An Ultrasmall RuO2 Nanozyme Exhibiting Multienzyme-like Activity for the Prevention of Acute Kidney Injury

Renal-clearable and mitochondria-targeted metal-engineered carbon dot nanozymes for regulating mitochondrial oxidative stress in acute kidney injury

Mitochondrial dysfunction-induced oxidative stress is a key pathogenic factor in acute kidney injury (AKI). Despite this, current mitochondrial-targeted antioxidant therapies have shown limited efficacy in clinical settings. In this study, we introduce a novel renal-clearable and mitochondria-targeted antioxidant nanozyme (TPP@RuCDzyme) designed to precisely modulate mitochondrial oxidative stress and mitigate AKI progression. TPP@RuCDzyme was synthesized by integrating ruthenium-doped carbon dots (CDs) with triphenylphosphine (TPP), a mitochondria-targeting moiety. This nanozyme system exhibits cascade enzyme-like activities, mimicking superoxide dismutase (SOD) and catalase (CAT), to efficiently convert cytotoxic superoxide (O2•-) and hydrogen peroxide (H2O2) into non-toxic water (H2O) and oxygen (O2). This dual-enzyme mimicry effectively alleviates mitochondrial oxidative damage, restores mitochondrial function, and inhibits apoptosis. Compared to RuCDzyme alone, TPP@RuCDzyme demonstrated significantly enhanced efficacy in alleviating glycerol-induced AKI by inhibiting oxidative stress. By leveraging the catalytic activity derived from the integration of CDs and a metallic element, this study presents a promising therapeutic strategy for AKI and other renal diseases associated with mitochondrial dysfunction.

Neutrophil-like cell membrane-coated molybdenum-based nanoclusters for reduced oxidative stress and enhanced neurological recovery after intracerebral hemorrhage

Excessive reactive oxygen species (ROS) are detrimental to the brain that can result in neurological impairment and inhibiting neurological functionals recovery after intracerebral hemorrhage (ICH). However, there is still a lack of effective treatment for ICH, either with medicine or neurosurgery. Nanozymes with excellent superoxide dismutase and catalase properties can scavenge ROS and may provide therapeutic opportunities for ICH patients. However, the ability of nanozymes to non-invasively target cerebral hemorrhage lesions and further antioxidation effect are still unknown. Herein, neutrophile membrane-disguised molybdenum-based polyoxometalate nanozymes (POM@Mem) were developed to alleviate oxidative stress after ICH. Coating with neutrophil membrane allowed POM to target the hemorrhage sites and further inhibit ROS generation. POM@Mem can improve neuroinflammatory microenvironment and promote behavioral improvement of ICH mouse. Combining neutrophile membrane and nanozymes for targeting brain hemorrhage sites provides an effective strategy for the treatment of ICH. STATEMENT OF SIGNIFICANCE: Excessive reactive oxygen species (ROS) are detrimental to the brain and can lead to neurological impairment, hindering the recovery of neurological functions after intracerebral hemorrhage (ICH). Despite this, effective treatments for ICH, whether pharmaceuticals or neurosurgery, remain scarce. In this study, we developed neutrophil membrane-disguised molybdenum-based polyoxometalate nanozymes (POM@Mem) as a novel approach to alleviate oxidative stress following ICH. The neutrophil membrane coating enabled the POM nanozymes to specifically target hemorrhagic sites, thereby inhibiting ROS production. Additionally, POM@Mem improved the neuroinflammatory microenvironment and facilitated behavioral recovery in ICH mice. The combination of neutrophil membranes and nanozymes for targeted delivery to brain hemorrhage sites offers a promising strategy for the treatment of ICH.

Advances in Ultrasmall Inorganic Nanoparticles for Nanomedicine: From Diagnosis to Therapeutics

Inorganic nanoparticles possess unique physicochemical properties that make them attractive candidates for diverse applications in nanomedicine, including as contrast agents and as therapeutics. However, many inorganic nanoparticles are composed of high-atomic-number elements, raising safety concerns due to potential long-term retention in the body. However, ultrasmall inorganic nanoparticles (UINPs), i.e., those that are less than ∼5 nm in diameter, can offer the advantage of rapid renal clearance from the body, reducing toxicity risks associated with prolonged exposure and thereby creating a path toward clinical translation. In this review, we discuss current knowledge on the design and functionalization of UINPs, exploring their capabilities from diagnosis to therapeutics, with examples including radiosensitization, photothermal, and anti-inflammatory catalytic therapies. In addition, we discuss their limitations, the approaches taken to solve their limitations, and progress of UINPs toward clinical translation. Through this discussion, we aim to provide a comprehensive perspective on how UINPs are advancing the field of nanomedicine, underscoring their potential to significantly improve bioimaging and therapeutic outcomes.

