Design of Poly(ethylene Glycol)-Functionalized Hydrophilic Carbon Clusters for Targeted Therapy of Cerebrovascular Dysfunction in Mild Traumatic Brain Injury

Oxidation of Hydrogen Sulfide to Polysulfide and Thiosulfate by a Carbon Nanozyme: Therapeutic Implications with an Emphasis on Down Syndrome

Hydrogen sulfide (H2 S) is a noxious, potentially poisonous, but necessary gas produced from sulfur metabolism in humans. In Down Syndrome (DS), the production of H2 S is elevated and associated with degraded mitochondrial function. Therefore, removing H2 S from the body as a stable oxide could be an approach to reducing the deleterious effects of H2 S in DS. In this report we describe the catalytic oxidation of hydrogen sulfide (H2 S) to polysulfides (HS2+n - ) and thiosulfate (S2 O3 2- ) by poly(ethylene glycol) hydrophilic carbon clusters (PEG-HCCs) and poly(ethylene glycol) oxidized activated charcoal (PEG-OACs), examples of oxidized carbon nanozymes (OCNs). We show that OCNs oxidize H2 S to polysulfides and S2 O3 2- in a dose-dependent manner. The reaction is dependent on O2 and the presence of quinone groups on the OCNs. In DS donor lymphocytes we found that OCNs increased polysulfide production, proliferation, and afforded protection against additional toxic levels of H2 S compared to untreated DS lymphocytes. Finally, in Dp16 and Ts65DN murine models of DS, we found that OCNs restored osteoclast differentiation. This new action suggests potential facile translation into the clinic for conditions involving excess H2 S exemplified by DS.

Oxidized Activated Charcoal Nanozymes: Synthesis, and Optimization for In Vitro and In Vivo Bioactivity for Traumatic Brain Injury

Carbon-based superoxide dismutase (SOD) mimetic nanozymes have recently been employed as promising antioxidant nanotherapeutics due to their distinct properties. The structural features responsible for the efficacy of these nanomaterials as antioxidants are, however, poorly understood. Here, the process-structure-property-performance properties of coconut-derived oxidized activated charcoal (cOAC) nano-SOD mimetics are studied by analyzing how modifications to the nanomaterial's synthesis impact the size, as well as the elemental and electrochemical properties of the particles. These properties are then correlated to the in vitro antioxidant bioactivity of poly(ethylene glycol)-functionalized cOACs (PEG-cOAC). Chemical oxidative treatment methods that afford smaller, more homogeneous cOAC nanoparticles with higher levels of quinone functionalization show enhanced protection against oxidative damage in bEnd.3 murine endothelioma cells. In an in vivo rat model of mild traumatic brain injury (mTBI) and oxidative vascular injury, PEG-cOACs restore cerebral perfusion rapidly to the same extent as the former nanotube-derived PEG-hydrophilic carbon clusters (PEG-HCCs) with a single intravenous injection. These findings provide a deeper understanding of how carbon nanozyme syntheses can be tailored for improved antioxidant bioactivity, and set the stage for translation of medical applications.

Antioxidant Carbon Nanoparticles Inhibit Fibroblast-Like Synoviocyte Invasiveness and Reduce Disease Severity in a Rat Model of Rheumatoid Arthritis

Reactive oxygen species have been involved in the pathogenesis of rheumatoid arthritis (RA). Our goal was to determine the effects of selectively scavenging superoxide (O2•-) and hydroxyl radicals with antioxidant nanoparticles, called poly(ethylene glycol)-functionalized hydrophilic carbon clusters (PEG-HCCs), on the pathogenic functions of fibroblast-like synoviocytes (FLS) from patients with rheumatoid arthritis (RA) and on the progression of an animal model of RA. We used human FLS from patients with RA to determine PEG-HCC internalization and effects on FLS cytotoxicity, invasiveness, proliferation, and production of proteases. We used the pristane-induced arthritis (PIA) rat model of RA to assess the benefits of PEG-HCCs on reducing disease severity. PEG-HCCs were internalized by RA-FLS, reduced their intracellular O2•-, and reduced multiple measures of their pathogenicity in vitro, including proliferation and invasion. In PIA, PEG-HCCs caused a 65% reduction in disease severity, as measured by a standardized scoring system of paw inflammation and caused a significant reduction in bone and tissue damage, and circulating rheumatoid factor. PEG-HCCs did not induce lymphopenia during PIA. Our study demonstrated a role for O2•- and hydroxyl radicals in the pathogenesis of a rat model of RA and showed efficacy of PEG-HCCs in treating a rat model of RA.

