Carbogenic Nanozyme with Ultrahigh Reactive Nitrogen Species Selectivity for Traumatic Brain Injury

In situ forming and biocompatible hyaluronic acid hydrogel with reactive oxygen species-scavenging activity to improve traumatic brain injury repair by suppressing oxidative stress and neuroinflammation

The efficacy of neural repair and regeneration strategies for traumatic brain injury (TBI) treatment is greatly hampered by the harsh brain lesion microenvironment including oxidative stress and hyper-inflammatory response. Functionalized hydrogel with the capability of oxidative stress suppression and neuroinflammation inhibition will greatly contribute to the repairment of TBI. Herein, antioxidant gallic acid-grafted hyaluronic acid (HGA) was combined with hyaluronic acid-tyramine (HT) polymer to develop an injectable hydrogel by dual-enzymatically crosslinking method. The resulting HT/HGA hydrogel is biocompatible and possesses effective scavenging activity against DPPH and hydroxyl radicals. Meanwhile, this hydrogel improved cell viability and reduced intracellular reactive oxygen species (ROS) production under H₂O₂ insult. The in vivo study showed that in situ injection of HT/HGA hydrogel significantly reduced malondialdehyde (MDA) production and increased glutathione (GSH) expression in lesion area after treatment for 3 or 21 days, which might be associated with the activation of Nrf2/HO-1 pathway. Furthermore, this hydrogel promoted the microglia polarization to M2 (Arg1) phenotype, it also decreased the level of proinflammatory factors including TNF-α and IL-6 and increased anti-inflammatory factor expression of IL-4. Finally, blood-brain barrier (BBB) was protected, neurogenesis in hippocampus was promoted, and the motor, learning and memory ability was enhanced. Therefore, this injectable, biocompatible, and antioxidant hydrogel exhibits a huge potential for treating TBI and allows us to recognize the great value of this novel biomaterial for remodeling brain structure and function.

Biochar Nanozyme from Silkworm Excrement for Scavenging Vapor-Phase Free Radicals in Cigarette Smoke

Serious lung diseases and other health problems caused by tobacco consumption are becoming more and more prominent all over the world. Scavenging the excessive harmful free radicals in cigarette smoke is proven to be an effective method in reducing the above problems. Carbon-based nanozymes have been widely studied due to their ability of scavenging free radicals. Accordingly, the biochar derived from silkworm excrement was reported as a nanozyme with free radical scavenging ability. The biochar nanozyme calcination at 900 °C with better free radical scavenging abilities was loaded into commercial cigarette filters for the following free radical scavenging verification in tobacco smoke. Mouse model results reveal the lung tissue could be improved by the addition of biochar nanozyme. This work not only provides an effective approach to reduce the harm caused by tobacco but also provides potential applications to rationally realize low-cost, ease of production, and a wide variety of biochar sources.

Ti3C2 nanosheets with broad-spectrum antioxidant activity for cytoprotection against oxidative stress

Redox regulation in biological systems represents a fascinating method for treatment and prevention of oxidative stress induced diseases. The key and difficult point is to find ideal materials with excellent antioxidant capability and good biocompatibility. To this end, ultra-thin two-dimensional MXene (Ti3C2) nanosheets (NSs) were investigated for their antioxidant capability. It is found that Ti3C2 NSs can scavenge efficiently reactive oxygen and nitrogen species (˙OH, H2O2, and ˙NO), ABTS+˙ and DPPH˙ free radicals in a concentration dependent manner, showing broad-spectrum antioxidant activities. Ti3C2 NSs exhibit higher antioxidant activity and broader antioxidant capability than natural antioxidant molecules. The significant role of PEG modified Ti3C2 with good stability in preventing cell damage against oxidative stress was demonstrated. Upon treatment of H2O2 induced oxidative stress with Ti3C2, the intracellular ROS level decreases and the cell survival rate increases significantly. An antioxidant mechanism based on gradient oxidation was proposed to account for the superior antioxidant activity of Ti3C2. Our result proves that ultra-thin MXenes as antioxidants have great potential in preventing oxidative stress caused biological damage.

Prussian Blue Nanozyme as a Pyroptosis Inhibitor Alleviates Neurodegeneration

Current pharmacological interventions for Parkinson's disease (PD) remain unsatisfactory in clinical settings. Inflammasome-mediated pyroptosis represents a potential therapeutic target for the alleviation of neurodegenerative diseases. The development of inflammasome-mediated pyroptosis agonists or antagonists may transform the treatment of neurodegenerative diseases. However, the identification of specific compounds that inhibit pyroptosis remains challenging. Herein, Prussian blue nanozyme (PBzyme) is revealed as a pyroptosis inhibitor to alleviate the neurodegeneration in mouse and cell models of PD. PBzyme protects the microglia and neurons against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). PBzyme alleviates motor deficits, attenuates the damage of mitochondrial membrane potential, and rescues dopaminergic neurons. Furthermore, intra-cerebroventricular injection of PBzyme reduces dopaminergic degeneration and inhibits neuroinflammation in an MPTP-induced PD mouse model. Both in vitro and in vivo results demonstrate that PBzyme reduces the activation of microglial nucleotide-binding domain and leucine-rich repeat family pyrin domain containing 3 (NLRP3) inflammasomes and caspase-1 by scavenging reactive oxygen species, thereby downregulating gasdermin D (GSDMD) cleavage as well as inflammatory factor production, and eventually leading to the inhibition of microglia pyroptosis. Overall, this work highlights the neuroprotective effects of PBzyme as a pyroptosis inhibitor and provides valuable mechanistic insights and a potential therapeutic strategy for the treatment of PD.