Ultra-Small Iron-Based Nanoparticles with Mild Photothermal-Enhanced Cascade Enzyme-Mimic Reactions for Tumor Therapy

Chemodynamic therapy (CDT), which utilizes the catalytic reactions of nanoparticles to inhibit tumor growth, is a promising approach in cancer therapy. However, its efficacy is limited by insufficient hydrogen peroxide (H2O2) concentration in tumor microenvironments and unsatisfactory enzymatic catalytic activity. To overcome these limitations, ultra-small iron-based (USIB) nanoparticles with cascaded superoxide dismutase (SOD)-mimic and peroxidase (POD)-mimic activities have been engineered. USIB nanoparticles initiated by SOD-mimic activity to transform superoxide anions (O2·-) into H2O2, elevating H2O2 levels in the tumor microenvironment and subsequently utilizing POD-mimic activity to convert H2O2 into the more reactive ·OH, thereby achieving the destruction of tumor cells. In addition, USIB nanoparticles possess photothermal conversion capabilities, and their enzymatic activity can be significantly enhanced under mild laser irradiation. Therefore, by addressing the issues of insufficient substrate concentration and low enzymatic catalytic activity, the therapeutic efficiency of CDT has been improved. Our research integrates the cascade catalytic reactions of nanozymes with laser irradiation, effectively inhibiting tumor growth and exhibiting outstanding biosafety, demonstrating promising therapeutic potential.

Melanin-Deferoxamine Nanoparticles Targeting Ferroptosis Mitigate Acute Kidney Injury via RONS Scavenging and Iron Ion Chelation

Rhabdomyolysis (RM)-induced acute kidney injury (AKI) involves the release of large amounts of iron ions from excess myoglobin in the kidneys, which mediates the overproduction of reactive species with the onset of iron overload via the Fenton reaction, thus inducing ferroptosis and leading to renal dysfunction. Unfortunately, there are no effective treatments for AKI other than supportive care. Herein, we developed a multifunctional nanoplatform (MPD) by covalently bonding melanin nanoparticles (MP NPs) to deferoxamine. The nanoplatform has good dispersion and physiological stability, excellent chelating performance to iron ions, and broad-spectrum reactive species scavenging activity. Furthermore, cellular experiments showed that the NPs possessed high biocompatibility, antiapoptotic activity, antioxidant properties, and strong scavenging capacity of Fe2+ to mitigate iron overload, protecting the intracellular mitochondria from oxidative stress. Meanwhile, the intrinsic photoacoustic imaging capability of melanin allows the real-time monitoring of MPD NPs' target uptake and metabolic behavior in healthy and AKI mice. Most importantly, MPD NPs led to downregulation of the antioxidant pathway by targeting ferroptosis, thus effectively rescuing renal function in vivo, mitigating oxidative stress and inflammatory responses, and inhibiting renal tubular cell apoptosis. The nanoplatform offers a novel therapeutic strategy for RM-induced AKI.

Safety Landscape of Therapeutic Nanozymes and Future Research Directions

Oxidative stress and inflammation are at the root of a multitude of diseases. Treatment of these conditions is often necessary but current standard therapies to fight excessive reactive oxygen species (ROS) and inflammation are often ineffective or complicated by substantial safety concerns. Nanozymes are emerging nanomaterials with intrinsic enzyme-like properties that hold great promise for effective cancer treatment, bacterial elimination, and anti-inflammatory/anti-oxidant therapy. While there is rapid progress in tailoring their catalytic activities as evidenced by the recent integration of single-atom catalysts (SACs) to create next-generation nanozymes with superior activity, selectivity, and stability, a better understanding and tuning of their safety profile is imperative for successful clinical translation. This review outlines the current applied safety assessment approaches and provides a comprehensive summary of the safety knowledge of therapeutic nanozymes. Overall, nanozymes so far show good in vitro and in vivo biocompatibility despite considerable differences in their composition and enzymatic activities. However, current safety investigations mostly cover a limited set of basic toxicological endpoints, which do not allow for a thorough and deep assessment. Ultimately, remaining research gaps that should be carefully addressed in future studies are highlighted, to optimize the safety profile of therapeutic nanozymes early in their pre-clinical development.

