Hollow Prussian Blue Nanozymes Drive Neuroprotection against Ischemic Stroke via Attenuating Oxidative Stress, Counteracting Inflammation, and Suppressing Cell Apoptosis

Nanozymes: Potential Therapies for Reactive Oxygen Species Overproduction and Inflammation in Ischemic Stroke and Traumatic Brain Injury

Nanozymes, which can selectively scavenge reactive oxygen species (ROS), have recently emerged as promising candidates for treating ischemic stroke and traumatic brain injury (TBI) in preclinical models. ROS overproduction during the early phase of these diseases leads to oxidative brain damage, which has been a major cause of mortality worldwide. However, the clinical application of ROS-scavenging enzymes is limited by their short in vivo half-life and inability to cross the blood-brain barrier. Nanozymes, which mimic the catalytic function of natural enzymes, have several advantages, including cost-effectiveness, high stability, and easy storage. These advantages render them superior to natural enzymes for disease diagnosis and therapeutic interventions. This review highlights recent advancements in nanozyme applications for ischemic stroke and TBI, emphasizing their potential to mitigate the detrimental effect of ROS overproduction, oxidative brain damage, inflammation, and blood-brain barrier compromise. Therefore, nanozymes represent a promising treatment modality for ROS overproduction conditions in future medical practices.

Reduction of Oxidative Stress and Excitotoxicity by Mesenchymal Stem Cell Biomimetic Co-Delivery System for Cerebral Ischemia-Reperfusion Injury Treatment

A cerebral ischemia-reperfusion injury is ensued by an intricate interplay between various pathological processes including excitotoxicity, oxidative stress, inflammation, and apoptosis. For a long time, drug intervention policies targeting a single signaling pathway have failed to achieve the anticipated clinical efficacy in the intricate and dynamic inflammatory environment of the brain. Moreover, inadequate targeted drug delivery remains a significant challenge in cerebral ischemia-reperfusion injury therapy. In this study, a multifunctional nanoplatform (designated as PB-006@MSC) is developed using ZL006-loaded Prussian blue nanoparticles (PBNPs) camouflaged by a mesenchymal stem cell (MSC) membrane (MSCm). ZL006 is a neuroprotectant. It can be loaded efficiently into the free radical scavenger PBNP through mesoporous adsorption. This can simultaneously modulate multiple targets and pathways. MSCm biomimetics can reduce the nanoparticle immunogenicity, efficiently enhance their homing capability to the cerebral ischemic penumbra, and realize active-targeting therapy for ischemic stroke. In animal experiments, PB-006@MSC integrated reactive oxygen species (ROS) scavenging and neuroprotection. Thereby, it selectively targeted the cerebral ischemic penumbra (about fourfold higher accumulation at 24 h than in the non-targeted group), demonstrated a remarkable therapeutic efficacy in reducing the volume of cerebral infarction (from 37.1% to 2.3%), protected the neurogenic functions, and ameliorated the mortality.

Advances in metal-organic framework-based nanozymes in ROS scavenging medicine

Reactive oxygen species (ROS) play important roles in regulating various physiological functions in the human body, however, excessive ROS can cause serious damage to the human body, considering the various limitations of natural enzymes as scavengers of ROS in the body, the development of better materials for the scavenging of ROS is of great significance to the biomedical field, and nanozymes, as a kind of nanomaterials which can show the activity of natural enzymes. Have a good potential for the development in the area of ROS scavenging. Metal-organic frameworks (MOFs), which are porous crystalline materials with a periodic network structure composed of metal nodes and organic ligands, have been developed with a variety of active nanozymes including catalase-like, superoxide dismutase-like, and glutathione peroxidase-like enzymes due to the adjustability of active sites, structural diversity, excellent biocompatibility, and they have shown a wide range of applications and prospects. In the present review, we first introduce three representative natural enzymes for ROS scavenging in the human body, methods for the detection of relevant enzyme-like activities and mechanisms of enzyme-like clearance are discussed, meanwhile, we systematically summarize the progress of the research on MOF-based nanozymes, including the design strategy, mechanism of action, and medical application, etc. Finally, the current challenges of MOF-based nanozymes are summarized, and the future development direction is anticipated. We hope that this review can contribute to the research of MOF-based nanozymes in the medical field related to the scavenging of ROS.

Crystal Facet Controlled Metal-Support Interaction in Uricase Mimics for Highly Efficient Hyperuricemia Treatment

The effect of strong metal-support interaction (SMSI) has never been systematically studied in the field of nanozyme-based catalysis before. Herein, by coupling two different Pd crystal facets with MnO2, i.e., (100) by Pd cube (Pdc) and (111) by Pd icosahedron (Pdi), we observed the reconstruction of Pd atomic structure within the Pd-MnO2 interface, with the reconstructed Pdc (100) facet more disordered than Pdi (111), verifying the existence of SMSI in such coupled system. The rearranged Pd atoms in the interface resulted in enhanced uricase-like catalytic activity, with Pdc@MnO2 demonstrating the best catalytic performance. Theoretical calculations suggested that a more disordered Pd interface led to stronger interactions with intermediates during the uricolytic process. In vitro cell experiments and in vivo therapy results demonstrated excellent biocompatibility, therapeutic effect, and biosafety for their potential hyperuricemia treatment. Our work provides a brand-new perspective for the design of highly efficient uricase-mimic catalysts.

Inflammation in the Peripheral Nervous System after Injury

Nerve injury is a common condition that occurs as a result of trauma, iatrogenic injury, or long-lasting stimulation. Unlike the central nervous system (CNS), the peripheral nervous system (PNS) has a strong capacity for self-repair and regeneration. Peripheral nerve injury results in the degeneration of distal axons and myelin sheaths. Macrophages and Schwann cells (SCs) can phagocytose damaged cells. Wallerian degeneration (WD) makes the whole axon structure degenerate, creating a favorable regenerative environment for new axons. After nerve injury, macrophages, neutrophils and other cells are mobilized and recruited to the injury site to phagocytose necrotic cells and myelin debris. Pro-inflammatory and anti-inflammatory factors involved in the inflammatory response provide a favorable microenvironment for peripheral nerve regeneration and regulate the effects of inflammation on the body through relevant signaling pathways. Previously, inflammation was thought to be detrimental to the body, but further research has shown that appropriate inflammation promotes nerve regeneration, axon regeneration, and myelin formation. On the contrary, excessive inflammation can cause nerve tissue damage and pathological changes, and even lead to neurological diseases. Therefore, after nerve injury, various cells in the body interact with cytokines and chemokines to promote peripheral nerve repair and regeneration by inhibiting the negative effects of inflammation and harnessing the positive effects of inflammation in specific ways and at specific times. Understanding the interaction between neuroinflammation and nerve regeneration provides several therapeutic ideas to improve the inflammatory microenvironment and promote nerve regeneration.

Scale-Up Preparation of Manganese-Iron Prussian Blue Nanozymes as Potent Oral Nanomedicines for Acute Ulcerative Colitis

Prussian blue (PB) nanozymes are demonstrated as effective therapeutics for ulcerative colitis (UC), yet an unmet practical challenge remains in the scalable production of these nanozymes and uncertainty over their efficacy. With a novel approach, a series of porous manganese-iron PB (MnPB) colloids, which are shown to be efficient scavengers for reactive oxygen species (ROS) including hydroxyl radical, superoxide anion, and hydrogen peroxide, are prepared. In vitro cellular experiments confirm the capability of the nanozyme to protect cells from ROS attack. In vivo, the administration of MnPB nanozyme through gavage at a dosage of 10 mg kg-1 per day for three doses in total potently ameliorates the pathological symptoms of acute UC in a murine model, resulting in mitigated inflammatory responses and improved viability rate. Significantly, the nanozyme produced at a large scale can be achieved at an unprecedented yield weighting ≈11 g per batch of reaction, demonstrating comparable anti-ROS activities and treatment efficacy to its small-scale counterpart. This work represents the first demonstration of the scale-up preparation of PB analog nanozymes for UC without compromising treatment efficacy, laying the foundation for further testing of these nanozymes on larger animals and promising clinical translation.