Rescuing ischemic stroke by biomimetic nanovesicles through accelerated thrombolysis and sequential ischemia-reperfusion protection

Rational design of nanomedicine to accelerate thrombolysis and sequentially avoid thrombolysis-mediated reperfusion injury is still a challenge. Here, we develop a biomimetic nanovesicle (tPA/MNP@PM, tMP) by simple encapsulating melanin nanoparticles (MNP) and tPA with a platelet membrane vesicle (PM), which integrates the thrombus targeting property of PM, the photothermal conversion performance and free radical scavenging property of natural melanin for cascaded ischemic stroke treatment. Benefiting from natural thrombus-targeted adhesion capability of PM, nanovesicles could efficiently target thrombus site. Then near-infrared (NIR) mediated photothermal of MNP could lead to rupture of nanovesicles, thus achieving precise release of tPA in thrombus. Interestingly, local hyperthermia also increases the activity of tPA for accelerating thrombolysis. Afterwards, site specific released MNP (4.5 nm) accompanied by hemoperfusion can cross the BBB and accumulate in cerebral ischemia site, scavenging various free radicals and suppressing inflammation- and immune response-induced injury to achieve neuroprotection after thrombolysis. In addition, the biomimetic nanovesicle could block tPA-induced brain hemorrhage after stroke to improve thrombolytic therapy. The evaluation in ischemic stroke mice confirmed that the simple-prepared nanomedicine with cascaded thrombus targeting, precise thrombolysis and ischemia-reperfusion protection properties can significantly enhance the treatment effect of ischemic stroke. STATEMENT OF SIGNIFICANCE: Ischemic stroke is recognized as a leading cause of death and disability in the world. Rational design of nanomedicine to accelerate thrombolysis and sequentially avoid thrombolysis-mediated reperfusion injury is still a challenge. Herein, a biomimetic nanovesicle (tMP) was developed for sequential ischemic stroke treatment. It could overcome the drawbacks of free tPA for safe thrombolysis: i) platelet membrane biomimetic coating significantly increases thrombus targeting; ii) NIR-mediated photothermal of natural melanin precise controlled release of tPA in thrombus in situ, and local hyperthermia also increases the thrombolytic activity of tPA. Notably, released melanin nanoparticles (4.5 nm) accompanied by hemoperfusion can across BBB and avoid ischemia-reperfusion injury through free radical scavenging and inflammation/immune response suppression.

Electrochemical Microfluidic Multiplexed Bioanalysis by a Highly Active Bottlebrush-like Nanocarbon Microelectrode

We present a highly efficient multichannel microfluidic electrochemical sensor integrated with an electroactive nanocarbon microelectrode for sensitive and selective detection of multiple biomarkers in different biological samples. Our results have shown that ionic liquid-assisted wet spinning followed by tailored growth of metal-organic frameworks and pyrolysis treatment led to structural and molecular engineering of mechanically robust all-carbon microfibers for excellent electrochemical activities. The flexible bottlebrush-like nanocarbon microelectrode features a "stem" of freestanding N, B-codoped graphene fiber and high-density "bristles" of Co, N-codoped carbon nanotube arrays, leading to promoted electrocatalytic mechanism that has been substantiated by density functional theory calculations. The structural characteristics, high catalytic activities, and favorable biocompatibility of the bottlebrush nanocarbon electrodes provide opportunities for multichannel, microfluidic detection of redox-active biomolecules, including hydrogen sulfide (H₂S), dopamine (DA), uric acid (UA), and ascorbic acid (AA), and have been applied to on-chip monitoring of H₂S and DA released from live cancer cells or neuroblastoma cells and DA, UA, and AA in trace amounts of body fluids such as sweat, finger blood, tears, saliva, and urine, which is of great significance for clinical diagnosis and prognosis in point-of-care testing.

Graphene and graphene-related materials as brain electrodes

Neural electrodes are used for acquiring neuron signals in brain-machine interfaces, and they are crucial for next-generation neuron engineering and related medical applications. Thus, developing flexible, stable and high-resolution neural electrodes will play an important role in stimulation, acquisition, recording and analysis of signals. Compared with traditional metallic electrodes, electrodes based on graphene and other two-dimensional materials have attracted wide attention in electrophysiological recording and stimulation due to their excellent physical properties such as unique flexibility, low resistance, and high optical transparency. In this review, we have reviewed the recent progress of electrodes based on graphene, graphene/polymer compounds and graphene-related materials for neuron signal recording, stimulation, and related optical signal coupling technology, which provides an outlook on the role of electrodes in the nanotechnology-neuron interface as well as medical diagnosis.

An oligomeric semiconducting nanozyme with ultrafast electron transfers alleviates acute brain injury

Artificial enzymes have attracted wide interest in disease diagnosis and biotechnology due to high stability, easy synthesis, and cost effectiveness. Unfortunately, their catalytic rate is limited to surface electron transfer, affecting the catalytic and biological activity. Here, we report an oligomeric nanozyme (O-NZ) with ultrafast electron transfer, achieving ultrahigh catalytic activity. O-NZ shows electron transfer of 1.8 nanoseconds in internal cores and 1.2 picoseconds between core and ligand molecule, leading to ultrahigh superoxidase dismutase–like and glutathione peroxidase–like activity (comparable with natural enzyme, Michaelis constant = 0.87 millimolars). Excitingly, O-NZ can improve the 1-month survival rate of mice with acute brain trauma from 50 to 90% and promote the recovery of long-term neurocognition. Biochemical experiments show that O-NZ can decrease harmful peroxide and superoxide via in vivo catalytic chain reaction and reduce acute neuroinflammation via nuclear factor erythroid-2 related factor 2–mediated up-regulation of heme oxygenase-1 expression.

Nanozymes Regulate Redox Homeostasis in ROS-Related Inflammation

Reactive oxygen species (ROS), in moderate amounts, play an essential role in regulating different physiological functions in organisms. However, increased amounts of ROS may cause oxidative stress and damage to biomolecules, leading to a variety of diseases including inflammation and even cancer. Therefore, ROS scavenging reagents are needed to maintain healthy levels of ROS. With considerable advances in nanotechnology, nanozymes possess SOD or CAT-like activities with outstanding free radical scavenging activity, facile synthesis conditions, and excellent biocompatibility. Based on these extraordinary properties, nanozymes has been used to modulate the redox homeostasis and relieve the ROS-related injury. This has led to the emergence of nanozyme-based therapies. In the current review, we presented recently developed applications of nanozymes to treat ROS-dependent disorders with an emphasis on inflammatory and brain diseases.

Catalytically active gold clusters with atomic precision for noninvasive early intervention of neurotrauma

Background

Neurotrauma is a worldwide public health problem which can be divided into primary and secondary damge. The primary damge is caused by external forces and triggers the overproduction of peroxides and superoxides, leading to long-lasting secondary damage including oxidative stress, wound infection and immunological reactions. The emerging catalysts have shown great potential in the treatment of brain injury and neurogenic inflammation, but are limited to biosafety issues and delivery efficiency.

Results

Herein, we proposed the noninvasive delivery route to brain trauma by employing highly active gold clusters with enzyme-like activity to achieve the early intervention. The decomposition rate to H₂O₂ of the ultrasmall gold clusters is 10 times that of glassy carbon (GC) electrodes, indicating excellent catalytic activity. The gold clusters can relieve the oxidative stress and decrease the excessive O₂^·− and H₂O₂ both in vitro and in vivo. Besides, gold clusters can accelerate the wound healing of brain trauma and alleviate inflammation via inhibiting the activation of astrocytes and microglia through noninvasive adminstration. decrease the peroxide and superoxide of brain tissue.