Nanocarrier-Based Drug Delivery Systems Targeting Kidney Diseases

BACKGROUND

The potential applications of nanotechnology in the medical field have become increasingly recognized in recent years. Nanocarriers have emerged as a versatile tool, offering a wide range of applications due to their unique properties. In addition to the targeted drugs delivery, nanocarriers have also proven to be extremely effective in imaging and diagnostics. Continuous advances in nanotechnology have paved the way for innovative solutions to complex challenges in human health, shaping the future of nanotechnology and its applications.

SUMMARY

By exploring different types of nanoparticles, this review delves into the different characteristics that can be tailored to enhance their kidney access. Although the structural complexity of the kidney may prevent nanocarriers passage, optimization of nanocarrier characteristics such as shape, size, charge, and surface modifications may overcome these barriers, allowing for targeted delivery. By harnessing the potential of nanoparticles, researchers aim to develop targeted and efficient therapies that can address various kidney-related disorders.

KEY MESSAGES

This review highlights the promising advancements in nanotechnology and their potential impact on improving the therapeutic outcomes for several kidney diseases.

Recent Progress on Peroxidase Modification and Application

Peroxdiase is one of the member of oxireductase super family, which has a broad substrate range and a variety of reaction types, including hydroxylation, epoxidation or halogenation of unactivated C-H bonds, and aromatic group or biophenol compounds. Here, we summarized the recently discovered enzymes with peroxidation activity, and focused on the special structures, sites, and corresponding strategies that can change the peroxidase catalytic activity, stability, and substrate range. The comparison of the structural differences between these natural enzymes and the mimic enzymes of binding nanomaterials and polymer materials is helpful to expand the application of peroxidase in industry. In addition, we also reviewed the catalytic application of peroxidase in the synthesis of important organic molecules and the degradation of pollutants.

Engineering the nanozyme hydrogel beads by polyvinyl alcohol/chitosan encapsulation with recyclable and sustainable catalytic activity for visual analysis of hydrogen peroxide

BACKGROUND

Hydrogen peroxide (H2O2) plays a vital role in human health and have been regarded as a crucial analyte in metabolic processes, redox transformations, foods research and medical fields. Especially, the long-time and excessive digestion of H2O2 may even cause severe diseases. Although conventional instrumental methods and nanozymes-based colorimetric methods have been developed to accomplish the quantitative analysis of H2O2, the drawbacks of instrument dependence, cost-effectiveness, short lifespan, non-portable and unsustainable detection efficacies will limit their applications in different detection scenarios.

RESULTS

Herein, to address these challenges, we have proposed a novel strategy for nanozyme (RuO2) hydrogel preparation by the solid support from cross-linked polyvinyl alcohol (PVA) and chitosan (CS) to both inherit the dominant peroxidase-like (POD) activity and protect the RuO2 from losing efficacies. Taking advantages from the hydrogel, the encapsulated RuO2 were further prepared as the regularly spherical beads (PCRO) to exhibit the sustainable, recyclable, and robust catalysis. Moreover, the intrinsic color interferences which originated from RuO2 can be avoided by the encapsulation strategy to promote the detection accuracy. Meanwhile, the high mechanical strength of PCRO shows the high stability, reproducibility, and cyclic catalysis to achieve the recyclable detection performance and long lifetime storage (40 days), which enables the sensitively detection of H2O2 with the detection limit as lower to 15 μM and the wide detection linear range from 0.025 to 1.0 mM.

SIGNIFICANCE

On the basis of the unique properties, PCRO has been further adopted to construct a smartphone detection platform to realize the instrument-free and visual analysis of H2O2 in multi-types of milk and real water samples through capturing, processing, and analyzing the RGB values from the colorimetric photographs. Therefore, PCRO with the advanced detection efficacies holds the great potential in achieving the portable and on-site analysis of targets-of-interest.