Single-Atom-Based Nanoenzyme in Tissue Repair

Since the discovery of ferromagnetic nanoparticles Fe3O4 that exhibit enzyme-like activity in 2007, the research on nanoenzymes has made significant progress. With the in-depth study of various nanoenzymes and the rapid development of related nanotechnology, nanoenzymes have emerged as a promising alternative to natural enzymes. Within nanozymes, there is a category of metal-based single-atom nanozymes that has been rapidly developed due to low cast, convenient preparation, long storage, less immunogenicity, and especially higher efficiency. More importantly, single-atom nanozymes possess the capacity to scavenge reactive oxygen species through various mechanisms, which is beneficial in the tissue repair process. Herein, this paper systemically highlights the types of metal single-atom nanozymes, their catalytic mechanisms, and their recent applications in tissue repair. The existing challenges are identified and the prospects of future research on nanozymes composed of metallic nanomaterials are proposed. We hope this review will illuminate the potential of single-atom nanozymes in tissue repair, encouraging their sequential clinical translation.

Reactive oxygen/nitrogen species scavenging and inflammatory regulation by renal-targeted bio-inspired rhodium nanozymes for acute kidney injury theranostics

Acute kidney injury (AKI) results from the rapid deterioration of renal function, which is mainly treated by transplantation and dialysis, and has a high mortality rate. Inflammation induced by excess reactive oxygen/nitrogen species (RONS) plays a crucial role in AKI. Although small molecule antioxidants have been utilized to alleviate AKI, low bioavailability and side-effect of these drugs tremendously limit their clinical use. Hence, we successfully construct ultra-small (2-4 nm) rhodium nanoparticles modified with l-serine (denoted as Rh-Ser). Our results show that Rh-Ser with multiple enzyme-mimicking activities, allows remove various RONS to protect damaged kidney cells. Additionally, the ultrasmall size of Rh-Ser is conducive to enrichment in the renal tubules, and the modification of l-serine enables Rh-Ser to bind to kidney injury molecule-1, which is highly expressed on the surface of damaged renal cells, thereby targeting the damaged kidney and increasing the retention time. Moreover, Rh-Ser allows the production of oxygen at the inflammatory site, thus further improving hypoxia and inhibiting pro-inflammatory macrophages to relieve inflammation, and increasing the survival rate of AKI mice from 0 to 80%, which exhibits a better therapeutic effect than that of small molecule drug. Photoacoustic and fluorescence imaging can effectively monitor and evaluate the enrichment and therapeutic effect of Rh-Ser. Our study provides a promising strategy for the targeted treatment of AKI via RONS scavenging and inflammatory regulation.

Advancing stroke therapy: the potential of MOF-based nanozymes in biomedical applications

In this study, we explored the growing use of metal-organic framework (MOF)-based Nanozymes in biomedical research, with a specific emphasis on their applications in stroke therapy. We have discussed the complex nature of stroke pathophysiology, highlighting the crucial role of reactive oxygen species (ROS), and acknowledging the limitations of natural enzymes in addressing these challenges. We have also discussed the role of nanozymes, particularly those based on MOFs, their structural similarities to natural enzymes, and their potential to improve reactivity in various biomedical applications. The categorization of MOF nanozymes based on enzyme-mimicking activities is discussed, and their applications in stroke therapy are explored. We have reported the potential of MOF in treating stroke by regulating ROS levels, alleviation inflammation, and reducing neuron apoptosis. Additionally, we have addressed the challenges in developing efficient antioxidant nanozyme systems for stroke treatment. The review concludes with the promise of addressing these challenges and highlights the promising future of MOF nanozymes in diverse medical applications, particularly in the field of stroke treatment.

Polydopamine-modified black phosphorus nanosheet drug delivery system for the treatment of ischemic stroke

Black phosphorus (BP), as a representative metal-free semiconductor, has been extensively explored. It has a higher drug loading capacity in comparison to conventional materials and also possesses excellent biocompatibility and biodegradability. Furthermore, BP nanosheets can enhance the permeability of the blood-brain barrier (BBB) upon near-infrared (NIR) irradiation, owing to their photothermal effect. However, the inherent instability of BP poses a significant limitation, highlighting the importance of surface modification to enhance its stability. Ischemic stroke (IS) is caused by the occlusion of blood vessels, and its treatment is challenging due to the hindrance caused by the BBB. Therefore, there is an urgent need to identify improved methods for bypassing the BBB for more efficient IS treatment. This research devised a novel drug delivery approach based on pterostilbene (Pte) supported by BP nanosheets, modified with polydopamine (PDA) to form BP-Pte@PDA. This system shows robust stability and traverses the BBB using effective photothermal mechanisms. This enables the release of Pte upon pH and NIR stimuli, offering potential therapeutic advantages for treating IS. In a middle cerebral artery occlusion mouse model, the BP-Pte@PDA delivery system significantly reduced infarct size, and brain water content, improved neurological deficits, reduced the TLR4 inflammatory factor expression, and inhibited cell apoptosis. In summary, the drug delivery system fabricated in this study thus demonstrated good stability, therapeutic efficacy, and biocompatibility, rendering it suitable for clinical application.

Catalytic Nanoparticles in Biomedical Applications: Exploiting Advanced Nanozymes for Therapeutics and Diagnostics

Catalytic nanoparticles (CNPs) as heterogeneous catalyst reveals superior activity due to their physio-chemical features, such as high surface-to-volume ratio and unique optical, electric, and magnetic properties. The CNPs, based on their physio-chemical nature, can either increase the reactive oxygen species (ROS) level for tumor and antibacterial therapy or eliminate the ROS for cytoprotection, anti-inflammation, and anti-aging. In addition, the catalytic activity of nanozymes can specifically trigger a specific reaction accompanied by the optical feature change, presenting the feasibility of biosensor and bioimaging applications. Undoubtedly, CNPs play a pivotal role in pushing the evolution of technologies in medical and clinical fields, and advanced strategies and nanomaterials rely on the input of chemical experts to develop. Herein, a systematic and comprehensive review of the challenges and recent development of CNPs for biomedical applications is presented from the viewpoint of advanced nanomaterial with unique catalytic activity and additional functions. Furthermore, the biosafety issue of applying biodegradable and non-biodegradable nanozymes and future perspectives are critically discussed to guide a promising direction in developing span-new nanozymes and more intelligent strategies for overcoming the current clinical limitations.

Prussian blue analogues improves the microenvironment after spinal cord injury by regulating Zn

Mitochondrial injury, neuronal apoptosis and phenotypic transformation of macrophages are the main mechanisms of spinal cord injury. Based on the Prussian blue nanomase's strong ability to clear free radicals, the treatment of spinal cord injury with nano-zirconium (Pb-Zr) was carried out. The disease treatment strategy based on nanomaterials has excellent therapeutic effect, and Prussian blue analogs have good therapeutic properties, so the application prospects of Prussian blue analogs is broad. From the point of view of Prussian blue content, improving the presence of zirconium in the microenvironment significantly increased the activity of Prussian blue. Prussian Blue zirconium significantly improved lipopolysaccharide (LPS) and interferon (IFN-γ) induced neuronal cell (pc12 cells) and macrophage dysfunction by improving oxidative stress, inflammation, and apoptosis in the microenvironment. It can promote the recovery of motor function after spinal cord injury. In vivo experiments, it shows that Prussian blue zirconium can improve inflammation, apoptosis and oxidative stress of spinal cord tissue, promote regenerative therapy after spinal cord injury, and improve motor function. Moreover, it has been reported that high-priced Zr4+ cations can regulate the deposition and nucleation behavior of Zn2+ in high-performance zinc metal anodes. Therefore, we propose the hypothesis that Pb-Zr modulates Zn2+ be used to promote recovery from spinal cord injury. The results show that nanomaterial is beneficial in the treatment of spinal cord injury. This study provides a good prospect for the application of spinal cord injury treatment. It also provides an important feasibility for subsequent clinical conversions.

