multi-center Phase III trial, which can be partially attributed to poor target engagement of delivered therapeutics. Thus, there is a significant unmet need to develop more effective delivery strategies to overcome the biological barriers that would otherwise inhibit transport of materials into the brain to prevent the secondary long-term damage associated with TBI. The complex pathology of TBI involving the blood-brain barrier (BBB) has limited the development of effective therapeutics and diagnostics. Therefore, it is of great importance to develop novel strategies to target the BBB. The leaky BBB caused by a TBI may provide opportunities for therapeutic delivery via nanoparticles (NP). The focus of this review is to provide a survey of NP-based strategies employed in preclinical models of TBI and to provide insights for improved NP based diagnostic or treatment approaches. Both passive and active delivery of various NPs for TBI are discussed. Finally, potential therapeutic targets where improved NP-mediated delivery could increase target engagement are identified with the overall goal of providing insight into open opportunities for NP researchers to begin research in TBI.

Ultrasound-triggered breast tumor sonodynamic therapy through hematoporphyrin monomethyl ether-loaded liposome

Sonodynamic therapy (SDT) which employs ultrasound-triggered sonosensitizers to generate reactive oxygen species (ROS) has been proved to be effective for treatment of cancers. However, it is still desirable for sonosensitizers to be delivered to tumors as effectively as possible. In this study, we prepared the hematoporphyrin monomethyl ether (HMME)-loaded liposome as the sonosensitizers for SDT and evaluated their effects on human MCF-7 breast cancer cells in vitro and in vivo. Liposomes prepared by thin film hydration technique were about 100 nm in size with positive zeta potential and exhibited spherical in shape. Following irradiation of ultrasound which generates intracellular ROS, the liposome facilitated the delivery of HMME to tumor cells. HMME-loaded liposomes showed low cytotoxicity under basal condition but significant sonodynamic effects under ultrasonic irradiation. Notably, HMME-loaded liposomes exhibited spatial distribution of HMME in tumor tissues of mice. The promoted delivery of HMME into the tumors by liposomes was shown by the greater tumor growth inhibition than free HMME after 20-day treatment. Taken together, these results show that HMME-loaded liposome functions as a promising sonosensitizer for SDT, implying the efficient antitumor effects of HMME-based SDT on breast tumor.

Lipidoid-siRNA Nanoparticle-Mediated IL-1β Gene Silencing for Systemic Arthritis Therapy in a Mouse Model

Interleukin-1 beta (IL-1β) plays a central role in the induction of rheumatoid arthritis (RA). In the present study, we demonstrated that lipidoid-polymer hybrid nanoparticle (FS14-NP) can efficiently deliver siRNA against IL-1β (siIL-1β) to macrophages and effectively suppress the pathogenesis of experimental arthritis induced by collagen antibody (CAIA mice). FS14-NP/siIL-1β achieved approximately 70% and 90% gene-silencing efficiency in the RAW 264.7 cell line and intraperitoneal macrophages, respectively. Intravenous administration of FS14-NP/siRNA led to rapid accumulation of siRNA in macrophages within the arthritic joints. Furthermore, FS14-NP/siIL-1β treatment lowered the expression of pro-inflammatory cytokines in arthritic joints and dramatically attenuated ankle swelling, bone erosion, and cartilage destruction. These results demonstrate that FS14-NP/siIL-1β may represent an effective therapy for systemic arthritis and other inflammatory disorders.

Intraperitoneal delivery of acetate-encapsulated liposomal nanoparticles for neuroprotection of the penumbra in a rat model of ischemic stroke

Background

Ischemic stroke is a devastating condition, with metabolic derangement and persistent inflammation enhancing the initial insult of ischaemia. Recombinant tissue plasminogen remains the only effective treatment but limited as therapy must commence soon after the onset of symptoms.

Purpose

We investigated whether acetate, which modulates many pathways including inflammation, may attenuate brain injury in stroke. As acetate has a short blood half-life and high amounts irritate the gastrointestinal tract, acetate was administered encapsulated in a liposomal nanoparticle (liposomal-encapsulated acetate, LITA).

Methods

Transient ischemia was induced by 90 mins middle-cerebral artery occlusion (MCAO) in Sprague-Dawley rats, and LITA or control liposomes given intraperitoneally at occlusion and daily for up to two weeks post-MCAO. Magnetic resonance imaging (MRI) was used to estimate lesion volume at 24 h, 1 and 2 weeks post-MCAO and anterior lateral ventricular volume (ALVv) at 2 weeks post-MCAO. Locomotive behaviour was tested prior to the final MRI scan. After the final scan, brains were collected, and immunohistochemistry was performed.