Rational design of Au-Bi bimetallic nanozyme for NIR-II laser mediated multifunctional combined tumor therapy

To maximize the therapeutic effects and minimize the adverse effects of synergistic tumor therapies, a multifunctional nanozyme Au-Bi/ZIF-8@DOX@HA (ABZ@DOX@HA) was designed and synthesized through the Au and Bi bimetallic doping of ZIF-8, loading of the DOX, and modifying with hyaluronic acid (HA). The ABZ@DOX@HA nanoparticles (NPs) could simulate the enzymatic activities of glucose oxidase (GOx) and peroxidase (POD). Upon irradiated by near-infrared region (NIR-II) laser, the strong synergism of the photothermal abilities of the loaded Au and Bi nanodots accelerated the collapse of the ABZ structure at the tumor site considerably and released Au, Bi nanodots and DOX. The results in vitro and in vivo proved that ABZ@DOX@HA nanozyme could effectively exert the combined tumor therapy of starvation treatment, photothermal therapy (PTT), chemodynamic therapy (CDT) and chemotherapy. The current research provides a new strategy to address the inherent challenges of easy clearance and short blood circulation of small-sized NPs during the treatment of tumors with nanomedicine, as well as the aggregation and oxidation of inorganic nanodots.

Application of multimodal ultrasonography to predicting the acute kidney injury risk of patients with sepsis: artificial intelligence approach

The occurrence of acute kidney injury in sepsis represents a common complication in hospitalized and critically injured patients, which is usually associated with an inauspicious prognosis. Thus, additional consequences, for instance, the risk of developing chronic kidney disease, can be coupled with significantly higher mortality. To intervene in advance in high-risk patients, improve poor prognosis, and further enhance the success rate of resuscitation, a diagnostic grading standard of acute kidney injury is employed to quantify. In the article, an artificial intelligence-based multimodal ultrasound imaging technique is conceived by incorporating conventional ultrasound, ultrasonography, and shear wave elastography examination approaches. The acquired focal lesion images in the kidney lumen are mapped into a knowledge map and then injected into feature mining of a multicenter clinical dataset to accomplish risk prediction for the occurrence of acute kidney injury. The clinical decision curve demonstrated that applying the constructed model can help patients whose threshold values range between 0.017 and 0.89 probabilities. Additionally, the metrics of model sensitivity, specificity, accuracy, and area under the curve (AUC) are computed as 67.9%, 82.48%, 76.86%, and 0.692%, respectively, which confirms that multimodal ultrasonography not only improves the diagnostic sensitivity of the constructed model but also dramatically raises the risk prediction capability, thus illustrating that the predictive model possesses promising validity and accuracy metrics.

Activation of the PPARγ/NF-κB pathway by A-MPDA@Fe3O4@PVP via scavenging reactive oxygen species to alleviate hepatic ischemia-reperfusion injury

Hepatic ischemia-reperfusion injury (IRI) is a common pathological process during hepatectomy and liver transplantation and the two primary reasons for hepatic IRI are reactive oxygen species (ROS)-mediated oxidative stress and excessive inflammatory responses. Herein, a novel antioxidant nanodrug (A-MPDA@Fe3O4@PVP) is prepared by employing L-arginine-doped mesoporous polydopamine (A-MPDA) nanoparticles as the carrier for deposition of ultra-small ferric oxide (Fe3O4) nanoparticles and further surface modification with polyvinylpyrrolidone (PVP). A-MPDA@Fe3O4@PVP not only effectively reduces the aggregation of ultra-small Fe3O4, but also simultaneously replicates the catalytic activity of catalase (CAT) and superoxide dismutase (SOD). A-MPDA@Fe3O4@PVP with good antioxidant activity can rapidly remove various toxic reactive oxygen species (ROS) and effectively regulate macrophage polarization in vitro. In the treatment of hepatic IRI, A-MPDA@Fe3O4@PVP effectively alleviates ROS-induced oxidative stress, reduces the expression of inflammatory factors, and prevents apoptosis of hepatocytes through immune regulation. A-MPDA@Fe3O4@PVP can further protect liver tissue by activating the PPARγ/NF-κB pathway. This multiplex antioxidant enzyme therapy can provide new references for the treatment of IRI in organ transplantation and other ROS-related injuries such as fibrosis, cirrhosis, and bacterial and hepatic viral infection.