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.

Pervasive Genomic Damage in Experimental Intracerebral Hemorrhage: Therapeutic Potential of a Mechanistic-Based Carbon Nanoparticle

Therapy for intracerebral hemorrhage (ICH) remains elusive, in part dependent on the severity of the hemorrhage itself as well as multiple deleterious effects of blood and its breakdown products such as hemin and free iron. While oxidative injury and genomic damage have been seen following ICH, the details of this injury and implications remain unclear. Here, we discovered that, while free iron produced mostly reactive oxygen species (ROS)-related single-strand DNA breaks, hemin unexpectedly induced rapid and persistent nuclear and mitochondrial double-strand breaks (DSBs) in neuronal and endothelial cell genomes and in mouse brains following experimental ICH comparable to that seen with γ radiation and DNA-complexing chemotherapies. Potentially as a result of persistent DSBs and the DNA damage response, hemin also resulted in senescence phenotype in cultured neurons and endothelial cells. Subsequent resistance to ferroptosis reported in other senescent cell types was also observed here in neurons. While antioxidant therapy prevented senescence, cells became sensitized to ferroptosis. To address both senescence and resistance to ferroptosis, we synthesized a modified, catalytic, and rapidly internalized carbon nanomaterial, poly(ethylene glycol)-conjugated hydrophilic carbon clusters (PEG-HCC) by covalently bonding the iron chelator, deferoxamine (DEF). This multifunctional nanoparticle, DEF-HCC-PEG, protected cells from both senescence and ferroptosis and restored nuclear and mitochondrial genome integrity in vitro and in vivo. We thus describe a potential molecular mechanism of hemin/iron-induced toxicity in ICH that involves a rapid induction of DSBs, senescence, and the consequent resistance to ferroptosis and provide a mechanistic-based combinatorial therapeutic strategy.

Use of a bioengineered antioxidant in mouse models of metabolic syndrome

Background: Oxidative stress has been implicated in metabolic syndrome (MetS); however, antioxidants such as vitamin E have had limited success in the clinic. This prompts the question of what effects amore potent antioxidant might produce. A prime candidate is the recently developed bioengineered antioxidant, poly(ethylene glycol)-functionalizedhydrophilic carbon clusters (PEG-HCCs), which are capable of neutralizing the reactive oxygen species (ROS) superoxide anion and hydroxyl radical at10⁶/molecule of PEG-HCC. In this project, we tested the potential of PEG-HCCs as a possible therapeutic for MetS.Results: PEG-HCC treatment lessened lipid peroxidation, aspartate aminotransferase levels, non-fastingblood glucose levels, and JNK phosphorylation inob/ob mice. PEG-HCC-treated WT mice had an increased response to insulin by insulin tolerance tests and adecrease in blood glucose by glucose tolerance tests. These effects were not observed in HFD-fed mice, regardless of treatment. PEG-HCCs were observed in the interstitial space of liver, spleen, skeletal muscle, and adipose tissue. No significant difference was shown in gluconeogenesis or inflammatory gene expression between treatment and dietary groups.Expert Opinion: PEG-HCCs improved some parameters of disease possibly due to a resulting increase in peripheral insulin sensitivity. However, additional studies are needed to elucidate how PEG-HCCsare producing these effects.

Hypertension Exacerbates Cerebrovascular Oxidative Stress Induced by Mild Traumatic Brain Injury: Protective Effects of the Mitochondria-Targeted Antioxidative Peptide SS-31