Results

Lesion volumes were decreased by ~80% from 24 h to one-week post-MCAO, in both control and LITA groups (P⩽0.05). However, the lesion was increased by ~50% over the subsequent 1 to 2 weeks after MCAO in the control group (from 24.1±10.0 to 58.7±28.6 mm³; P⩽0.05) but remained unchanged in the LITA group. ALVv were also attenuated by LITA treatment at 2 weeks post-MCAO (177.2±11.9% and 135.3±10.9% of contralateral ALVv for control and LITA groups, respectively; P⩽0.05). LITA-treated animals also appeared to have improved motor activity, moving with greater average velocity than control animals. Microglial immunoreactivity was ~40% lower in the LITA group compared to the control group (P⩽0.05), but LITA did not modulate neurogenesis, apoptosis, histone acetylation and lipid peroxidation.

Conclusion

LITA appears to attenuate the harmful chronic neuroinflammation observed during brain remodeling after a focal ischemic insult.

Core-Cross-Linked Nanoparticles Reduce Neuroinflammation and Improve Outcome in a Mouse Model of Traumatic Brain Injury

Traumatic brain injury (TBI) is the leading cause of death and disability in children and young adults, yet there are currently no treatments available that prevent the secondary spread of damage beyond the initial insult. The chronic progression of this secondary injury is in part caused by the release of reactive oxygen species (ROS) into surrounding normal brain. Thus, treatments that can enter the brain and reduce the spread of ROS should improve outcome from TBI. Here a highly versatile, reproducible, and scalable method to synthesize core-cross-linked nanoparticles (NPs) from polysorbate 80 (PS80) using a combination of thiol-ene and thiol-Michael chemistry is described. The resultant NPs consist of a ROS-reactive thioether cross-linked core stabilized in aqueous solution by hydroxy-functional oligoethylene oxide segments. These NPs show narrow molecular weight distributions and have a high proportion of thioether units that reduce local levels of ROS. In a controlled cortical impact mouse model of TBI, the NPs are able to rapidly accumulate and be retained in damaged brain as visualized through fluorescence imaging, reduce neuroinflammation and the secondary spread of injury as determined through magnetic resonance imaging and histopathology, and improve functional outcome as determined through behavioral analyses. Our findings provide strong evidence that these NPs may, upon further development and testing, provide a useful strategy to help improve the outcome of patients following a TBI.

Effects of concussion on the blood-brain barrier in humans and rodents

Traumatic brain injury and the long-term consequences of repeated concussions constitute mounting concerns in the United States, with 5.3 million individuals living with a traumatic brain injury-related disability. Attempts to understand mechanisms and possible therapeutic approaches to alleviate the consequences of repeat mild concussions or traumatic brain injury on cerebral vasculature depend on several aspects of the trauma, including: (1) the physical characteristics of trauma or insult that result in damage; (2) the time “window” after trauma in which neuropathological features develop; (3) methods to detect possible breakdown of the blood–brain barrier; and (4) understanding different consequences of a single concussion as compared with multiple concussions. We review the literature to summarize the current understanding of blood–brain barrier and endothelial cell changes post-neurotrauma in concussions and mild traumatic brain injury. Attention is focused on concussion and traumatic brain injury in humans, with a goal of pointing out the gaps in our knowledge and how studies of rodent model systems of concussion may help in filling these gaps. Specifically, we focus on disruptions that concussion causes to the blood–brain barrier and its multifaceted consequences. Importantly, the magnitude of post-concussion blood–brain barrier dysfunction may influence the time course and extent of neuronal recovery; hence, we include in this review comparisons of more severe traumatic brain injury to concussion where appropriate. Finally, we address the important, and still unresolved, issue of how best to detect possible breakdown in the blood–brain barrier following neurotrauma by exploring intravascular tracer injection in animal models to examine leakage into the brain parenchyma.