Metal-Drug Coordination Nanoparticles and Hydrogels for Enhanced Delivery

Drug delivery is a key component of nanomedicine, and conventional delivery relies on the adsorption or encapsulation of drug molecules to a nanomaterial. Many delivery vehicles contain metal ions, such as metal-organic frameworks, metal oxides, transition metal dichalcogenides, MXene, and noble metal nanoparticles. These materials have a high metal content and pose potential long-term toxicity concerns leading to difficulties for clinical approval. In this review, recent developments are summarized in the use of drug molecules as ligands for metal coordination forming various nanomaterials and soft materials. In these cases, the drug-to-metal ratio is much higher than conventional adsorption-based strategies. The drug molecules are divided into small-molecule drugs, nucleic acids, and proteins. The formed hybrid materials mainly include nanoparticles and hydrogels, upon which targeting ligands can be grafted to improve efficacy and further decrease toxicity. The application of these materials for addressing cancer, viral infection, bacterial infection inflammatory bowel disease, and bone diseases is reviewed. In the end, some future directions are discussed from fundamental research, materials science, and medicine.

Physiological principles underlying the kidney targeting of renal nanomedicines

Kidney disease affects more than 10% of the global population and is associated with considerable morbidity and mortality, highlighting a need for new therapeutic options. Engineered nanoparticles for the treatment of kidney diseases (renal nanomedicines) represent one such option, enabling the delivery of targeted therapeutics to specific regions of the kidney. Although they are underdeveloped compared with nanomedicines for diseases such as cancer, findings from preclinical studies suggest that renal nanomedicines may hold promise. However, the physiological principles that govern the in vivo transport and interactions of renal nanomedicines differ from those of cancer nanomedicines, and thus a comprehensive understanding of these principles is needed to design nanomedicines that effectively and specifically target the kidney while ensuring biosafety in their future clinical translation. Herein, we summarize the current understanding of factors that influence the glomerular filtration, tubular uptake, tubular secretion and extrusion of nanoparticles, including size and charge dependency, and the role of specific transporters and processes such as endocytosis. We also describe how the transport and uptake of nanoparticles is altered by kidney disease and discuss strategic approaches by which nanoparticles may be harnessed for the detection and treatment of a variety of kidney diseases.

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.

pH-Activatable Pre-Nanozyme Mediated H2S Delivery for Endo-Exogenous Regulation of Oxidative Stress in Acute Kidney Injury

Oxidative stress induced by excess reactive oxygen species (ROS) is a primary pathogenic cause of acute kidney injury (AKI). Development of an effective antioxidation system to mitigate oxidative stress for alleviating AKI remains to be investigated. This study presents the synthesis of an ultra-small Platinum (Pt) sulfur cluster (Pt5.65S), which functions as a pH-activatable prefabricated nanozyme (pre-nanozyme). This pre-nanozyme releases hydrogen sulfide (H2S) and transforms into a nanozyme (Ptzyme) that mimics various antioxidant enzymes, including superoxide dismutase and catalase, within the inflammatory microenvironment. Notably, the Pt5.65S pre-nanozyme exhibits an endo-exogenous synergy-enhanced antioxidant therapeutic mechanism. The Ptzyme reduces oxidative damage and inflammation, while the released H2S gas promotes proneurogenesis by activating Nrf2 and upregulating the expression of antioxidant molecules and enzymes. Consequently, the Pt5.65S pre-nanozyme shows cytoprotective effects against ROS/reactive nitrogen species (RNS)-mediated damage at remarkably low doses, significantly improving treatment efficacy in mouse models of kidney ischemia-reperfusion injury and cisplatin-induced AKI. Based on these findings, the H2S-generating pre-nanozyme may represent a promising therapeutic strategy for mitigating inflammatory diseases such as AKI and others.

Mesoscale size-promoted targeted therapy for acute kidney injury through combined RONS scavenging and inflammation alleviation strategy

Acute kidney injury (AKI) is a heterogeneous, high-mortality clinical syndrome with diverse pathogenesis and prognosis, but it lacks the effective therapy clinically. Its pathogenesis is associated with production of reactive oxygen/nitrogen species and infiltration of inflammatory cells. To overcome these pathogenic factors and improve the therapeutic efficiency, we synthesized triptolide-loaded mesoscale polydopamine melanin-mimetic nanoparticles (MeNP4TP) as the antioxidant plus anti-inflammatory therapeutic platform to synergistically scavenge reactive oxygen/nitrogen species (RONS), inhibit the activity of macrophages and dendritic cells, and generate Treg cells for AKI therapy. It was demonstrated that mesoscale size was beneficial for MeNP4TP to specifically accumulate at renal tubule cells, and MeNP4TP could significantly attenuate oxidative stress, reduce proinflammatory immune cells in renal, and repair renal function in cisplatin-induced AKI mouse model. MeNP4TP might be a potential candidate to inhibit oxidative damages and inflammatory events in AKI.