Conclusions

Present work shows noninvasive treatment is a promising route for early intervention of brain trauma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01071-4.

A Co-Doped Fe3O4 Nanozyme Shows Enhanced Reactive Oxygen and Nitrogen Species Scavenging Activity and Ameliorates the Deleterious Effects of Ischemic Stroke

Acute ischemic stroke has become the major cause of mortality and disability worldwide. Following ischemic stroke, the reperfusion injury is mainly mediated by the burst of reactive oxygen and nitrogen species (RONS). Therefore, blocking the excessive production or removing RONS holds great promise as a potential therapeutic strategy. Herein, we developed a Co-doped Fe3O4 nanozyme that is capable of scavenging H2O2, O2•-, •NO, and ONOO- in vitro and in vivo and provides neuroprotection against ischemic stroke. In vitro experiments showed that pre-incubation with the Co-Fe3O4 nanozyme could prevent neurotoxicity and neuroinflammation induced by H2O2 or lipopolysaccharide, respectively, in HT22 cells. After intravenous administration, the Co-Fe3O4 nanozyme showed no signs of toxicity in peripheral organs of C57BL/6J mice, even after prolonged delivery for 4 weeks. In permanent photothrombotic stroke model and transient middle cerebral artery occlusion stroke model, the Co-Fe3O4 nanozyme specifically accumulated in the infarct rim at 72 h post-stroke and was endocytosed by neurons, astrocytes, microglia, and endothelial cells. Importantly, the Co-Fe3O4 nanozyme delivery reduced the infarct volume in both stroke models. The observation that the Co-Fe3O4 nanozyme was efficacious in two well-characterized ischemic stroke models provides strong evidence that it represents a powerful tool for targeting oxidative and nitrosative stress in the ischemic brain.

Microfluidic encapsulated manganese organic frameworks as enzyme mimetics for inflammatory bowel disease treatment

Metal organic frameworks (MOFs) with physicochemical properties and adjustable structures have been proposed as very attractive materials. The studies on development of such functional materials tended to fabricate featured MOF objects with fascinating catalytic capabilities to utilize their biomedical values. In this paper, we present novel biocompatible manganese metal organic framework (Mn-MOF)-based catalase mimetics with microfluidic microcapsule encapsulation for intravital inflammatory bowel disease (IBD) treatment. Phosphoserine, a component of the cell membrane, served as an organic ligand to ensure biocompatibility of Mn-MOF. Owing to the core-shell structure of the microcapsule, the Mn-MOF exhibited a well-organized distribution and controlled release features, which could protect them from gastric juice and provide function in the intestine. Upon reaching the sites of the inflammatory bowel, Mn-MOF could effectively scavenge reactive oxygen species (ROS) over-produced by neutrophils and macrophages under various gastrointestinal pH environments, protecting intestinal epithelial cells from ROS damage. The Mn-MOF-encapsulated microcapsules exhibited high performances in treating spontaneous IBD in interleukin-10-deficient mice by relieving the oxidative stress, reducing the inflammation, and restoring the intestinal barrier. These results indicate that the functional Mn-MOF-encapsulated microcapsules have practical applications in the treatment of ROS-associated diseases.

Nanoparticles-mediated emerging approaches for effective treatment of ischemic stroke

Ischemic stroke leads to high disability and mortality. The limited delivery efficiency of most therapeutic substances is a major challenge for effective treatment of ischemic stroke. Inspired by the prominent merit of nanoscale particles in brain targeting and blood-brain barrier (BBB) penetration, various functional nanoparticles have been designed as promising drug delivery platforms that are expected to improve the therapeutic effect of ischemic stroke. Based on the complex pathological mechanisms of ischemic stroke, this review outline and summarize the rationally designed nanoparticles-mediated emerging approaches for effective treatment of ischemic stroke, including recanalization therapy, neuroprotection therapy, and combination therapy. On this bases, the potentials and challenges of nanoparticles in the treatment of ischemic stroke are revealed, and new thoughts and perspectives are proposed for the design of feasible nanoparticles for effective treatment of ischemic stroke.

Prussian blue-based theranostics for ameliorating acute kidney injury

Background

Acute kidney injury (AKI) with high mortality rates is associated with an excess of reactive oxygen/nitrogen species (RONS) within kidney tissues. Recently, nanomedicine antioxidant therapy has been used to alleviate AKI. Herein, we synthesized ultrasmall Prussian blue nanozymes (PB NZs, 4.5 nm) as theranostic agents for magnetic resonance (MR)/photoacoustic (PA) dual-modal imaging guided AKI treatment.

Results

PB NZs exhibited multi-enzyme mimetic abilities, promoting the effective elimination of RONS both in vitro and in vivo. Moreover, benefiting from their imaging contrast properties, the rapid renal accumulation of PB NZs was verified by in vivo PA/MR dual-modal imaging. Due to their excellent enrichment in the kidney and unique multi-enzyme mimetic abilities, ultrasmall PB NZs displayed superior AKI treatment efficacy compared with that of amifostine in two clinically relevant types of AKI induced murine models (either by rhabdomyolysis or cisplatin).

Conclusion

Our findings suggested ultrasmall PB NZs, as nanozyme theranostics, have great potential for AKI management.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01006-z.

A Review on Metal- and Metal Oxide-Based Nanozymes: Properties, Mechanisms, and Applications

Since the ferromagnetic (Fe3O4) nanoparticles were firstly reported to exert enzyme-like activity in 2007, extensive research progress in nanozymes has been made with deep investigation of diverse nanozymes and rapid development of related nanotechnologies. As promising alternatives for natural enzymes, nanozymes have broadened the way toward clinical medicine, food safety, environmental monitoring, and chemical production. The past decade has witnessed the rapid development of metal- and metal oxide-based nanozymes owing to their remarkable physicochemical properties in parallel with low cost, high stability, and easy storage. It is widely known that the deep study of catalytic activities and mechanism sheds significant influence on the applications of nanozymes. This review digs into the characteristics and intrinsic properties of metal- and metal oxide-based nanozymes, especially emphasizing their catalytic mechanism and recent applications in biological analysis, relieving inflammation, antibacterial, and cancer therapy. We also conclude the present challenges and provide insights into the future research of nanozymes constituted of metal and metal oxide nanomaterials.