Advanced Nano-Drug Delivery Systems in the Treatment of Ischemic Stroke

In recent years, the frequency of strokes has been on the rise year by year and has become the second leading cause of death around the world, which is characterized by a high mortality rate, high recurrence rate, and high disability rate. Ischemic strokes account for a large percentage of strokes. A reperfusion injury in ischemic strokes is a complex cascade of oxidative stress, neuroinflammation, immune infiltration, and mitochondrial damage. Conventional treatments are ineffective, and the presence of the blood-brain barrier (BBB) leads to inefficient drug delivery utilization, so researchers are turning their attention to nano-drug delivery systems. Functionalized nano-drug delivery systems have been widely studied and applied to the study of cerebral ischemic diseases due to their favorable biocompatibility, high efficiency, strong specificity, and specific targeting ability. In this paper, we briefly describe the pathological process of reperfusion injuries in strokes and focus on the therapeutic research progress of nano-drug delivery systems in ischemic strokes, aiming to provide certain references to understand the progress of research on nano-drug delivery systems (NDDSs).

Protective effects of Prussian blue nanozyme against sepsis-induced acute lung injury by activating HO-1

Sepsis is a life-threatening condition involving dysfunctional organ responses stemming from dysregulated host immune reactions to various infections. The lungs are most prone to failure during sepsis, resulting in acute lung injury (ALI). ALI is associated with oxidative stress and inflammation, and current therapeutic strategies are limited. To develop a more specific treatment, this study aimed to synthesise Prussian blue nanozyme (PBzyme), which can reduce oxidative stress and inflammation, to alleviate ALI. PBzyme with good biosafety was synthesised using a modified hydrothermal method. PBzyme was revealed to be an activator of haem oxygenase-1 (HO-1), improving survival rate and ameliorating lung injury in mice. Zinc protoporphyrin, an inhibitor of HO-1, inhibited the prophylactic therapeutic efficacy of PBzyme on ALI, and affected the nuclear factor-κB signaling pathway and activity of HO-1. This study demonstrates that PBzyme can alleviate oxidative stress and inflammation through HO-1 and has a prophylactic therapeutic effect on ALI. This provides a new strategy and direction for the clinical treatment of sepsis-induced ALI.

Sustained release of vascular endothelial growth factor A and basic fibroblast growth factor from nanofiber membranes reduces oxygen/glucose deprivation-induced injury to neurovascular units

Upregulation of vascular endothelial growth factor A/basic fibroblast growth factor (VEGFA/bFGF) expression in the penumbra of cerebral ischemia can increase vascular volume, reduce lesion volume, and enhance neural cell proliferation and differentiation, thereby exerting neuroprotective effects. However, the beneficial effects of endogenous VEGFA/bFGF are limited as their expression is only transiently increased. In this study, we generated multilayered nanofiber membranes loaded with VEGFA/bFGF using layer-by-layer self-assembly and electrospinning techniques. We found that a membrane containing 10 layers had an ideal ultrastructure and could efficiently and stably release growth factors for more than 1 month. This 10-layered nanofiber membrane promoted brain microvascular endothelial cell tube formation and proliferation, inhibited neuronal apoptosis, upregulated the expression of tight junction proteins, and improved the viability of various cellular components of neurovascular units under conditions of oxygen/glucose deprivation. Furthermore, this nanofiber membrane decreased the expression of Janus kinase-2/signal transducer and activator of transcription-3 (JAK2/STAT3), Bax/Bcl-2, and cleaved caspase-3. Therefore, this nanofiber membrane exhibits a neuroprotective effect on oxygen/glucose-deprived neurovascular units by inhibiting the JAK2/STAT3 pathway.

Hybrid Hydrogels for Immunoregulation and Proangiogenesis through Mild Heat Stimulation to Accelerate Whole-Process Diabetic Wound Healing

Intense and persistent oxidative stress, excessive inflammation, and impaired angiogenesis severely hinder diabetic wound healing. Bioactive hydrogel dressings with immunoregulatory and proangiogenic properties have great promise in treating diabetic wounds. However, the therapeutic effects of dressings always depend on drugs with side effects, expensive cytokines, and cell therapies. Herein, a novel dynamic borate-bonds crosslinked hybrid multifunctional hydrogel dressings with photothermal properties are developed to regulate the microenvironment of diabetic wound sites and accelerate the whole process of its healing without additional medication. The hydrogel is composed of phenylboronic acid-modified chitosan and hyaluronic acid (HA) crosslinked by tannic acid (TA) through borate bonds and Prussian blue nanoparticles (PBNPs) with photothermal response characteristics are embedded in the polymer networks. The results indicate hydrogels show inherent broad-spectrum antioxidative activities through the integrated interaction of borate bonds, TA, and PBNPs. Meanwhile, combined with the regulation of macrophage phenotype by HA, the inflammatory microenvironment of diabetic wounds is transformed. Moreover, the angiogenesis is then enhanced by the mild photothermal effect of PBNPs, followed by promoted epithelialization and collagen deposition. In summary, this hybrid hydrogel system accelerates all stages of wound repair through antioxidative stress, immunomodulation, and proangiogenesis, showing great potential applications in diabetic wound management.

Salivary Amylase-Responsive Buccal Tablets Wipe Out Chemotherapy-Rooted Refractory Oral Mucositis

Oral mucositis (OM) is the most common and refractory complication of cancer chemotherapy and radiotherapy, severely affecting patients' life quality, lowering treatment tolerance, and discouraging patient compliance. Current OM delivery systems mostly affect the comfort of patient use and lead to poor compliance and unsatisfactory effects. Herein, salivary amylases (SAs)-responsive buccal tablets consisting of porous manganese-substituted Prussian blue (PMPB) nanocubes (NCs), anti-inflammatory apremilast (Apr) and starch controller have been engineered. PMPB NCs with large surface area can serve as carriers to load Apr, and their multienzyme-mimicking activity enables them to scavenge reactive oxygen species (ROS), which thus synergize with Apr to mitigate inflammation. More significantly, the starch controller can respond to abundant SAs in the oral cavity and realize the cascade, continuous, and complete drug release after enzymatic decomposition, which not only aids with high tissue affinity to prolong the resistance time but also improves the comfort of use. The preclinical study reveals that contributed by the above actions, such buccal tablets mitigate inflammation, promote endothelium proliferation and migration, and accelerate wound healing for repressing chemotherapy-originated intractable OM with positive oral microenvironment and shorter recovery time, thus holding high potentials in clinical translation.

Antioxidant nanozymes as next-generation therapeutics to free radical-mediated inflammatory diseases: A comprehensive review

Recent developments in exploring the biological enzyme mimicking properties in nanozymes have opened a separate avenue, which provides a suitable alternative to the natural antioxidants and enzymes. Due to high and tunable catalytic activity, low cost of synthesis, easy surface modification, and good biocompatibility, nanozymes have garnered significant research interest globally. Several inorganic nanomaterials have been investigated to exhibit catalytic activities of some of the key natural enzymes, including superoxide dismutase (SOD), catalase, glutathione peroxidase, peroxidase, and oxidase, etc. These nanozymes are used for diverse biomedical applications including therapeutics, imaging, and biosensing in various cells/tissues and animal models. In particular, inflammation-related diseases are closely associated with reactive oxygen and reactive nitrogen species, and therefore effective antioxidants could be excellent therapeutics due to their free radical scavenging ability. Although biological enzymes and other artificial antioxidants could perform well in scavenging the reactive oxygen and nitrogen species, however, suffer from several drawbacks such as the requirement of strict physiological conditions for enzymatic activity, limited stability in the environment beyond their optimum pH and temperature, and high cost of synthesis, purification, and storage make then unattractive for broad-spectrum applications. Therefore, this review systematically and comprehensively presents the free radical-mediated evolution of various inflammatory diseases (inflammatory bowel disease, mammary gland fibrosis, and inflammation, acute injury of the liver and kidney, mammary fibrosis, and cerebral ischemic stroke reperfusion) and their mitigation by various antioxidant nanozymes in the biological system. The mechanism of free radical scavenging by antioxidant nanozymes under in vitro and in vivo experimental models and catalytic efficiency comparison with corresponding natural enzymes has also been presented.