Neuromodulation by nanozymes and ultrasound during Alzheimer's disease management

Alzheimer's disease (AD) is a neurodegenerative disorder with complex pathogenesis and effective clinical treatment strategies for this disease remain elusive. Interestingly, nanomedicines are under extensive investigation for AD management. Currently, existing redox molecules show highly bioactive property but suffer from instability and high production costs, limiting clinical application for neurological diseases. Compared with natural enzymes, artificial enzymes show high stability, long-lasting catalytic activity, and versatile enzyme-like properties. Further, the selectivity and performance of artificial enzymes can be modulated for neuroinflammation treatments through external stimuli. In this review, we focus on the latest developments of metal, metal oxide, carbon-based and polymer based nanozymes and their catalytic mechanisms. Recent developments in nanozymes for diagnosing and treating AD are emphasized, especially focusing on their potential to regulate pathogenic factors and target sites. Various applications of nanozymes with different stimuli-responsive features were discussed, particularly focusing on nanozymes for treating oxidative stress-related neurological diseases. Noninvasiveness and focused application to deep body regions makes ultrasound (US) an attractive trigger mechanism for nanomedicine. Since a complete cure for AD remains distant, this review outlines the potential of US responsive nanozymes to develop future therapeutic approaches for this chronic neurodegenerative disease and its emergence in AD management.

Recent Advances in Nanomaterials for the Treatment of Acute Kidney Injury

Acute kidney injury (AKI) is a serious clinical syndrome with high morbidity, elevated mortality, and poor prognosis, commonly considered a "sword of Damocles" for hospitalized patients, especially those in intensive care units. Oxidative stress, inflammation, and apoptosis, caused by the excessive production of reactive oxygen species (ROS), play a key role in AKI progression. Hence, the investigation of effective and safe antioxidants and inflammatory regulators to scavenge overexpressed ROS and regulate excessive inflammation has become a promising therapeutic option. However, the unique physiological structure and complex pathological alterations in the kidneys render traditional therapies ineffective, impeding the residence and efficacy of most antioxidant and anti-inflammatory small molecule drugs within the renal milieu. Recently, nanotherapeutic interventions have emerged as a promising and prospective strategy for AKI, overcoming traditional treatment dilemmas through alterations in size, shape, charge, and surface modifications. This Review succinctly summarizes the latest advancements in nanotherapeutic approaches for AKI, encompassing nanozymes, ROS scavenger nanomaterials, MSC-EVs, and nanomaterials loaded with antioxidants and inflammatory regulator. Following this, strategies aimed at enhancing biocompatibility and kidney targeting are introduced. Furthermore, a brief discussion on the current challenges and future prospects in this research field is presented, providing a comprehensive overview of the evolving landscape of nanotherapeutic interventions for AKI.

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.

Multienzyme-Like Nanozymes: Regulation, Rational Design, and Application

Nanomaterials with more than one enzyme-like activity are termed multienzymic nanozymes, and they have received increasing attention in recent years and hold huge potential to be applied in diverse fields, especially for biosensing and therapeutics. Compared to single enzyme-like nanozymes, multienzymic nanozymes offer various unique advantages, including synergistic effects, cascaded reactions, and environmentally responsive selectivity. Nevertheless, along with these merits, the catalytic mechanism and rational design of multienzymic nanozymes are more complicated and elusive as compared to single-enzymic nanozymes. In this review, the multienzymic nanozymes classification scheme based on the numbers/types of activities, the internal and external factors regulating the multienzymatic activities, the rational design based on chemical, biomimetic, and computer-aided strategies, and recent progress in applications attributed to the advantages of multicatalytic activities are systematically discussed. Finally, current challenges and future perspectives regarding the development and application of multienzymatic nanozymes are suggested. This review aims to deepen the understanding and inspire the research in multienzymic nanozymes to a greater extent.