Traumatic brain injury (TBI) induces cerebrovascular oxidative stress, which is associated with neurovascular uncoupling, autoregulatory dysfunction, and persisting cognitive decline in both pre-clinical models and patients. However, single mild TBI (mTBI), the most frequent form of brain trauma, increases cerebral generation of reactive oxygen species (ROS) only transiently. We hypothesized that comorbid conditions might exacerbate long-term ROS generation in cerebral arteries after mTBI. Because hypertension is the most important cerebrovascular risk factor in populations prone to mild brain trauma, we induced mTBI in normotensive and spontaneously hypertensive rats (SHR) and assessed changes in cytoplasmic and mitochondrial superoxide (O₂-) production by confocal microscopy in isolated middle cerebral arteries (MCA) 2 weeks after mTBI using dihydroethidine (DHE) and the mitochondria-targeted redox-sensitive fluorescent indicator dye MitoSox. We found that mTBI induced a significant increase in long-term cytoplasmic and mitochondrial O₂- production in MCAs of SHRs and increased expression of the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit Nox4, which were reversed to the normal level by treating the animals with the cell-permeable, mitochondria-targeted antioxidant peptide SS-31 (5.7 mg kg^-1 day^-1, i.p.). Persistent mTBI-induced oxidative stress in MCAs of SHRs was significantly decreased by inhibiting vascular NADPH oxidase (apocyinin). We propose that hypertension- and mTBI-induced cerebrovascular oxidative stress likely lead to persistent dysregulation of cerebral blood flow (CBF) and cognitive dysfunction, which might be reversed by SS-31 treatment.

Single Mild Traumatic Brain Injury Induces Persistent Disruption of the Blood-Brain Barrier, Neuroinflammation and Cognitive Decline in Hypertensive Rats

Traumatic brain injury (TBI) induces blood-brain barrier (BBB) disruption, which contributes to secondary injury of brain tissue and development of chronic cognitive decline. However, single mild (m)TBI, the most frequent form of brain trauma disrupts the BBB only transiently. We hypothesized, that co-morbid conditions exacerbate persistent BBB disruption after mTBI leading to long term cognitive dysfunction. Since hypertension is the most important cerebrovascular risk factor in populations prone to mild brain trauma, we induced mTBI in normotensive Wistar and spontaneously hypertensive rats (SHR) and we assessed BBB permeability, extravasation of blood-borne substances, neuroinflammation and cognitive function two weeks after trauma. We found that mTBI induced a significant BBB disruption two weeks after trauma in SHRs but not in normotensive Wistar rats, which was associated with a significant accumulation of fibrin and increased neuronal expression of inflammatory cytokines TNFα, IL-1β and IL-6 in the cortex and hippocampus. SHRs showed impaired learning and memory two weeks after mild TBI, whereas cognitive function of normotensive Wistar rats remained intact. Future studies should establish the mechanisms through which hypertension and mild TBI interact to promote persistent BBB disruption, neuroinflammation and cognitive decline to provide neuroprotection and improve cognitive function in patients with mTBI.

Catalytic oxidation and reduction reactions of hydrophilic carbon clusters with NADH and cytochrome C: features of an electron transport nanozyme

Previously, our group reported on the promising efficacy of poly(ethylene glycol)-hydrophilic carbon clusters (PEG-HCCs) to work as broadly active and high capacity antioxidants in brain ischemia and injury models including stroke and traumatic brain injury coupled with hemorrhagic shock. PEG-HCCs are a carbon nanomaterial derived from harsh oxidation of single wall carbon nanotubes and covalently modified with poly(ethylene glycol). They retain no tubular remnants and are composed of a highly oxidized carbon core functionalized with epoxy, peroxyl, quinone, ketone, carboxylate, and hydroxyl groups. HCCs are the redox active carbon core of PEG-HCCs, which have a broad reduction potential range starting at +200 mV and extending to -2 V. Here we describe a new property of these materials: the ability to catalytically transfer electrons between key surrogates and proteins of the mitochondrial electron transport complex in a catalytic fashion consistent with the concept of a nanozyme. The estimated reduction potential of PEG-HCCs is similar to that of ubiquinone and they enabled the catalytic transfer of electrons from low reduction potential species to higher reduction electron transport complex constituents. PEG-HCCs accelerated the reduction of resazurin (a test indicator of mitochondrial viability) and cytochrome c by NADH and ascorbic acid in solution. Kinetic experiments suggested a transient tertiary complex. Electron paramagnetic resonance demonstrated NADH increased the magnitude of PEG-HCCs' intrinsic radical, which then reduced upon subsequent addition of cytochrome c or resazurin. Deconvolution microscopy identified PEG-HCCs in close proximity to mitochondria after brief incubation with cultured SHSY-5Y human neuroblastoma cells. Compared to methylene blue (MB), considered a prototypical small molecule electron transport shuttle, PEG-HCCs were more protective against toxic effects of hydrogen peroxide in vitro and did not demonstrate impaired cell viability as did MB. PEG-HCCs were protective in vitro when cells were exposed to sodium cyanide, a mitochondrial complex IV poison. Because mitochondria are a major source of free radicals in pathology, we suggest that this newly described nanozyme action helps explain their in vivo efficacy in a range of injury models. These findings may also extend their use to mitochondrial disorders.