A Thrombin-Activated Peptide-Templated Nanozyme for Remedying Ischemic Stroke via Thrombolytic and Neuroprotective Actions

Ischemic stroke (IS) is one of the most common causes of disability and death. Thrombolysis and neuroprotection are two current major therapeutic strategies to overcome ischemic and reperfusion damage. In this work, a novel peptide-templated manganese dioxide nanozyme (PNzyme/MnO2 ) is designed that integrates the thrombolytic activity of functional peptides with the reactive oxygen species scavenging ability of nanozymes. Through self-assembled polypeptides that contain multiple functional motifs, the novel peptide-templated nanozyme is able to bind fibrin in the thrombus, cross the blood-brain barrier, and finally accumulate in the ischemic neuronal tissues, where the thrombolytic motif is "switched-on" by the action of thrombin. In mice and rat IS models, the PNzyme/MnO2 prolongs the blood-circulation time and exhibits strong thrombolytic action, and reduces the ischemic damages in brain tissues. Moreover, this peptide-templated nanozyme also effectively inhibits the activation of astrocytes and the secretion of proinflammatory cytokines. These data indicate that the rationally designed PNzyme/MnO2 nanozyme exerts both thrombolytic and neuroprotective actions. Giving its long half-life in the blood and ability to target brain thrombi, the biocompatible nanozyme may serve as a novel therapeutic agent to improve the efficacy and prevent secondary thrombosis during the treatment of IS.

Chuanzhitongluo Inhibits Neuronal Apoptosis in Mice with Acute Ischemic Stroke by Regulating the PI3K/AKT Signaling Pathway

BACKGROUND AND PURPOSE

Apoptosis is involved in the occurrence and development of acute ischemic stroke (AIS). This study aimed to assess whether Chuanzhitongluo (CZTL), a multi-target and multi-pathway compound preparation, plays a neuroprotective role in AIS by modulating neuronal apoptosis via the PI3K/AKT signaling pathway.

METHODS

A mouse model of AIS was established by photochemical processes. Cerebral infarction volume was measured by 2% staining with 2, 3, and 5-triphenyl tetrazole chloride (TTC). Neuron apoptosis was assessed by TUNEL staining. Apoptosis RNA arrays were used to detect changes in apoptosis-related gene expression profiles. Western blotting was used to detect proteins involved in the PI3K/AKT signaling pathway.

RESULTS

The study demonstrated that CZTL could potentially mitigate neuronal apoptosis in AIS mice. This appears to be achieved via the up-regulation of certain genes such as BCL-2, Birc6, and others, coupled with the down-regulation of genes like BAX, Bid, and Casp3. Further validation revealed that CZTL could enhance the expression of BCL-2 and reduce the expression of Cleaved Caspase-3 and BAX at both the gene and protein levels. The study also found that CZTL can enhance the phosphorylation level of the PI3K/AKT signaling pathway. In contrast to these findings, the PI3K inhibitor LY294002 notably amplified neuronal apoptosis in AIS mice.

CONCLUSIONS

These findings imply that CZTL's ability to inhibit neuronal apoptosis may be linked to the activation of AIS's PI3K/AKT signaling pathway.

Ultrasmall Cu2O@His Nanozymes with RONS Scavenging Capability for Anti-inflammatory Therapy

High concentrations of reactive oxygen and nitrogen species (RONS) are key characteristics of inflammatory sites. Scavenging RONS at the site of inflammation is an effective therapeutic strategy. This study introduces ultrasmall Cu2O@His nanoparticles with RONS-scavenging ability for the treatment of inflammatory bowel disease (IBD) in mice. The strong coordination between the nitrogen atom in histidine (His) and copper enhances the dispersion and stability of Cu2O@His. Due to their small size and large surface area, Cu2O@His exhibits outstanding RONS-clearing ability. Importantly, Cu2O@His can target mitochondrial sites and repair damaged mitochondria. With excellent dispersion and scavenging RONS ability, Cu2O@His demonstrates good efficacy in treating mouse IBD. This work provides a new paradigm for developing nanozymes with an ultrasmall size and multiple scavenging RONS abilities.

Recent Advances in Chemically Engineered Nanostructures Impact on Ischemic Stroke Treatment

Stroke is a serious public health problem that raises expenses for society and causes long-term impairment and death. However, due to restricted blood-brain barrier (BBB) penetration, there are few treatment alternatives for treating stroke. Recanalization techniques, neuroprotective medications, and recovery techniques are all forms of treatment. The ischemic stroke treatment window is too narrow for logical and efficient therapy, and detection is possible only in advanced stages. BBB integrity disruption, neurotoxicity, and the brief half-life of therapeutic thrombolytics are the key molecular pathogenic causes of ischemic stroke. Existing neuroprotective drugs' inability to promote the recovery of ischemic brain tissue after a stroke is another factor that contributes to the disease's progression, chronic nature, and severity. A possible approach to getting around these medication restrictions and boosting the effectiveness of therapies is nanotechnology. In order to get around these drug-related restrictions and boost the effectiveness of therapies for neurological conditions such as stroke, nanotechnology has emerged as a viable option. These problems might be avoided by using nanoparticle-based methods to create a thrombolytic medication that is safe to use after the tissue plasminogen activator (tPA) treatment window has passed. The idea of using biomimetic nanoparticles in the future for the treatment of ischemic stroke through immunotherapy and stem cell therapy is highlighted, along with recent advancements in the study of nanomaterials for ischemic stroke diagnostics and treatment.

Circ_0059662 exerts a positive role in oxygen-glucose deprivation/reoxygenation-induced SK-N-SH cell injury

Circular RNA (circRNA) is identified as a potential regulator of ischemic stroke (IS) progression. Through GEO database screening, it was found that circ_0059662 was highly expressed in acute IS patients. However, whether circ_0059662 participated in the IS process has not been studied. Oxygen-glucose deprivation/reoxygenation (OGD/R)-induced SK-N-SH cells were established to mimic IS cell models. The expression of circ_0059662, miR-579-3p, and ETS proto-oncogene 1 (ETS1) was measured via quantitative real-time PCR. Cell counting kit 8 assay, EdU assay and flow cytometry were utilized to detect cell proliferation and apoptosis. Western blot was employed to measure protein expression. ELISA was used to detect the levels of inflammation factors, and oxidative stress was determined by assessing SOD activity and MDA level. The relationship between miR-579-3p and circ_0059662 or ETS1 was examined via dual-luciferase reporter assay, RNA pull-down assay and RIP assay. Circ_0059662 was a circular RNA with highly expression in OGD/R-induced SK-N-SH cells. In OGD/R-induced cell injury, circ_0059662 knockdown promoted cell proliferation, and inhibited cell apoptosis, inflammation and oxidative stress. Circ_0059662 served as miR-579-3p sponge to positively regulate ETS1 expression. MiR-579-3p inhibitor and ETS1 overexpression could reverse the inhibition effect of circ_0059662 knockdown on OGD/R-induced cell injury. Besides, MiR-579-3p also could relieve OGD/R-induced SK-N-SH cell apoptosis, inflammation and oxidative stress by targeting ETS1. Our findings indicated that circ_0059662 knockdown alleviated OGD/R-induced SK-N-SH cell injury by sponging miR-579-3p to regulate ETS1 expression.