Inorganic nanomaterials with rapid clearance for biomedical applications

Inorganic nanomaterials that have inherently exceptional physicochemical properties (e.g., catalytic, optical, thermal, electrical, or magnetic performance) that can provide desirable functionality (e.g., drug delivery, diagnostics, imaging, or therapy) have considerable potential for application in the field of biomedicine. However, toxicity can be caused by the long-term, non-specific accumulation of these inorganic nanomaterials in healthy tissues, preventing their large-scale clinical utilization. Over the past several decades, the emergence of biodegradable and clearable inorganic nanomaterials has offered the potential to prevent such long-term toxicity. In addition, a comprehensive understanding of the design of such nanomaterials and their metabolic pathways within the body is essential for enabling the expansion of theranostic applications for various diseases and advancing clinical trials. Thus, it is of critical importance to develop biodegradable and clearable inorganic nanomaterials for biomedical applications. This review systematically summarizes the recent progress of biodegradable and clearable inorganic nanomaterials, particularly for application in cancer theranostics and other disease therapies. The future prospects and opportunities in this rapidly growing biomedical field are also discussed. We believe that this timely and comprehensive review will stimulate and guide additional in-depth studies in the area of inorganic nanomedicine, as rapid in vivo clearance and degradation is likely to be a prerequisite for the future clinical translation of inorganic nanomaterials with unique properties and functionality.

Preclinical studies conducted on nanozyme antioxidants: shortcomings and challenges based on US FDA regulations

The wide prevalence of oxidative stress-induced diseases has led to a growing demand for antioxidant therapeutics worldwide. Nanozyme antioxidants are drawing enormous attention as practical alternatives for conventional antioxidants. The considerable body of research over the last decade and the promising results achieved signify the potential of nanozyme antioxidants to secure a place in the expanding market of antioxidant therapeutics. Nonetheless, there is no report on clinical trials for their further evaluation. Through analyzing in-depth selected papers which have conducted in vivo studies on nanozyme antioxidants, this review aims to pinpoint and discuss possible reasons impeding development of research toward clinical studies and to offer some practical solutions for future studies to bridge the gap between preclinical and clinical stages.

Decoding the Complex Free Radical Cascade by Using a DNA Framework-Based Artificial DNA Encoder

DNA-based molecular communications (DMC) are critical for regulating biological networks to maintain stable organismic functions. However, the complicated, time-consuming information transmission process involved in genome-coded DMC and the limited, vulnerable decoding activity generally lead to communication impairment or failure, in response to external stimuli. Herein, we present a conceptually innovative DMC strategy mediated by the DNA framework-based artificial DNA encoder. With the free-radical cascade as a proof-of-concept study, the artificial DNA encoder shows active sensing and real-time actuation, in situ and broad free radical-decoding efficacy, as well as robust resistance to environmental noise. It can also block undesirable short-to-medium-range communications between free radicals and inflammatory networks, leading to a synergistic anti-obesity effect. The artificial DNA encoder-based DMC may be generalized to other communication systems for a variety of applications.

Chemical design of nanozymes for biomedical applications

With the advancement of nanochemistry, artificial nanozymes with high catalytic stability, low manufacturing and storage cost, and greater design flexibility over natural enzymes, have emerged as a next-generation nanomedicine. The catalytic activity and selectivity of nanozymes can be readily controlled and optimized by the rational chemical design of nanomaterials. This review summarizes the various chemical approaches to regulate the catalytic activity and selectivity of nanozymes for biomedical applications. We focus on the in-depth correlation between the physicochemical characteristics and catalytic activities of nanozymes from several aspects, including regulating chemical composition, controlling morphology, altering the size, surface modification and self-assembly. Furthermore, the chemically designed nanozymes for various biomedical applications such as biosensing, infectious disease therapy, cancer therapy, neurodegenerative disease therapy and injury therapy, are briefly summarized. Finally, the current challenges and future perspectives of nanozymes are discussed from a chemistry point of view. STATEMENT OF SIGNIFICANCE: As a kind of nanomaterials that performs enzyme-like properties, nanozymes perform high catalytic stability, low manufacturing and storage cost, attracting the attention of researchers from various fields. Notably, chemically designed nanozymes with robust catalytic activity, tunable specificity and multi-functionalities are promising for biomedical applications. It's crucial to define the correlation between the physicochemical characteristics and catalytic activities of nanozymes. To help readers understand this rapidly expanding field, in this review, we summarize various chemical approaches that regulate the catalytic activity and selectivity of nanozymes together with the discussion of related mechanisms, followed by the introduction of diverse biomedical applications using these chemically well-designed nanozymes. Hopefully our review will bridge the chemical design and biomedical applications of nanozymes, supporting the extensive research on high-performance nanozymes.

Smart Layer-by-Layer Polymeric Microreactors: pH-Triggered Drug Release and Attenuation of Cellular Oxidative Stress as Prospective Combination Therapy

Polymer capsules fabricated via the layer-by-layer (LbL) approach have emerged as promising biomedical systems for the release of a wide variety of therapeutic agents, owing to their tunable and controllable structure and the possibility to include several functionalities in the polymeric membrane during the fabrication process. However, the limitation of the capsules with a single functionality to overcome the challenges involved in the treatment of complex pathologies denotes the need to develop multifunctional capsules capable of targeting several mediators and/or mechanisms. Oxidative stress is caused by the accumulation of reactive oxygen species [e.g., hydrogen peroxide (H2O2), hydroxyl radicals (•OH), and superoxide anion radicals (•O2-)] in the cellular microenvironment and is a key modulator in the pathology of a broad range of inflammatory diseases. The disease microenvironment is also characterized by the presence of proinflammatory cytokines, increased levels of matrix metalloproteinases, and acidic pH, all of which could be exploited to trigger the release of therapeutic agents. In the present work, multifunctional capsules were fabricated via the LbL approach. Capsules were loaded with an antioxidant enzyme (catalase) and functionalized with a model drug (doxorubicin), which was conjugated to an amine-containing dendritic polyglycerol through a pH-responsive linker. These capsules efficiently scavenge H2O2 from solution, protecting cells from oxidative stress, and release the model drug in acidic microenvironments. Accordingly, in this work, a polymeric microplatform is presented as an unexplored combinatorial approach applicable for multiple targets of inflammatory diseases, in order to perform controlled spatiotemporal enzymatic reactions and drug release in response to biologically relevant stimuli.