Highly Oxidized Graphene Quantum Dots from Coal as Efficient Antioxidants

Graphene quantum dots (GQDs) have recently been employed in various fields including medicine as antioxidants, primarily because of favorable biocompatibility in comparison to common inorganic quantum dots, although the structural features that lead to the biological activities of GQDs are poorly understood. Here, we report that coal-derived GQDs and their poly(ethylene glycol)-functionalized derivatives serve as efficient antioxidants, and we evaluate their electrochemical, chemical, and in vitro biological activities.

Functional and Structural Improvement with a Catalytic Carbon Nano-Antioxidant in Experimental Traumatic Brain Injury Complicated by Hypotension and Resuscitation

Hypotension worsens outcome after all severities of traumatic brain injury (TBI), with loss of cerebral autoregulation being a potential contributor. Previously, we demonstrated that intravenous injection of a high capacity catalytic antioxidant, poly(ethylene)glycol conjugated hydrophilic carbon clusters (PEG-HCCs) rapidly restored cerebral perfusion and acutely restored brain oxidative balance in a TBI model complicated by hemorrhagic hypotension without evidence of toxicity. Here, we tested whether these acute effects translated into behavioral and structural benefit. TBI was generated by a cortical contusion impactor in 38 Long Evans rats, followed by blood withdrawal to a target mean arterial pressure of 40 mm Hg. PEG-HCC (2 mg/kg) or diluent was injected intravenously 80 min later at the onset of blood resuscitation followed by another injection 2 h later (doses determined in prior studies). Performance on beam walking (performed on days 1-5) and Morris water maze (MWM) (performed on days 11-15) was tested, and lesion size was determined at the termination. PEG-HCC treatment nearly completely prevented motor dysfunction (p < 0.001 vs. diluent), improved MWM performance (p < 0.001; treatment vs. time interaction) and reduced lesion size by 61% (p = 0.054). Here we show that treatment with PEG-HCCs at a clinically realistic time point (onset of resuscitation) prevented a major portion of the neurological dysfunction induced in this TBI model, and that PEG-HCCs are candidates for additional study as a potential therapeutic agent.

Inducible lung epithelial resistance requires multisource reactive oxygen species generation to protect against bacterial infections

Pneumonia remains a global health threat, in part due to expanding categories of susceptible individuals and increasing prevalence of antibiotic resistant pathogens. However, therapeutic stimulation of the lungs’ mucosal defenses by inhaled exposure to a synergistic combination of Toll-like receptor (TLR) agonists known as Pam2-ODN promotes mouse survival of pneumonia caused by a wide array of pathogens. This inducible resistance to pneumonia relies on intact lung epithelial TLR signaling, and inducible protection against viral pathogens has recently been shown to require increased production of epithelial reactive oxygen species (ROS) from multiple epithelial ROS generators. To determine whether similar mechanisms contribute to inducible antibacterial responses, the current work investigates the role of ROS in therapeutically-stimulated protection against Pseudomonas aerugnosa challenges. Inhaled Pam2-ODN treatment one day before infection prevented hemorrhagic lung cytotoxicity and mouse death in a manner that correlated with reduction in bacterial burden. The bacterial killing effect of Pam2-ODN was recapitulated in isolated mouse and human lung epithelial cells, and the protection correlated with inducible epithelial generation of ROS. Scavenging or targeted blockade of ROS production from either dual oxidase or mitochondrial sources resulted in near complete loss of Pam2-ODN-induced bacterial killing, whereas deficiency of induced antimicrobial peptides had little effect. These findings support a central role for multisource epithelial ROS in inducible resistance against a bacterial pathogen and provide mechanistic insights into means to protect vulnerable patients against lethal infections.

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes (II)

An updated comprehensive review to help researchers understand nanozymes better and in turn to advance the field.