Nanozyme-Cosmetic Contact Lenses for Ocular Surface Disease Prevention

Efficiently balancing excess reactive oxygen species (ROS) caused by various factors on the ocular surface is a promising strategy for preventing the development of ocular surface diseases (OSDs). Nevertheless, the conventional topical administration of antioxidants is limited in efficacy due to poor absorption, rapid metabolism, and irreversible depletion, which impede their performance. To address this issue, contact lenses embedded with antioxidant nanozymes that can continuously scavenge ROS, thereby providing an excellent preventive effect against OSDs are developed. Specifically, Prussian blue family nanozymes are chosen based on their multiple antioxidant enzyme-like activities and excellent biocompatibility. The diverse range of colors made them promising candidates for the development of cosmetic contact lenses (CCLs) as a substitute for conventional pigments. The efficacy of nanozyme-CCLs is demonstrated in rabbits and rats exposed to a high risk of developing OSDs. These OSDs' prevention nanozyme-CCLs can pave the way for CCLs toward powerful wearable biomedical devices and provide novel strategies for the rational utilization of nanomaterials in clinical practice.

Tunable Sulfated Alginate-based Hydrogel Platform with enhanced anti-inflammatory and antioxidant capacity for promoting burn wound repair

Amidst progressive advancements in tissue engineering, there has been a significant enhancement in the efficacy of anti-inflammatory hydrogel dressings, addressing a myriad of clinical challenges on wound healing. A frequent complication during the initial stages of deep second-degree burn wound healing is the onset of an inflammatory storm, typically occurring without effective intervention. This event disrupts normal biological healing sequences, leading to undesirable regression. In response, we have customized a tunable, multidimensional anti-inflammatory hydrogel platform based on sulfated alginates (Algs), loaded with Prussian blue (PB) nanozymes. This platform competently eliminates surplus reactive oxygen species (ROS) present in the wound bed. Algs, functioning as a mimic of sulfated glycosaminoglycans (including heparin, heparan sulfate, and chondroitin sulfate) in the extracellular matrices (ECM), demonstrate a high affinity towards inflammatory chemokines such as interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1). This affinity effectively impedes the infiltration of inflammatory cells into the wound. Concurrently, Algs markedly modulate the macrophage phenotype transition from M1 to M2. Ultimately, our potent anti-inflammatory hydrogels, which strategically target inflammatory chemokines, M1 macrophages, and ROS, successfully attenuate dysregulated hyperinflammation in wound sites. Precise immunomodulation administered to deep second-degree burn wounds in mice has demonstrated promotion of neovascular maturation, granulation tissue formation, collagen deposition, and wound closure. Our biomimetic hydrogels, therefore, represent a significant expansion in the repertoire of anti-inflammatory strategies available for clinical practice.

Reactive oxygen nanobiocatalysts: activity-mechanism disclosures, catalytic center evolutions, and changing states

Benefiting from low costs, structural diversities, tunable catalytic activities, feasible modifications, and high stability compared to the natural enzymes, reactive oxygen nanobiocatalysts (RONBCs) have become dominant materials in catalyzing and mediating reactive oxygen species (ROS) for diverse biomedical and biological applications. Decoding the catalytic mechanism and structure-reactivity relationship of RONBCs is critical to guide their future developments. Here, this timely review comprehensively summarizes the recent breakthroughs and future trends in creating and decoding RONBCs. First, the fundamental classification, activity, detection method, and reaction mechanism for biocatalytic ROS generation and elimination have been systematically disclosed. Then, the merits, modulation strategies, structure evolutions, and state-of-art characterisation techniques for designing RONBCs have been briefly outlined. Thereafter, we thoroughly discuss different RONBCs based on the reported major material species, including metal compounds, carbon nanostructures, and organic networks. In particular, we offer particular insights into the coordination microenvironments, bond interactions, reaction pathways, and performance comparisons to disclose the structure-reactivity relationships and mechanisms. In the end, the future challenge and perspectives for RONBCs are also carefully summarised. We envision that this review will provide a comprehensive understanding and guidance for designing ROS-catalytic materials and stimulate the wide utilisation of RONBCs in diverse biomedical and biological applications.

A Redox Modulatory SOD Mimetic Nanozyme Prevents the Formation of Cytotoxic Peroxynitrite and Improves Nitric Oxide Bioavailability in Human Endothelial Cells

The endothelium-derived signalling molecule nitric oxide (NO) in addition to controlling multifarious servo-regulatory functions, suppresses key processes in vascular lesion formation and prevents atherogenesis and other vascular abnormalities. The conversion of NO into cytotoxic and powerful oxidant peroxynitrite (ONOO- ) in a superoxide (O2 .- )-rich environment has emerged as a major reason for reduced NO levels in vascular walls, leading to endothelial dysfunction and cardiovascular complications. So, designing superoxide dismutase (SOD) mimetics that can selectively catalyze the dismutation of O2 .- in the presence of NO, considering their rapid reaction is challenging and is of therapeutic relevance. Herein, the authors report that SOD mimetic cerium vanadate (CeVO4 ) nanozymes effectively regulate the bioavailability of both NO and O2 .- , the two vital constitutive molecules of vascular endothelium, even in the absence of cellular SOD enzyme. The nanozymes optimally modulate the O2 .- level in endothelial cells under oxidative stress conditions and improve endogenously generated NO levels by preventing the formation of ONOO- . Furthermore, nanoparticles exhibit size- and morphology-dependent uptake into the cells and internalize via the clathrin-mediated endocytosis pathway. Intravenous administration of CeVO4 nanoparticles in mice caused no definite organ toxicity and unaltered haematological and biochemical parameters, indicating their biosafety and potential use in biological applications.

Antioxidant nanozymes in kidney injury: mechanism and application

Excessive production of reactive oxygen species (ROS) in the kidneys is involved in the pathogenesis of kidney diseases, such as acute kidney injury (AKI) and diabetic kidney disease (DKD), and is the main reason for the progression of kidney injury. ROS can easily lead to lipid peroxidation and damage the tubular epithelial cell membrane, proteins and DNA, and other molecules, which can trigger cellular oxidative stress. Effective scavenging of ROS can delay or halt the progression of kidney injury by reducing inflammation and oxidative stress. With the development of nanotechnology and an improved understanding of nanomaterials, more researchers are applying nanomaterials with antioxidant activity to treat kidney injury. This article reviews the detailed mechanism between ROS and kidney injury, as well as the applications of nanozymes with antioxidant effects based on different materials for various kidney injuries. To better guide the applications of antioxidant nanozymes in kidney injury and other inflammatory diseases, at the end of this review we also summarize the aspects of nanozymes that need to be improved. An in-depth understanding of the role played by ROS in the occurrence and progression of kidney injury and the mechanism by which antioxidant nanozymes reduce oxidative stress is conducive to improving the therapeutic effect in kidney injury and inflammation-related diseases.

Antioxidant and Prooxidant Nanozymes: From Cellular Redox Regulation to Next-Generation Therapeutics

Nanozymes, nanomaterials with enzyme-mimicking activity, have attracted tremendous interest in recent years owing to their ability to replace natural enzymes in various biomedical applications, such as biosensing, therapeutics, drug delivery, and bioimaging. In particular, the nanozymes capable of regulating the cellular redox status by mimicking the antioxidant enzymes in mammalian cells are of great therapeutic significance in oxidative-stress-mediated disorders. As the distinction of physiological oxidative stress (oxidative eustress) and pathological oxidative stress (oxidative distress) occurs at a fine borderline, it is a great challenge to design nanozymes that can differentially sense the two extremes in cells, tissues and organs and mediate appropriate redox chemical reactions. In this Review, we summarize the advances in the development of redox-active nanozymes and their biomedical applications. We primarily highlight the therapeutic significance of the antioxidant and prooxidant nanozymes in various disease model systems, such as cancer, neurodegeneration, and cardiovascular diseases. The future perspectives of this emerging area of research and the challenges associated with the biomedical applications of nanozymes are described.