Bioinspired Metal-Free Fluorescent Carbon Nanozyme with Dual Catalytic Activity to Confront Cellular Oxidative Damage

Development of metal-free, recyclable enzyme mimics is challenging and requires key chemical modifications at the molecular level. Here, nitrilotriacetic acid-functionalized carbon nanospheres (LC-CNS@NTA) were prepared from the nitrogen-rich weed Lantana camara (LC) using a simple hydrothermal reaction condition. Transmission electron microscopy (TEM) studies revealed size of ∼160 ± 20 nm for LC-CNS@NTA whereas, the same showed fluorescence emission at ∼520 nm with a ∼63% quantum yield. Furthermore, LC-CNS@NTA showed strong peroxidase (Pxrd) activity toward a wide range of substrate viz., H₂O₂, 3,3',5,5'-tetramethylbenzidine, and o-phenylenediamine with K_m and V_max values of ∼257 μM and 1.06 μM/s, 282 μM and 1.47 μM/s, and 270.8 μM and 1.647 μM/s, respectively. Interestingly, this also showed catalase (CAT) activity against H₂O₂ with K_m and V_max values of ∼0.374 μM and 1.87 μM/s, respectively. It was observed that LC-CNS@NTA could effectively reduce the oxidative stress-induced cytotoxicity of HEK293 cells via retention of mitochondrial membrane potential, prevention of lipid peroxidation and DNA damage. It was further found that LC-CNS@NTA-treated cells showed reduced level of intracellular protein carbonylation and protein aggregation. The finding of the present study is expected to pave the path for designing engineered metal-free carbon nanozyme with dual enzyme mimic activity.

Atomic Engineering of Clusterzyme for Relieving Acute Neuroinflammation through Lattice Expansion

Natural enzymes are efficient and versatile biocatalysts but suffer in their environmental tolerance and catalytic stability. As artificial enzymes, nanozymes can improve the catalytic stability, but it is still a challenge to achieve high catalytic activity. Here, we employed atomic engineering to build the artificial enzyme named Au₂₄Ag₁ clusterzyme that hosts an ultrahigh catalytic activity as well as strong physiological stability via atom manipulation. The designed Au₂₄Ag₁ clusterzyme activates the Ag-S active site via lattice expansion in the oligomer atom layer, showing an antioxidant property 72 times higher than that of natural antioxidant Trolox. Enzyme-mimicked studies find that Au₂₄Ag₁ clusterzyme exhibits high catalase-like (CAT-like) and glutathione peroxidase-like (GPx-like) activity with a maximum reaction rate of 68.9 and 17.8 μM/min, respectively. Meanwhile, the unique catalytic landscape exhibits distinctive reactions against inflammation by inhibiting the cytokines at an early stage in the brain. Atomic engineering of clusterzymes provides a powerful and attractive platform with satisfactory atomic dispersion for tailoring biocatalysts freely at the atomic level.

Rational Design and Biological Application of Antioxidant Nanozymes

Nanozyme is a type of nanostructured material with intrinsic enzyme mimicking activity, which has been increasingly studied in the biological field. Compared with natural enzymes, nanozymes have many advantages, such as higher stability, higher design flexibility, and more economical production costs. Nanozymes can be used to mimic natural antioxidant enzymes to treat diseases caused by oxidative stress through reasonable design and modification. Oxidative stress is caused by imbalances in the production and elimination of reactive oxygen species (ROS) and reactive nitrogen species (RNS). This continuous oxidative stress can cause damage to some biomolecules and significant destruction to cell structure and function, leading to many physiological diseases. In this paper, the methods to improve the antioxidant properties of nanozymes were reviewed, and the applications of nanozyme antioxidant in the fields of anti-aging, cell protection, anti-inflammation, wound repair, cancer, traumatic brain injury, and nervous system diseases were introduced. Finally, the future challenges and prospects of nanozyme as an ideal antioxidant were discussed.

In vivo guiding inorganic nanozymes for biosensing and therapeutic potential in cancer, inflammation and microbial infections

Researchers have recently introduced some artificial enzymes based on nanomaterials that show significant catalytic activity relative to native enzymes called nanozyme. These nanozymes show superior performance than conventional catalysts and are considered as fascinating candidates for introducing the next generation of biomaterials in various industrial and biomedical fields. Recently, nanozymes have received a great deal of attention in biomedical applications due to their potential properties such as long-term stability, low cost, mass production capability, and controllable catalytic activity. Due to the intrinsic catalytic activity of nanoparticles (NPs) as nanozymes and their ability to be regulated in biomedical processes, this review paper focuses on the in vivo applications of nanozymes in biosensing and therapeutic activities. Despite the challenges and benefits of each approach, this paper attempts to provide an appropriate motivation for the classification of different nanozymes followed by their application in biomedical activities including in vivo biosensing and therapeutic potential in cancer, inflammation and microbial infections. Finally, some ongoing challenges and future perspective of nanozymes in biomedical application were surveyed. In conclusion, this paper may provide useful information regarding the development of nanozymes as promising platforms in biomedical settings due to expedited diagnosis, the advancement of multifactorial therapies and their pronounced stability.

Rational Design of Nanomaterials for Various Radiation-Induced Diseases Prevention and Treatment

Radiation treatments often unfavorably damage neighboring healthy organs and cause a series of radiation sequelae, such as radiation-induced hematopoietic system diseases, radiation-induced gastrointestinal diseases, radiation-induced lung diseases, and radiation-induced skin diseases. Recently, emerging nanomaterials have exhibited good superiority for these radiation-induced disease treatments. Given this background, the rational design principle of nanomaterials, which helps to optimize the therapeutic efficiency, has been an increasing need. Consequently, it is of great significance to perform a systematic summarization of the advances in this field, which can trigger the development of new high-performance nanoradioprotectors with drug efficiency maximization. Herein, this review highlights the advances and perspectives in the rational design of nanomaterials for preventing and treating various common radiation-induced diseases. Furthermore, the sources, clinical symptoms, and pathogenesis/injury mechanisms of these radiation-induced diseases will also be introduced. Furthermore, current challenges and directions for future efforts in this field are also discussed.

Nanozyme-based medicine for enzymatic therapy: progress and challenges

Nanozymes are nanomaterials with enzyme-like characteristics. As a new generation of artificial enzymes, nanozymes have the advantages of low cost, good stability, simple preparation, and easy storage, allowing them to overcome many of the limitations of natural enzymes in enzymatic therapy. Currently, most reported nanozymes exhibit oxidoreductase-like activities and can regulate redox balance in cells. Nanozymes with superoxide dismutase and catalase activity can be used to scavenge reactive oxygen species (ROS) for cell protection, while those with peroxidase and oxidase activity can generate ROS to kill harmful cells, such as tumor cells and bacteria. In this review, we summarize recent progress in nanozyme-based medicine for enzymatic therapy and highlight the opportunities and challenges in this field for future study.