Inducible Lung Epithelial Resistance Requires Multisource Reactive Oxygen Species Generation To Protect against Viral Infections

Viral pneumonias cause profound worldwide morbidity, necessitating novel strategies to prevent and treat these potentially lethal infections. Stimulation of intrinsic lung defenses via inhalation of synergistically acting Toll-like receptor (TLR) agonists protects mice broadly against pneumonia, including otherwise-lethal viral infections, providing a potential opportunity to mitigate infectious threats. As intact lung epithelial TLR signaling is required for the inducible resistance and as these cells are the principal targets of many respiratory viruses, the capacity of lung epithelial cells to be therapeutically manipulated to function as autonomous antiviral effectors was investigated. Our work revealed that mouse and human lung epithelial cells could be stimulated to generate robust antiviral responses that both reduce viral burden and enhance survival of isolated cells and intact animals. The antiviral protection required concurrent induction of epithelial reactive oxygen species (ROS) from both mitochondrial and dual oxidase sources, although neither type I interferon enrichment nor type I interferon signaling was required for the inducible protection. Taken together, these findings establish the sufficiency of lung epithelial cells to generate therapeutically inducible antiviral responses, reveal novel antiviral roles for ROS, provide mechanistic insights into inducible resistance, and may provide an opportunity to protect patients from viral pneumonia during periods of peak vulnerability.IMPORTANCE Viruses are the most commonly identified causes of pneumonia and inflict unacceptable morbidity, despite currently available therapies. While lung epithelial cells are principal targets of respiratory viruses, they have also been recently shown to contribute importantly to therapeutically inducible antimicrobial responses. This work finds that lung cells can be stimulated to protect themselves against viral challenges, even in the absence of leukocytes, both reducing viral burden and improving survival. Further, it was found that the protection occurs via unexpected induction of reactive oxygen species (ROS) from spatially segregated sources without reliance on type I interferon signaling. Coordinated multisource ROS generation has not previously been described against viruses, nor has ROS generation been reported for epithelial cells against any pathogen. Thus, these findings extend the potential clinical applications for the strategy of inducible resistance to protect vulnerable people against viral infections and also provide new insights into the capacity of lung cells to protect against infections via novel ROS-dependent mechanisms.

Efficacy of Novel Carbon Nanoparticle Antioxidant Therapy in a Severe Model of Reversible Middle Cerebral Artery Stroke in Acutely Hyperglycemic Rats

INTRODUCTION

While oxidative stress can be measured during transient cerebral ischemia, antioxidant therapies for ischemic stroke have been clinically unsuccessful. Many antioxidants are limited in their range and/or capacity for quenching radicals and can generate toxic intermediates overwhelming depleted endogenous protection. We developed a new antioxidant class, 40 nm × 2 nm carbon nanoparticles, hydrophilic carbon clusters, conjugated to poly(ethylene glycol) termed PEG-HCCs. These particles are high-capacity superoxide dismutase mimics, are effective against hydroxyl radical, and restore the balance between nitric oxide and superoxide in the vasculature. Here, we report the effects of PEG-HCCs administered during reperfusion after transient middle cerebral artery occlusion (tMCAO) by suture in the rat under hyperglycemic conditions. Hyperglycemia occurs in one-third of stroke patients and worsens clinical outcome. In animal models, this worsening occurs largely by accelerating elaboration of reactive oxygen species (ROS) during reperfusion.

METHODS

PEG-HCCs were studied for their protective ability against hydrogen peroxide in b.End3 brain endothelial cell line and E17 primary cortical neuron cultures. In vivo, hyperglycemia was induced by streptozotocin injection 2 days before tMCAO. 58 Male Sprague-Dawley rats were analyzed. They were injected IV with PBS or PEG-HCCs (4 mg/kg 2×) at the time of recanalization after either 90- or 120-min occlusion. Rats were survived for up to 3 days, and infarct volume characteristics and neurological functional outcome (modified Bederson Score) were assessed.

RESULTS

PEG-HCCs were protective against hydrogen peroxide in both culture models. In vivo improvement was found after PEG-HCCs with 90-min ischemia with reduction in infarct size (42%), hemisphere swelling (46%), hemorrhage score (53%), and improvement in Bederson score (70%) (p = 0.068-0.001). Early high mortality in the 2-h in the PBS control group precluded detailed analysis, but a trend was found in improvement in all factors, e.g., reduction in infarct volume (48%; p = 0.034) and a 56% improvement in Bederson score (p = 0.055) with PEG-HCCs.