Engineered inhaled nanocatalytic therapy for ischemic cerebrovascular disease by inducing autophagy of abnormal mitochondria

Mitochondrial dysfunction and subsequent accumulation of reactive oxygen species (ROS) are key contributors to the pathology of ischemic cerebrovascular disease. Therefore, elimination of ROS and damaged mitochondria is crucial for the effective treatment of this disease. For this purpose, we designed an inhalation nanotherapeutic agent, P/D@Mn/Co3O4, to treat ischemic cerebrovascular disease. Mn/Co3O4 effectively removed excess ROS from cells, reduced acute cellular oxidative stress, and protected neural cells from apoptosis. Furthermore, it depleted the H+ surrounding mitochondria and depolarized the mitochondrial membrane potential, inducing mitophagy and eliminating abnormal mitochondria, thereby avoiding the continuous overproduction of ROS by eliminating the source of ROS regeneration. On intranasal administration, Mn/Co3O4 encapsulated by platelet membranes and 2,3-(dioxy propyl)-trimethylammonium chloride can bypass the blood-brain barrier, enter the brain through the trigeminal and olfactory pathways, and target inflammatory regions to remove ROS and damaged mitochondria from the lesion area. In rat models of stroke and vascular dementia, P/D@Mn/Co3O4 effectively inhibited the symptoms of acute and chronic cerebral ischemia by scavenging ROS and damaged mitochondria in the affected area. Our findings indicate that the nanotherapeutic agent developed in this study can be used for the effective treatment of ischemic cerebrovascular disease.

Prussian blue nanozymes: progress, challenges, and opportunities

Prussian Blue Nanozymes (PBNZs) have emerged as highly efficient agents for reactive oxygen species (ROS) elimination, owing to their multiple enzyme-like properties encompassing catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activities. As a functional nanomaterial mimicking enzyme, PBNZs not only surmount the limitations of natural enzymes, such as instability and high manufacturing costs, but also exhibit superior stability, tunable activity, low storage expenses, and remarkable reusability. Consequently, PBNZs have gained significant attention in diverse biomedical applications, including disease diagnosis and therapy. Over the past decade, propelled by advancements in catalysis science, biotechnology, computational science, and nanotechnology, PBNZs have witnessed remarkable progress in the exploration of their enzymatic activities, elucidation of catalytic mechanisms, and wide-ranging applications. This comprehensive review aims to provide a systematic overview of the discovery and catalytic mechanisms of PBNZ, along with the strategies employed to modulate their multiple enzyme-like activities. Furthermore, we extensively survey the recent advancements in utilizing PBNZs for scavenging ROS in various biomedical applications. Lastly, we analyze the existing challenges of translating PBNZs into therapeutic agents for clinical use and outline future research directions in this field. By presenting a comprehensive synopsis of the current state of knowledge, this review seeks to contribute to a deeper understanding of the immense potential of PBNZs as an innovative therapeutic agent in biomedicine.

Application of Nanozymes and its Progress in the Treatment of Ischemic Stroke

Nanozymes are a new kind of material which has been applied since the beginning of this century, and its birth has promoted the development of chemistry, materials science, and biology. Nanozymes can be used as a substitute for natural enzyme and has a wide range of applications; therefore, it has attracted extensive attention from all sectors of the community, and the number of studies has constantly increasing. In this paper, we introduced the outstanding achievements in the field of nanozymes in recent years from the main function, the construction of nanozyme-based biosensors, and the treatment of ischemic stroke, and we also illustrated the internal mechanism and the catalytic principle. In the end, the obstacles and challenges in the future development of nanozymes were proposed.

Prussian blue analog with separated active sites to catalyze water driven enhanced catalytic treatments

Chemodynamic therapy (CDT) uses the Fenton or Fenton-like reaction to yield toxic ‧OH following H2O2 → ‧OH for tumoral therapy. Unfortunately, H2O2 is often taken from the limited endogenous supply of H2O2 in cancer cells. A water oxidation CoFe Prussian blue (CFPB) nanoframes is presented to provide sustained, external energy-free self-supply of ‧OH from H2O to process CDT and/or photothermal therapy (PTT). Unexpectedly, the as-prepared CFPB nanocubes with no near-infrared (NIR) absorption is transformed into CFPB nanoframes with NIR absorption due to the increased Fe3+-N ≡ C-Fe2+ composition through the proposed proton-induced metal replacement reactions. Surprisingly, both the CFPB nanocubes and nanoframes provide for the self-supply of O2, H2O2, and ‧OH from H2O, with the nanoframe outperforming in the production of ‧OH. Simulation analysis indicates separated active sites in catalyzation of water oxidation, oxygen reduction, and Fenton-like reactions from CFPB. The liposome-covered CFPB nanoframes prepared for controllable water-driven CDT for male tumoral mice treatments.

Drug Delivery Strategies and Nanozyme Technologies to Overcome Limitations for Targeting Oxidative Stress in Osteoarthritis

Oxidative stress is an important, but elusive, therapeutic target for osteoarthritis (OA). Antioxidant strategies that target oxidative stress through the elimination of reactive oxygen species (ROS) have been widely evaluated for OA but are limited by the physiological characteristics of the joint. Current hallmarks in antioxidant treatment strategies include poor bioavailability, poor stability, and poor retention in the joint. For example, oral intake of exogenous antioxidants has limited access to the joint space, and intra-articular injections require frequent dosing to provide therapeutic effects. Advancements in ROS-scavenging nanomaterials, also known as nanozymes, leverage bioactive material properties to improve delivery and retention. Material properties of nanozymes can be tuned to overcome physiological barriers in the knee. However, the clinical application of these nanozymes is still limited, and studies to understand their utility in treating OA are still in their infancy. The objective of this review is to evaluate current antioxidant treatment strategies and the development of nanozymes as a potential alternative to conventional small molecules and enzymes.

Research Progress in Iron-Based Nanozymes: Catalytic Mechanisms, Classification, and Biomedical Applications

Natural enzymes are crucial in biological systems and widely used in biology and medicine, but their disadvantages, such as insufficient stability and high-cost, have limited their wide application. Since Fe₃O₄ nanoparticles were found to show peroxidase-like activity, researchers have designed and developed a growing number of nanozymes that mimic the activity of natural enzymes. Nanozymes can compensate for the defects of natural enzymes and show higher stability with lower cost. Iron, a nontoxic and low-cost transition metal, has been used to synthesize a variety of iron-based nanozymes with unique structural and physicochemical properties to obtain different enzymes mimicking catalytic properties. In this perspective, catalytic mechanisms, activity modulation, and their recent research progress in sensing, tumor therapy, and antibacterial and anti-inflammatory applications are systematically presented. The challenges and perspectives on the development of iron-based nanozymes are also analyzed and discussed.

Anti-inflammatory strategies for photothermal therapy of cancer

High temperature generated by photothermal therapy (PTT) can trigger an inflammatory response at the tumor site, which not only limits the efficacy of PTT but also increases the risk of tumor metastasis and recurrence. In light of the current limitations posed by inflammation in PTT, several studies have revealed that inhibiting PTT-induced inflammation can significantly improve the efficacy of cancer treatment. In this review, we summarize the research progress made in combining anti-inflammatory strategies to enhance the effectiveness of PTT. The goal is to offer valuable insights for developing better-designed photothermal agents in clinical cancer therapy.