Organismal Function Enhancement through Biomaterial Intervention

Living organisms in nature, such as magnetotactic bacteria and eggs, generate various organic-inorganic hybrid materials, providing unique functionalities. Inspired by such natural hybrid materials, researchers can reasonably integrate biomaterials with living organisms either internally or externally to enhance their inherent capabilities and generate new functionalities. Currently, the approaches to enhancing organismal function through biomaterial intervention have undergone rapid development, progressing from the cellular level to the subcellular or multicellular level. In this review, we will concentrate on three key strategies related to biomaterial-guided bioenhancement, including biointerface engineering, artificial organelles, and 3D multicellular immune niches. For biointerface engineering, excess of amino acid residues on the surfaces of cells or viruses enables the assembly of materials to form versatile artificial shells, facilitating vaccine engineering and biological camouflage. Artificial organelles refer to artificial subcellular reactors made of biomaterials that persist in the cytoplasm, which imparts cells with on-demand regulatory ability. Moreover, macroscale biomaterials with spatiotemporal regulation characters enable the local recruitment and aggregation of cells, denoting multicellular niche to enhance crosstalk between cells and antigens. Collectively, harnessing the programmable chemical and biological attributes of biomaterials for organismal function enhancement shows significant potential in forthcoming biomedical applications.

Mn3O4 nanozymes prevent acetaminophen-induced acute liver injury by attenuating oxidative stress and countering inflammation

Acetaminophen (APAP) overdose is steadily becoming the chief reason for drug-induced acute liver failure, yet limited treatment is currently clinically available. Considering that the mechanism of APAP-induced hepatotoxicity is inseparable from oxidative stress and inflammation, a biocompatible Mn3O4 nanozyme mimicking superoxide dismutase (SOD) and catalase (CAT) activities and possessing reactive oxygen species (ROS)-scavenging capacity and antiapoptotic properties, is reported herein as a promising nanodrug to treat APAP-induced liver injury (AILI). Possessing bioactive enzyme-like functions, Mn3O4 nanoparticles (NPs) can not only reduce the oxidative stress on the liver by decreasing ROS accumulation but also downregulate the infiltration of inflammatory macrophages that secrete proinflammatory cytokines (tumor necrosis factor-α, interleukin-1β, and interleukin-6). Notably, the bifunctional Mn3O4 NPs mediate nuclear factor-erythroid 2 p45-related factor 2 signaling pathway activation and nuclear factor kappa B signaling pathway inhibition to effectively prevent the already fragile APAP-overdosed murine hepatocytes from being attacked again, thus mitigating hepatocyte apoptosis and alleviating APAP-induced liver damage. Thus, the Mn3O4 nanozyme (Mn3O4 NPs) evaluated in this study has potential preventive and therapeutic effects on AILI.

A Novel Endoplasmic Reticulum-Targeted Metal-Organic Framework-Confined Ruthenium (Ru) Nanozyme Regulation of Oxidative Stress for Central Post-Stroke Pain

Central post-stroke pain (CPSP) is a chronic neuropathic pain caused by cerebrovascular lesion or disfunction after stroke. Convincing evidence suggest that excessive reactive oxygen species (ROS), generated matrix metalloproteinase (MMPs) and neuroinflammation are largely involved in the development of pain. In this study, an effective strategy is reported for treating pain hypersensitivity using an endoplasmic reticulum (ER)-targeted metal-organic framework (MOF)-confined ruthenium (Ru) nanozyme. The Ru MOF is coated with a p-dodecylbenzene sulfonamide (p-DBSN) modified liposome with endoplasmic reticulum-targeted function. The experimental results reveals that ROS, Emmprin, MMP-2, and MMP-9 are upregulated in the brain of CPSP mice, along with the elevated expression of inflammation markers such as TNF-α and IL-6. Compared to vehicle, one-time intravenous administration of ER-Ru MOF significantly reduces mechanical hypersensitivity after CPSP for three days. Overall, ER-Ru MOF system can inhibit oxidative stress in the brain tissues of CPSP model, reduce MMPs expression, and suppress neuroinflammation response-induced injury, resulting in satisfactory prevention and effective treatment of CPSP during a hemorrhagic stroke. The ER-Ru MOF is expected to be useful for the treatment of neurological diseases associated with the vicious activation of ROS, based on the generality of the approach used in this study.