CONCLUSION

This nano-antioxidant showed some improvement in several outcome measures in a severe model of tMCAO when administered at a clinically relevant time point. Long-term studies and additional models are required to assess potential for clinical use, especially for patients hyperglycemic at the time of their stroke, as these patients have the worst outcomes.

Physical and electrical characterization of TexasPEG: An electrically conductive neuronal scaffold

BACKGROUND

Graphene and its derivatives have been shown to be biocompatible and electrically active materials upon which neurons readily grow. The fusogen poly(ethylene glycol) (PEG) has been shown to improve outcomes after cervical and dorsal spinal cord transection. The long and narrow PEGylated graphene nanoribbon stacks (PEG-GNRs) with their 5 μm × 200 nm × 10 nm dimensions can provide a scaffold upon which neurons can grow and fuse. We disclose here the extensive characterization data for the PEG-GNRs.

METHODS

PEG-GNRs were chemically synthesized and chemically and electrically characterized.

RESULTS

The average aspect ratio of the PEG-GNRs was determined to be ~85, which corresponds to a critical percolation value (the point where insulating material becomes conductive by addition of conductive particles) of 1%. However, there was not a sharp increase in AC conductivity at frequencies relevant to action potentials.

CONCLUSION

A robust characterization of PEG-GNRs is discussed, though the precise origin of efficacy in improving outcomes following spinal cord transection is not known.

Traumatic brain injury-induced autoregulatory dysfunction and spreading depression-related neurovascular uncoupling: Pathomechanisms, perspectives, and therapeutic implications

Traumatic brain injury (TBI) is a major health problem worldwide. In addition to its high mortality (35-40%), survivors are left with cognitive, behavioral, and communicative disabilities. While little can be done to reverse initial primary brain damage caused by trauma, the secondary injury of cerebral tissue due to cerebromicrovascular alterations and dysregulation of cerebral blood flow (CBF) is potentially preventable. This review focuses on functional, cellular, and molecular changes of autoregulatory function of CBF (with special focus on cerebrovascular myogenic response) that occur in cerebral circulation after TBI and explores the links between autoregulatory dysfunction, impaired myogenic response, microvascular impairment, and the development of secondary brain damage. We further provide a synthesized translational view of molecular and cellular mechanisms involved in cortical spreading depolarization-related neurovascular dysfunction, which could be targeted for the prevention or amelioration of TBI-induced secondary brain damage.

Preferential uptake of antioxidant carbon nanoparticles by T lymphocytes for immunomodulation

Autoimmune diseases mediated by a type of white blood cell-T lymphocytes-are currently treated using mainly broad-spectrum immunosuppressants that can lead to adverse side effects. Antioxidants represent an alternative approach for therapy of autoimmune disorders; however, dietary antioxidants are insufficient to play this role. Antioxidant carbon nanoparticles scavenge reactive oxygen species (ROS) with higher efficacy than dietary and endogenous antioxidants. Furthermore, the affinity of carbon nanoparticles for specific cell types represents an emerging tactic for cell-targeted therapy. Here, we report that nontoxic poly(ethylene glycol)-functionalized hydrophilic carbon clusters (PEG-HCCs), known scavengers of the ROS superoxide (O2•-) and hydroxyl radical, are preferentially internalized by T lymphocytes over other splenic immune cells. We use this selectivity to inhibit T cell activation without affecting major functions of macrophages, antigen-presenting cells that are crucial for T cell activation. We also demonstrate the in vivo effectiveness of PEG-HCCs in reducing T lymphocyte-mediated inflammation in delayed-type hypersensitivity and in experimental autoimmune encephalomyelitis, an animal model of multiple sclerosis. Our results suggest the preferential targeting of PEG-HCCs to T lymphocytes as a novel approach for T lymphocyte immunomodulation in autoimmune diseases without affecting other immune cells.