A Bioinspired Manganese-Organic Framework Ameliorates Ischemic Stroke through its Intrinsic Nanozyme Activity and Upregulating Endogenous Antioxidant Enzymes

Following stroke, oxidative stress induced by reactive oxygen species (ROS) aggravates neuronal damage and enlarges ischemic penumbra, which is devastating to stroke patients. Nanozyme-based antioxidants are emerging to treat stroke through scavenging excessive ROS. However, most of nanozymes cannot efficiently scavenge ROS in neuronal cytosol and mitochondria, due to low-uptake abilities of neurons and barriers of organelle membranes, significantly limiting nanozymes' neuroprotective effects. To overcome this limitation, a manganese-organic framework modified with polydopamine (pDA-MNOF), capable of not only mimicking catalytic activities of natural SOD2's catalytic domain but also upregulating two endogenous antioxidant enzymes in neurons is fabricated. With such a dual anti-ROS effect, this nanozyme robustly decreases cellular ROS and effectively protects them from ROS-induced injury. STAT-3 signaling is found to play a vital role in pDA-MNOF activating the two antioxidant enzymes, HO1 and SOD2. In vivo pDA-MNOF treatment significantly improves the survival of middle cerebral artery occlusion (MCAo) mice by reducing infarct volume and more importantly, promotes animal behavioral recovery. Further, pDA-MNOF activates vascular endothelial growth factor expression, a downstream target of STAT3 signaling, thus enhancing angiogenesis. Taken together, the biochemical, cell-biological, and animal-level behavioral data demonstrate the potentiality of pDA-MNOF as a dual ROS-scavenging agent for stroke treatment.

Prussian blue nanozymes coated with Pluronic attenuate inflammatory osteoarthritis by blocking c-Jun N-terminal kinase phosphorylation

Osteoarthritis (OA) is a degenerative joint disorder associated with inflammation, functional disability, and high socioeconomic costs. The development of effective therapies against inflammatory OA has been limited owing to its complex and multifactorial nature. The efficacy of Prussian blue nanozymes coated with Pluronic (PPBzymes), US Food and Drug Administration-approved components, and their mechanisms of action have been described in this study, and PPBzymes have been characterized as a new OA therapeutic. Spherical PPBzymes were developed via nucleation and stabilization of Prussian blue inside Pluronic micelles. A uniformly distributed diameter of approximately 204 nm was obtained, which was maintained after storage in an aqueous solution and biological buffer. This indicates that PPBzymes are stable and could have biomedical applications. In vitro data revealed that PPBzymes promote cartilage generation and reduce cartilage degradation. Moreover, intra-articular injections with PPBzymes into mouse joints revealed their long-term stability and effective uptake into the cartilage matrix. Furthermore, intra-articular PPBzymes injections attenuated cartilage degradation without exhibiting cytotoxicity toward the synovial membrane, lungs, and liver. Notably, based on proteome microarray data, PPBzymes specifically block the JNK phosphorylation, which modulates inflammatory OA pathogenesis. These findings indicate that PPBzymes might represent a biocompatible and effective nanotherapeutic for obstructing JNK phosphorylation.

Engineering Single-Atom Nanozymes for Catalytic Biomedical Applications

Nanomaterials with enzyme-mimicking properties, coined as nanozymes, are a promising alternative to natural enzymes owing to their remarkable advantages, such as high stability, easy preparation, and favorable catalytic performance. Recently, with the rapid development of nanotechnology and characterization techniques, single atom nanozymes (SAzymes) with atomically dispersed active sites, well-defined electronic and geometric structures, tunable coordination environment, and maximum metal atom utilization are developed and exploited. With superior catalytic performance and selectivity, SAzymes have made impressive progress in biomedical applications and are expected to bridge the gap between artificial nanozymes and natural enzymes. Herein, the recent advances in SAzyme preparation methods, catalytic mechanisms, and biomedical applications are systematically summarized. Their biomedical applications in cancer therapy, oxidative stress cytoprotection, antibacterial therapy, and biosensing are discussed in depth. Furthermore, to appreciate these advances, the main challenges, and prospects for the future development of SAzymes are also outlined and highlighted in this review.

Modulation of macrophage polarization by iron-based nanoparticles

Macrophage polarization is an essential process involved in immune regulation. In response to different microenvironmental stimulation, macrophages polarize into cells with different phenotypes and functions, most typically M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophages. Iron-based nanoparticles have been widely explored and reported to regulate macrophage polarization for various biomedical applications. However, the influence factors and modulation mechanisms behind are complicated and not clear. In this review, we systemically summarized different iron-based nanoparticles that regulate macrophage polarization and function and discussed the influence factors and mechanisms underlying the modulation process. This review aims to deepen the understanding of the modulation of macrophage polarization by iron-based nanoparticles and expects to provide evidence and guidance for subsequent design and application of iron-based nanoparticles with specific macrophage modulation functions.

Neuroprotection of NAD+ and NBP against ischemia/reperfusion brain injury is associated with restoration of sirtuin-regulated metabolic homeostasis

Background: Ischemic stroke seriously threatens human health because of high rates of morbidity, mortality and disability. This study compared the effects of nicotinamide adenine dinucleotide (NAD+) and butylphthalide (NBP) on in vitro and in vivo ischemic stroke models.

Methods: Transient middle cerebral artery occlusion/reperfusion (t-MCAO/R) model was established in mice, and the cultured primary cortical neurons were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R). Cerebral infarct volume, neurobehavioral indices, antioxidant activity, ATP level and lactic acid content were determined. The neuroprotective effects of NAD+ or NBP were compared using sirtuin inhibitor niacinamide (NAM).

Results: Intraperitoneal injection of NBP within 4 h or intravenous injection of NAD+ within 1 h after t-MCAO/R significantly reduced the volume of infarcts, cerebral edema, and neurological deficits. Administration of NAD+ and NBP immediately after t-MCAO/R in mice showed similar neuroprotection against acute and long-term ischemic injury. Both NAD+ and NBP significantly inhibited the accumulation of MDA and H2O2 and reduced oxidative stress. NAD+ was superior to NBP in inhibiting lipid oxidation and DNA damage. Furthermore, although both NAD+ and NBP improved the morphology of mitochondrial damage induced by ischemia/reperfusion, NAD+ more effectively reversed the decrease of ATP and increase of lactic acid after ischemia/reperfusion compared with NBP. NAD+ but not NBP treatment significantly upregulated SIRT3 in the brain, but the sirtuin inhibitor NAM could abolish the protective effect of NAD+ and NBP by inhibiting SIRT1 or SIRT3.

Conclusions: These results confirmed the protective effects of NAD+ and NBP on cerebral ischemic injury. NBP and NAD+ showed similar antioxidant effects, while NAD+ had better ability in restoring energy metabolism, possibly through upregulating the activity of SIRT1 and SIRT3. The protection provided by NBP against cerebral ischemia/reperfusion may be achieved through SIRT1.

Self-actuated biomimetic nanocomposites for photothermal therapy and PD-L1 immunosuppression

Biomimetic nanocomposites are widely used in the biomedical field because they can effectively solve the problems existing in the current cancer treatment by realizing multi-mode collaborative treatment. In this study, we designed and synthesized a multifunctional therapeutic platform (PB/PM/HRP/Apt) with unique working mechanism and good tumor treatment effect. Prussian blue nanoparticles (PBs) with good photothermal conversion efficiency were used as nuclei and coated with platelet membrane (PM). The ability of platelets (PLTs) to specifically target cancer cells and inflammatory sites can effectively enhance PB accumulation at tumor sites. The surface of the synthesized nanocomposites was modified with horseradish peroxidase (HRP) to enhance the deep penetration of the nanocomposites in cancer cells. In addition, PD-L1 aptamer and 4T1 cell aptamer AS1411 were modified on the nanocomposite to achieve immunotherapy and enhance targeting. The particle size, UV absorption spectrum and Zeta potential of the biomimetic nanocomposite were determined by transmission electron microscope (TEM), Ultraviolet-visible (UV-Vis) spectrophotometer and nano-particle size meter, and the successful preparation was proved. In addition, the biomimetic nanocomposites were proved to have good photothermal properties by infrared thermography. The cytotoxicity test showed that it had a good killing ability of cancer cells. Finally, thermal imaging, tumor volume detection, immune factor detection and Haematoxilin-Eosin (HE) staining of mice showed that the biomimetic nanocomposites had good anti-tumor effect and could trigger immune response in vivo. Therefore, this biomimetic nanoplatform as a promising therapeutic strategy provides new inspiration for the current diagnosis and treatment of cancer.