Molecular imaging of brain localization of liposomes in mice using MALDI mass spectrometry

Phospholipids have excellent biocompatibility and are therefore often used as main components of liposomal drug carriers. In traditional bioanalytics, the in-vivo distribution of liposomal drug carriers is assessed using radiolabeled liposomal constituents. This study presents matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI MSI) as an alternative, label-free method for ex-vivo molecular imaging of liposomal drug carriers in mouse tissue. To this end, indocyanine green as cargo and two liposomal markers, 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol (DPPG) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine conjugated with monodisperse polyethylene glycol (PEG36-DSPE) were incorporated into liposomal carriers and administered to mice. We used MALDI MSI of the two lipid markers in both positive and negative ion mode for visualization of liposome integrity and distribution in mouse organs. Additional MSI of hemoglobin in the same tissue slice and pixel-by-pixel computational analysis of co-occurrence of lipid markers and hemoglobin served as indicator of liposome localization either in parenchyma or in blood vessels. Our proof-of-concept study suggests that liposomal components and indocyanine green distributed into all investigated organs.

Advances in drug delivery to high grade gliomas

If cancer is hard to be treated, brain cancer is even more, caused by the inability of many effective drugs given systemically to cross the blood brain and blood tumor barriers and reach adequate concentrations at the tumor sites. Effective delivery of drugs to brain cancer tissues is thus a necessary, albeit not sufficient, condition to effectively target the disease. In order to analyze the current status of research on drug delivery to high grade gliomas (HGG-WHO grades III and IV), the most frequent and aggressive brain cancers, a literature search was conducted in PubMed using the terms: "drug delivery and brain tumor" over the publication year 2015. Currently explored drug delivery techniques for HGG include the convection and permeabilization-enhanced deliveries, drug-releasing depots and Ommaya reservoirs. The efficacy/safety ratio widely varies among these techniques and the success of current efforts to increase this ratio widely varies as well.

Evaluation of host-guest system to enhance the tamoxifen efficiency

Hydrophobic drugs can absorb as guest molecules inside the cavity of cyclodextrins as host sites. So, forming the drug-cyclodextrin complex can exert a profound effect on the physicochemical and biological properties of the drugs. According to these advantages, in this study, we synthesized the tamoxifen (TMX) loaded cyclodextrin (CD)-conjugated MNPs to evaluate simultaneously the cytotoxicity and sustained release as well as hepatoprotective effect of this nanomedicine. The average size of Fe₃O₄-DPA-PEG-CD-TMX NPs was approximately 31 nm. By energy-dispersive X-ray spectroscopy (EDS), it was revealed that Fe₃O₄ constitutes 14.34% of the composition of modified MNPs. In the other words, nearly 85% of Fe₃O₄-DPA-PEG-CD NPs are made of dopamine (DPA), polyethylene glycol (PEG) and β-cyclodextrin (β-CD). The TMX loaded MNPs (with entrapment efficiency of 33 mg TMX per unit CD (mg) and loading efficiency of 87.5%) showed sustained liberation of TMX molecules (with 91% release in 120 h). Cytotoxicity assay and apoptosis assay by TUNEL analysis revealed that the engineered Fe₃O₄-DPA-PEG-CD-TMX NPs were able to significantly inhibit the MCF-7 breast cancer cells. According to effect of CD on TMX sustained release, it was found that CD can decrease the hepatotoxicity induced by TMX nearly 30%. Based upon these findings, we suggest the Fe₃O₄-DPA-PEG-CD-TMX NPs as an effective multifunctional nanomedicine with simultaneous therapeutic and hepatoprotective effects.

Nano-antioxidants: An emerging strategy for intervention against neurodegenerative conditions

Oxidative stress has for long been linked to the neuronal cell death in many neurodegenerative conditions. Conventional antioxidant therapies have been less effective in preventing neuronal damage caused by oxidative stress due to their inability to cross the blood brain barrier. Nanoparticle antioxidants constitute a new wave of antioxidant therapies for prevention and treatment of diseases involving oxidative stress. It is believed that nanoparticle antioxidants have strong and persistent interactions with biomolecules and would be more effective against free radical induced damage. Nanoantioxidants include inorganic nanoparticles possessing intrinsic antioxidant properties, nanoparticles functionalized with antioxidants or antioxidant enzymes to function as an antioxidant delivery system. Nanoparticles containing antioxidants have shown promise as high-performance therapeutic nanomedicine in attenuating oxidative stress with potential applications in treating and preventing neurodegenerative conditions. However, to realize the full potential of nanoantioxidants, negative aspects associated with the use of nanoparticles need to be overcome to validate their long term applications.