Molybdenum disulfide-based materials with enzyme-like characteristics for biological applications

Nanozyme, a kind of nanomaterials with enzymatic activity, has been developing vigorously over the past years owing to its advantages such as low-cost, easy storage, ease of use in harsh environments and so on, compared with natural enzymes. At present, as a typical two-dimensional nanomaterial, molybdenum disulfide (MoS₂) and their hybrids with unexpected enzyme-like activities have caused wide attention. In this review, we mainly investigated the enzyme-like activities of MoS₂ based nanomaterials, including peroxidase-like activity, catalase-like activity and superoxide dismutase-like activity. Furthermore, we systematically introduce recent research progress of MoS₂ based nanomaterials in the fields of biological applications such as radiation protection, cancer therapy, antibacterial, and wound healing. Finally, the current challenges and perspectives of MoS₂ based nanomaterials in the future are also discussed and proposed. We expect this review may be significant to understand the properties of MoS₂ based nanomaterials and the development of two-dimensional nanomaterials with enzyme mimicking activities.

Biodegradable Self-Assembled Ultrasmall Nanodots as Reactive Oxygen/Nitrogen Species Scavengers for Theranostic Application in Acute Kidney Injury

Acute kidney injury (AKI) is frequently triggered by abundant reactive oxygen/nitrogen species (RONS) and leads to high morbidity and mortality in clinic. Unfortunately, the current clinical treatment options are only limited to supportive care, and hence, the development of nano-antioxidants with high kidney enrichment is an attractive novel strategy for AKI management. Herein, self-assembled ultrasmall nanodots are reported that consist of iron ion, gallic acid, and polyvinylpyrrolidone (denoted as FGP nanodots) as broad-spectrum RONS scavengers to alleviate both glycerinum- and cis-platinum- induced AKI in mice. Ultrasmall FGP nanodots (≈3.5 nm) offer efficient protection in vitro and reduce cellular apoptosis after H₂ O₂ stimulation by eliminating various RONS including hydroxyl radical (·OH), superoxide anion (·O₂^- ), nitric oxide (NO), and peroxynitrite (ONOO^- ), etc. In vivo duplex magnetic resonance/fluorescence imaging demonstrates preferential accumulation of FGP nanodots in the kidneys with rapid renal clearance through urine. Importantly, FGP nanodots exhibit remarkable RONS consumption in vivo with enhanced biocompatibility and biodegradability, resulting in superior therapeutic effect than small molecule drug (Amifostine) in two AKI mouse models. This study presents the promising potential of ultrasmall self-assembled FGP nanodots as imaging contrast agent and broad-spectrum antioxidant nanomedicine for AKI theranotics.

Catalytically potent and selective clusterzymes for modulation of neuroinflammation through single-atom substitutions

Emerging artificial enzymes with reprogrammed and augmented catalytic activity and substrate selectivity have long been pursued with sustained efforts. The majority of current candidates have rather poor catalytic activity compared with natural molecules. To tackle this limitation, we design artificial enzymes based on a structurally well-defined Au25 cluster, namely clusterzymes, which are endowed with intrinsic high catalytic activity and selectivity driven by single-atom substitutions with modulated bond lengths. Au24Cu1 and Au24Cd1 clusterzymes exhibit 137 and 160 times higher antioxidant capacities than natural trolox, respectively. Meanwhile, the clusterzymes demonstrate preferential enzyme-mimicking catalytic activities, with Au25, Au24Cu1 and Au24Cd1 displaying compelling selectivity in glutathione peroxidase-like (GPx-like), catalase-like (CAT-like) and superoxide dismutase-like (SOD-like) activities, respectively. Au24Cu1 decreases peroxide in injured brain via catalytic reactions, while Au24Cd1 preferentially uses superoxide and nitrogenous signal molecules as substrates, and significantly decreases inflammation factors, indicative of an important role in mitigating neuroinflammation.

Catalytic patch with redox Cr/CeO2 nanozyme of noninvasive intervention for brain trauma

Traumatic brain injury (TBI) is a sudden injury to the brain, accompanied by the production of large amounts of reactive oxygen and nitrogen species (RONS) and acute neuroinflammation responses. Although traditional pharmacotherapy can effectively decrease the immune response of neuron cells via scavenging free radicals, it always involves in short reaction time as well as rigorous clinical trial. Therefore, a noninvasive topical treatment method that effectively eliminates free radicals still needs further investigation. Methods: In this study, a type of catalytic patch based on nanozymes with the excellent multienzyme-like activity is designed for noninvasive treatment of TBI. The enzyme-like activity, free radical scavenging ability and therapeutic efficacy of the designed catalytic patch were assessed in vitro and in vivo. The structural composition was characterized by the X-ray diffraction, X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy technology. Results: Herein, the prepared Cr-doped CeO2 (Cr/CeO2) nanozyme increases the reduced Ce3+ states, resulting in its enzyme-like activity 3-5 times higher than undoped CeO2. Furthermore, Cr/CeO2 nanozyme can improve the survival rate of LPS induced neuron cells via decreasing excessive RONS. The in vivo experiments show the Cr/CeO2 nanozyme can promote wound healing and reduce neuroinflammation of mice following brain trauma. The catalytic patch based on nanozyme provides a noninvasive topical treatment route for TBI as well as other traumas diseases. Conclusions: The catalytic patch based on nanozyme provides a noninvasive topical treatment route for TBI as well as other traumas diseases.

In Vivo Neuroelectrophysiological Monitoring of Atomically Precise Au25 Clusters at an Ultrahigh Injected Dose

Atomically precise Au₂₅(SG)₁₈ clusters have shown great promise in near-infrared II cerebrovascular imaging, X-ray imaging, and cancer radiotherapy due to their high atomic number, unique molecular-like electronic structure, and renal clearable properties. Therefore, it is important to study the in vivo toxicity of Au₂₅ clusters. Unfortunately, previous toxicological investigations focused on low injected doses (<100 mg kg^-1) and routine research methods, such as blood chemistry and biochemistry, which cannot reflect neurotoxicity or tiny changes in neural activity. In this work, in vivo neuroelectrophysiology of Au₂₅ clusters at ultrahigh injected doses (200, 300, and 500 mg kg^-1) was investigated. Local field potential showed that the Au₂₅-treated mice showed a spike in delta rhythm and moved to lower frequency over time. The power spectrum showed a 38.3% reduction in the peak value at 10 h post-injection of Au₂₅ clusters compared with 3 h post-injection, which gradually became close to the normal level, indicating no permanent damage to the nervous system. Moreover, no significant structural changes were found in both neurons and glial cells at the histological level. These results of in vivo neuroelectrophysiology will encourage scientists to make more exciting discoveries on nervous system diseases by employing Au₂₅ clusters even at ultrahigh injected doses.