Unveiling the Mechanism of Alleviating Ischemia Reperfusion Injury via a Layered Double Hydroxide-Based Nanozyme

Oxidative stress after ischemia reperfusion can cause irreversible brain damage. Thus, it is vital to timely consume excessive reactive oxygen species (ROS) and conduct molecular imaging monitoring on the brain injury site. However, previous studies have focused on how to scavenge ROS while ignoring the mechanism of relieving the reperfusion injury. Herein, we reported a layered double hydroxide (LDH)-based nanozyme (denoted as ALDzyme), which was fabricated by the confinement of astaxanthin (AST) with LDH. This ALDzyme can mimic natural enzymes, which include superoxide dismutase (SOD) and catalase (CAT). Furthermore, the SOD-like activity of ALDzyme is 16.3 times higher than that of CeO₂ (a typical ROS scavenger). Based on these enzyme-mimicking properties, this one-of-a-kind ALDzyme offers strong anti-oxidative properties as well as high biocompatibility. Importantly, this unique ALDzyme can establish an efficient magnetic resonance imaging platform, thus guiding the in vivo details. As a result, the infarct area can be reduced by 77% after reperfusion therapy, and the neurological impairment score can be lowered from 3-4 to 0-1. Density functional theory computations can reveal more about the mechanism of this ALDzyme's significant ROS consumption. These findings provide a method for unraveling the neuroprotection application process in ischemia reperfusion injury using an LDH-based nanozyme as a remedial nanoplatform.

Engineering ROS-scavenging Prussian blue nanozymes for efficient atherosclerosis nanotherapy

Atherosclerosis (AS), characterized by a chronic inflammatory disease, is a top cause of morbidity and disability worldwide. During the pathogenesis of AS, the leading process of inflammation highly involves a secondary event of oxidative stress, but limited antioxidants are currently available clinically due to their nonspecific effects, poor biosafety, and rapid in vivo elimination and urinary excretion as well as short retention time within plaque lesions. In this work, Prussian blue nanozymes with a strong reactive oxygen species (ROS)-scavenging ability were rationally engineered for efficient AS nanotherapy. Specifically, the obtained nanozymes with high photothermal performance could behave as potent photoacoustic imaging agents for plaque detection. In addition, these nanozymes featuring multienzyme activities could reduce the cellular ROS level, exert cytoprotective effects against ROS-mediated macrophages apoptosis, and inhibit foam cell formation, significantly boycotting AS development. The underlying mechanism was further verified by transcriptome sequencing at the cellular level and a series of immunohistochemical staining of aortic sinus sections in apoE^-/- mice. Finally, the high biocompatibility and biosafety of the engineered Prussian blue nanozymes further guarantee their clinical translation potential for AS management.

Progress in the preparation of Prussian blue-based nanomaterials for biomedical applications

Prussian blue (PB) is composed of the coordination network of Fe²⁺-CN-Fe³⁺ mixed valence state as a classic metal complex, which includes a C atom and Fe²⁺ (low spin), N atom and Fe³⁺ (high spin). PB and its analogues (PBA) have excellent biosafety, good magnetic properties, outstanding photothermal properties and the ability to mimic enzymatic behaviors due to their stable structure, tunable size, controllable morphology, abundant modification methods and excellent physicochemical properties. They have received increasing research interest and have shown promising applications in the biomedical field. Here, progress in the preparation of PB-based nanomaterials for biomedical applications is summarized and discussed. The preparation strategies, traditional synthesis and emerging preparation methods of PB are summarized systematically in this review. The design and preparation of PBA, PB(PBA)-based hollow structures and PB(PBA)-based composites are also included. While introducing the preparation status, some PB-based nanomaterials that have performed well in specific biomedical fields are emphasized. More importantly, the key factors and future development of PB for the clinical translation as multifunctional nanomaterials are also discussed. This review provides a reference for the design and biomedical application of PB-based nanomaterials.

Biomimetic Prussian blue nanozymes with enhanced bone marrow-targeting for treatment of radiation-induced hematopoietic injury

There is an urgent medical need to develop effective therapies that can ameliorate damage to the radiation-exposed hematopoietic system. Nanozymes with robust antioxidant properties have a therapeutic potential for mitigating radiation-induced hematopoietic injury. However, enhancing nanozyme recruitment to injured tissues in vivo while maintaining their catalytic activity remains a great challenge. Herein, we present the design and preparation of a biomimetic nanoparticle, a mesenchymal stem cell membrane camouflaged Prussian blue nanozyme (PB@MSCM), which exhibits biocompatible surface properties and demonstrates enhanced injury site-targeting towards the irradiated murine bone marrow niche. Notably, the constructed PB@MSCM possessed redox enzyme-mimic catalytic activity and could scavenge overproduced reactive oxygen species in the irradiated bone marrow cells, both in vitro and ex vivo. More importantly, the administration of PB@MSCM significantly mitigated hematopoietic cell apoptosis and accelerated the regeneration of hematopoietic stem and progenitor cells. Our findings provide a new targeted strategy to improve nanozyme therapy in vivo and mitigate radiation-induced hematopoietic injury.

Metal-organic framework-based nanoplatform enhance fibroblast activity to treat periodontitis

After periodontal tissue injury, reconstruct soft tissue sealing around the tooth surface is of fundamental importance to treat periodontitis. Among multiple cell types, fibroblast plays a central role in reestablishing functional periodontium. To enhance fibroblast activity, a novel metal-organic framework-based nanoplatform is fabricated using mesoporous Prussian blue (MPB) nanoparticles to load baicalein (BA), named MPB-BA. Drug release test displayed sustained BA release of MPB-BA. Cell proliferation, transwell migration and wound healing tests revealed accelerated fibroblast proliferation and migration for the established MPB-BA nanoplatform. Moreover, vinculin immunofluorescence staining, western blot and quantitative real-time PCR analysis showed up-regulated vinculin protein and integrin α5 and integrin β1 gene expressions for MPB-BA, suggesting improved cell adhesion. In addition, hematoxylin and eosin (H&E) and Masson trichromatic staining suggested superior anti-inflammatory and collagen fiber reconstruction effects for MPB-BA in a rat experimental periodontitis model in vivo. Our study may provide a promising strategy for the treatment of periodontitis.

NIR responsive nanoenzymes via photothermal ablation and hypoxia reversal to potentiate the STING-dependent innate antitumor immunity

Despite advances in combined photothermal/immunotherapy of tumor, the therapeutic effect has been impaired due to hypoxic microenvironment and inadequate immune activation. Manganese ions directly activated the stimulator of interferon genes (STING) pathway and induced innate antitumor immunity. Herein, a near infrared light (NIR)-responsive nanoenzyme (PB-Mn/OVA NE) was constructed by doping manganese into the ovalbumin (OVA)-templated Prussian blue (PB) nanoparticles. The resultant PB-Mn/OVA NEs exhibited favorable catalase activity to produce oxygen, which was conducive to alleviate the tumor hypoxic microenvironment. Under 808 ​nm NIR irradiation, the PB-Mn/OVA NEs with outstanding photothermal conversion efficiency of 30% significantly destroyed tumor cells by inducing immunogenic cell death (ICD). Impressively, the PB-Mn/OVA NEs could activate the cGAS-STING pathway to promote the maturation and the antigen cross-presentation ability of dendritic cells (DCs), which further activated cytotoxic T lymphocytes and memory T lymphocytes. Overall, this work presents a powerful nanoenzyme formula to integrate photothermal ablation and hypoxic reversal for triggering robust innate and adaptive antitumor immune response.