What's New in Traumatic Brain Injury: Update on Tracking, Monitoring and Treatment

Traumatic brain injury (TBI), defined as an alteration in brain functions caused by an external force, is responsible for high morbidity and mortality around the world. It is important to identify and treat TBI victims as early as possible. Tracking and monitoring TBI with neuroimaging technologies, including functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI), positron emission tomography (PET), and high definition fiber tracking (HDFT) show increasing sensitivity and specificity. Classical electrophysiological monitoring, together with newly established brain-on-chip, cerebral microdialysis techniques, both benefit TBI. First generation molecular biomarkers, based on genomic and proteomic changes following TBI, have proven effective and economical. It is conceivable that TBI-specific biomarkers will be developed with the combination of systems biology and bioinformation strategies. Advances in treatment of TBI include stem cell-based and nanotechnology-based therapy, physical and pharmaceutical interventions and also new use in TBI for approved drugs which all present favorable promise in preventing and reversing TBI.

Highly efficient conversion of superoxide to oxygen using hydrophilic carbon clusters

Many diseases are associated with oxidative stress, which occurs when the production of reactive oxygen species (ROS) overwhelms the scavenging ability of an organism. Here, we evaluated the carbon nanoparticle antioxidant properties of poly(ethylene glycolated) hydrophilic carbon clusters (PEG-HCCs) by electron paramagnetic resonance (EPR) spectroscopy, oxygen electrode, and spectrophotometric assays. These carbon nanoparticles have 1 equivalent of stable radical and showed superoxide (O2 (•-)) dismutase-like properties yet were inert to nitric oxide (NO(•)) as well as peroxynitrite (ONOO(-)). Thus, PEG-HCCs can act as selective antioxidants that do not require regeneration by enzymes. Our steady-state kinetic assay using KO2 and direct freeze-trap EPR to follow its decay removed the rate-limiting substrate provision, thus enabling determination of the remarkable intrinsic turnover numbers of O2 (•-) to O2 by PEG-HCCs at >20,000 s(-1). The major products of this catalytic turnover are O2 and H2O2, making the PEG-HCCs a biomimetic superoxide dismutase.

Hydrophilic carbon clusters as therapeutic, high-capacity antioxidants

Oxidative stress reflects an excessive accumulation of reactive oxygen species (ROS) and is a hallmark of several acute and chronic human pathologies. Although many antioxidants have been investigated, most have demonstrated poor efficacy in clinical trials. Here we discuss the limitations of current antioxidants and describe a new class of nanoparticle antioxidants, poly(ethylene glycol)-functionalized hydrophilic carbon clusters (PEG-HCCs). PEG-HCCs show high capacity to annihilate ROS such as superoxide (O2(•-)) and the hydroxyl (HO(•)) radical, show no reactivity toward the nitric oxide radical (NO(•)), and can be functionalized with targeting moieties without loss of activity. Given these properties, we propose that PEG-HCCs offer an exciting new area of study for the treatment of numerous ROS-induced human pathologies.

Reducing X-Ray Induced Oxidative Damages in Fibroblasts with Graphene Oxide

A major issue of X-ray radiation therapy is that normal cells can be damaged, limiting the amount of X-rays that can be safely delivered to a tumor. This paper describes a new method based on graphene oxide (GO) to protect normal cells from oxidative damage by removing free radicals generated by X-ray radiation using grapheme oxide (GO). A variety of techniques such as cytotoxicity, genotoxicity, oxidative assay, apoptosis, γ-H2AX expression, and micro-nucleus assay have been used to assess the protective effect of GO in cultured fibroblast cells. It is found that although GO at higher concentration (100 and 500 μg/mL) can cause cell death and DNA damage, it can effectively remove oxygen free radicals at a lower concentration of 10 μg/mL. The level of DNA damage and cell death is reduced by 48%, and 39%, respectively. Thus, low concentration GO can be used as an effective radio-protective agent in occupational and therapeutic settings.

Green polymer chemistry VIII: synthesis of halo-ester-functionalized poly(ethylene glycol)s via enzymatic catalysis

Halo-ester-functionalized poly(ethylene glycol)s (PEGs) are successfully prepared by the transesterification of alkyl halo-esters with PEGs using Candida antarctica lipase B (CALB) as a biocatalyst under the solventless conditions. Transesterifications of chlorine, bromine, and iodine esters with tetraethylene glycol monobenzyl ether (BzTEG) are quantitative in less than 2.5 h. The transesterification of halo-esters with PEGs are complete in 4 h. (1) H and (13) C NMR spectroscopy with MALDI-ToF and ESI mass spectrometry confirm the structure and purity of the products. This method provides a convenient and "green" process to effectively produce halo-ester PEGs.