Heteroatom doped carbon dots with nanoenzyme like properties as theranostic platforms for free radical scavenging, imaging, and chemotherapy

Carbon-based artificial nanoenzymes have gained increasing interest as emerging and promising nanotheranostic agents due to their biocompatibility, low cost, and straightforward production. Herein, a multifunctional Mn, N, and S incorporated carbon dots (MnNS:CDs) nanoenzyme exhibiting scavenging activity against reactive oxygen species (ROS) and reactive nitrogen species (RNS), photoluminescence quantum yield of 17.7%, and magnetic resonance imaging (MRI) contrast was explored. The optical, magnetic, and antioxidant properties of MnNS:CDs were then regulated by control over Mn incorporation to achieve higher photostability and antioxidant properties. Furthermore, conjugation of MnNS:CDs with hyaluronic acid (HA) (denoted as MnNS:CDs@HA) endowed them with high biocompatibility, which is validated by in vivo studies on zebrafish, and the ability to specifically target cluster determinant 44 (CD44)-overexpressing B16F1 cells, as verified by in vitro confocal and MRI studies. The MnNS:CDs@HA probe with therapeutic antioxidant and dual-modal imaging capability was further assessed for non-covalent binding of doxorubicin (DOX) as a model chemotherapeutic cancer drug. Results showed that targeted delivery and pH-dependent release of DOX elicited apparent cell toxicity (90%) toward B16F1 cancer cells when compared to free DOX treatment group (60%). Benefiting from their intrinsic antioxidant properties, and dual-modal imaging ability, the MnNS:CDs@HA nanocarrier is projected to improve non-invasive targeted diagnosis and therapy. STATEMENT OF SIGNIFICANCE: Carbon dots (CDs) have gained increasing interest as emerging and promising artificial functional nanomaterials that mimic the structures and functions of natural enzymes. In this work, Mn, N, and S incorporated CDs (MnNS:CDs) were synthesized using a one-pot microwave hydrothermal method to serve as fluorescent and magnetic resonance imaging probes, and catalase mimics in the reduction of the oxidative-stress related damage. Further conjugation of the probes with hyaluronic acid endows them with a good in vitro and in vivo biocompatibility as well as the capability to selectively target CD44-overexpressing cancer cells, as investigated by in vitro fluorescence, and magnetic resonance imaging. The dual-modal nanoprobe was then used to carry on doxorubicin through a non-covalent association. Favorably, targeted delivery, and pH-responsive release of doxorubicin enhanced cell killing efficiency by 50% as opposed to the free doxorubicin treatment group. The presented theranostic heteroatom doped CDs hold great promise for dual-modal imaging enabling accurate diagnosis coupled with therapeutic effect through free radical scavenging and chemotherapy.

Hierarchically Porous S/N Codoped Carbon Nanozymes with Enhanced Peroxidase-like Activity for Total Antioxidant Capacity Biosensing

Design of highly active carbon nanozymes and further establishment of ultrasensitive biosensors remain a challenge. Herein, hierarchically porous carbon nanozymes with sulfur (S)/nitrogen (N) codoping (SNC) were developed. Compared with N-doped carbon (NC) nanozymes, SNC nanozymes have a smaller Michaelis-Menten constant and higher specific activities, demonstrating that the S-doping in SNC nanozymes could not only enhance their affinity toward substrates but also improve their catalytic performance. These results may be caused by the synergistic effect of heteroatoms (S and N). Because of the good enzyme-like activity, the proposed SNC nanozymes were exploited to the colorimetric detection of the total antioxidant capacity (TAC) using ascorbic acid as a typical model with a limit of detection of 0.08 mM. Because of its high sensitivity and selectivity and encouraging performance, the detection method presented practical feasibility for the TAC assay in commercial beverages. This work paves a way to design the highly active carbon nanozymes and expand their applications in the construction of high-performance biosensors.

Phenol-like group functionalized graphene quantum dots structurally mimicking natural antioxidants for highly efficient acute kidney injury treatment

Acute kidney injury (AKI) is a syndrome characterized by rapid loss of renal excretory function with high in-hospital mortality. The excess generation of reactive oxygen species (ROS) in the kidneys during AKI has been considered a major cause of renal failure. Currently available antioxidants for AKI treatment often lack the required antioxidative efficacy or renal accumulation rate. Herein, inspired by the structure of natural phenolic antioxidants, phenol-like group functionalized graphene quantum dots (h-GQDs) with both high ROS scavenging efficacy and renal specificity are constructed for AKI antioxidative therapy. Similar to natural polyphenols, the abundant phenol-like groups on h-GQDs are demonstrated to be the active components exerting antioxidative effects. Further exhaustive mechanistic investigations indicate that the ultrahigh antioxidative activity of h-GQDs originates not solely from the phenol-like groups, but also from the synergy between adjacent phenol-like groups, as well as the removal of unfavorable carbonyl groups on h-GQDs. In AKI mice, h-GQDs can effectively protect the kidneys from oxidative injury with only a one-sixteenth dose of the clinical antioxidant N-acetylcysteine (NAC) and show no evidence of toxicity. The findings of this study will facilitate development of high-performance carbon-based antioxidative platforms via structure–activity relationships for treating AKI and other ROS-related diseases.

Phenol-like group functionalized graphene quantum dots that structurally mimic natural antioxidants are constructed as high-efficacy reactive oxygen species scavengers for acute kidney injury antioxidative therapy.

Tailored Reconstituted Lipoprotein for Site-Specific and Mitochondria-Targeted Cyclosporine A Delivery to Treat Traumatic Brain Injury

The secondary damage in traumatic brain injury (TBI) can lead to lifelong disabilities, bringing enormous economic and psychological burden to patients and their families. Mitochondria, as the core mediator of the secondary injury cascade reaction in TBI, is an important target to prevent the spread of cell death and dysfunction. Thus, therapeutics that can accumulate at the damaged sites and subsequently rescue the functions of mitochondria would largely improve the outcome of TBI. Cyclosporine A (CsA), which can maintain the integrity of mitochondrial function, is among the most promising neuroprotective therapeutics for TBI treatment. However, the clinical application of CsA in TBI is largely hindered because of its poor access to the targets. Here, to realize targeted intracellular CsA delivery, we designed a lipoprotein biomimetic nanocarrier by incorporating CsA in the core and decorating a matrix metalloproteinase-9 activatable cell-penetrating peptide onto the surface of the lipoprotein-mimic nanocarrier. This CsA-loaded tailored reconstituted lipoprotein efficiently accumulated at the damaged brain sites, entered the target cells, bound to the membrane of mitochondria, more efficiently reduced neuronal damage, alleviated neuroinflammation, and rescued memory deficits at the dose 1/16 of free CsA in a controlled cortical impact injury mice model. The findings provide strong evidence that the secondary damages in TBI can be well controlled through targeted CsA delivery and highlight the potential of a lipoprotein biomimetic nanocarrier as a flexible nanoplatform for the management of TBI.

Ultrasmall Rhodium Nanozyme with RONS Scavenging and Photothermal Activities for Anti-Inflammation and Antitumor Theranostics of Colon Diseases

Colitis-associated colorectal cancer (CAC), in which chronic inflammation is a well-recognized carcinogen, requires concurrent anti-inflammation and antitumor treatments in the clinic. Herein, we report polyethylene glycol (PEG)-coated (PEGylated) ultrasmall rhodium nanodots (Rh-PEG NDs) can serve as a metallic nanozyme with reactive oxygen and nitrogen species (RONS) scavenging properties as well as photothermal activities for anti-inflammation and antitumor theranostics in colon diseases. Benefiting from multienzyme activities against RONS, Rh-PEG NDs can decrease the levels of pro-inflammatory cytokines (TNF-α, IL-6), resulting in good anti-inflammatory effect on dextran sulfate sodium-induced colitis. By virtue of high photothermal conversion efficiency (48.9%), Rh-PEG NDs demonstrate complete ablation of CT-26 colon tumor without any recurrence. Most importantly, Rh-PEG NDs exhibit good biocompatibility both at the cellular and animal levels. Our findings provide a paradigm to utilize metallic nanozymes for the potential management of colon diseases.

Enzyme-Like Properties of Gold Clusters for Biomedical Application

In recent years, the rapid development of nanoscience and technology has provided a new opportunity for the development and preparation of new inorganic enzymes. Nanozyme is a new generation of artificial mimetic enzyme, which like natural enzymes, can efficiently catalyze the substrate of enzyme under mild conditions, exhibiting catalytic efficiency, and enzymatic reaction kinetics similar to natural enzymes. However, nanozymes exist better stability than native enzymes, it can still maintain 85 % catalytic activity in strong acid and alkali (pH 2~10) or large temperature range (4~90°C). This provides conditions for designing complex catalytic systems. In this review, we discussed the enzymatic attributes and biomedical applications of gold nanoclusters, including peroxidase-like, catalase-like, detection of heavy metal ions, and therapy of brain and cancer etc. This review can help us understand the current research status nanozymes.

Clinically Approved Carbon Nanoparticles with Oral Administration for Intestinal Radioprotection via Protecting the Small Intestinal Crypt Stem Cells and Maintaining the Balance of Intestinal Flora

The exploration of an old drug for new biomedical applications has an absolute predominance in shortening the clinical conversion time of drugs for clinical application. In this work, carbon nanoparticles suspension injection (CNSI), the first clinically approved carbon nanoparticles in China, is explored as a new nano-radioprotective agent for potent intestinal radioprotection. CNSI shows powerful radioprotective performance in the intestine under oral administration, including efficient free radical scavenging ability, good biosafety, high chemical stability, and relatively long retention time. For example, CNSI shows high reactive oxygen species (ROS) scavenging activities, which effectively alleviates the mitochondrial dysfunction and DNA double-strand breaks to protect the cells against radiation-induced damage. Most importantly, this efficient ROS scavenging ability greatly helps restrain the apoptosis of the small intestinal epithelial and crypt stem cells, which decreases the damage of the mechanical barrier and thus relieves radiation enteritis. Moreover, CNSI helps remove the free radicals in the intestinal microenvironment and thus maintain the balance of intestinal flora so as to mitigate the radiation enteritis. The finding suggests a new application of clinically approved carbon nanoparticles, which not only promotes the development of new intestinal radioprotector, but also has a great potential for clinical transformation.

Antioxidants and Nanotechnology: Promises and Limits of Potentially Disruptive Approaches in the Treatment of Central Nervous System Diseases

Many central nervous system (CNS) diseases are still incurable and only symptomatic treatments are available. Oxidative stress is suggested to be a common hallmark, being able to cause and exacerbate the neuronal cell dysfunctions at the basis of these pathologies, such as mitochondrial impairments, accumulation of misfolded proteins, cell membrane damages, and apoptosis induction. Several antioxidant compounds are tested as potential countermeasures for CNS disorders, but their efficacy is often hindered by the loss of antioxidant properties due to enzymatic degradation, low bioavailability, poor water solubility, and insufficient blood-brain barrier crossing efficiency. To overcome the limitations of antioxidant molecules, exploitation of nanostructures, either for their delivery or with inherent antioxidant properties, is proposed. In this review, after a brief discussion concerning the role of the blood-brain barrier in the CNS and the involvement of oxidative stress in some neurodegenerative diseases, the most interesting research concerning the use of nano-antioxidants is introduced and discussed, focusing on the synthesis procedures, functionalization strategies, in vitro and in vivo tests, and on recent clinical trials.

Dual pH-triggered catalytic selective Mn clusters for cancer radiosensitization and radioprotection

Hypoxia is known to be a common feature within many types of solid tumors, which is closely related to the limited efficacy of radiotherapy. Meanwhile, due to the non-discriminatory killing effect of both normal and cancer cells during the radiation process, traditional radiosensitizers could bring severe non-negligible side-effects to the whole body. In this work, stable and atomically precise Mn clusters which possess efficient pH-triggered catalytic selective capacity are developed rationally. Mn clusters could efficiently catalyze oxygen production in an acidic tumor microenvironment, while exhibiting strong reducibility and free radical scavenging ability in neutral circumstances. In vivo experiments show that Mn clusters are able to enhance the radiotherapy effect in the mouse model of 4T1 tumors and protect normal tissues from radiation at the same time. Thus, the present work provides a novel dual-functional strategy to enhance radiotherapy-induced tumor treatment by improving tumor oxygenation and protect normal tissues from radiation simultaneously.

Carbon dot targeting to nitrogen signaling molecules for inhibiting neuronal death

Ultrasmall carbon dot with targeting ability to nitrogen signaling molecules inhibit neuronal death by regulating the activity of endogenous enzymes.

Applications of nanomaterials for scavenging reactive oxygen species in the treatment of central nervous system diseases

Nanomaterials with excellent ROS-scavenging ability and biodistribution are considered as promising candidates in alleviating oxidative stress and restoring redox balance in CNS diseases, further facilitating the function recovery of the CNS.