Endogenous stimuli-responsive drug delivery nanoplatforms for kidney disease therapy

Kidney disease is one of the most life-threatening health problems, affecting millions of people in the world. Commonly used steroids and immunosuppressants often fall exceptionally short of outcomes with inescapable systemic toxicity. With the booming research in nanobiotechnology, stimuli-responsive nanoplatform has come an appealing therapeutic strategy for kidney disease. Endogenous stimuli-responsive materials have shown profuse promise owing to their enhanced spatiotemporal control and precise to the location of the lesion. This review focuses on recent advances stimuli-responsive drug delivery nano-architectonics for kidney disease. First, a brief introduction of pathogenesis of kidney disease and pathological microenvironment were provided. Then, various endogenous stimulus involved in drug delivery nanoplatforms including pH, ROS, enzymes, and glucose were categorized based on the pathological mechanisms of kidney disease. Next, we separately summarized literature examples of endogenous stimuli-responsive nanomaterials, and outlined the design strategies and response mechanisms. Finally, the paper was concluded by discussing remaining challenges and future perspectives of endogenous stimuli-responsive drug delivery nanoplatform for expediting the speed of development and clinical applications.

Engineered nanodrug targeting oxidative stress for treatment of acute kidney injury

Acute kidney injury (AKI) is a clinical syndrome characterized by a rapid decline in renal function, and is associated with a high risk of death. Many pathological changes happen in the process of AKI, including crucial alterations to oxidative stress levels. Numerous efforts have thus been made to develop effective medicines to scavenge excess reactive oxygen species (ROS). However, researchers have encountered several significant challenges, including unspecific biodistribution, high biotoxicity, and in vivo instability. To address these problems, engineered nanoparticles have been developed to target oxidative stress and treat AKI. This review thoroughly discusses the methods that empower nanodrugs to specifically target the glomerular filtration barrier and presents the latest achievements in engineering novel ROS-scavenging nanodrugs in clustered sections. The analysis of each study's breakthroughs and imperfections visualizes the progress made in developing effective nanodrugs with specific biodistribution and oxidative stress-targeting capabilities. This review fills the blank of a comprehensive outline over current progress in applying nanotechnology to treat AKI, providing potential insights for further research.

Biomineralized RuO2 Nanozyme with Multi-Enzyme Activity for Ultrasound-Triggered Peroxynitrite-Boosted Ferroptosis

Ferroptosis, as a non-apoptotic cell death pathway, has attracted increasing attention for cancer therapy. However, the clinical application of ferroptosis-participated modalities is severely limited by the low efficiency owing to the intrinsic intracellular regulation pathways. Herein, chlorin e6 (Ce6) and N-acetyl-l-cysteine-conjugated bovine serum albumin-ruthenium dioxide is elaborately designed and constructed for ultrasound-triggered peroxynitrite-mediated ferroptosis. Upon ultrasound stimulation, the sonosensitizers of Ce6 and RuO2 exhibit highly efficient singlet oxygen (1 O2 ) generation capacity, which is sequentially amplified by superoxide dismutase and catalase-mimicking activity of RuO2 with hypoxia relief. Meanwhile, the S-nitrosothiol group in BCNR breaks off to release nitric oxide (NO) on-demand, which then reacts with 1 O2 forming highly cytotoxic peroxynitrite (ONOO- ) spontaneously. Importantly, BCNR nanozyme with glutathione peroxidase-mimicking activity can consume glutathione (GSH), along with the generated ONOO- downregulates glutathione reductase, avoiding GSH regeneration. The two-parallel approach ensures complete depletion of GSH within the tumor, resulting in the boosted ferroptosis sensitization of cancer cells. Thus, this work presents a superior paradigm for designing peroxynitrite-boosted ferroptosis sensitization cancer therapeutic.

Reactive X (where X = O, N, S, C, Cl, Br, and I) species nanomedicine

Reactive oxygen, nitrogen, sulfur, carbonyl, chlorine, bromine, and iodine species (RXS, where X = O, N, S, C, Cl, Br, and I) have important roles in various normal physiological processes and act as essential regulators of cell metabolism; their inherent biological activities govern cell signaling, immune balance, and tissue homeostasis. However, an imbalance between RXS production and consumption will induce the occurrence and development of various diseases. Due to the considerable progress of nanomedicine, a variety of nanosystems that can regulate RXS has been rationally designed and engineered for restoring RXS balance to halt the pathological processes of different diseases. The invention of radical-regulating nanomaterials creates the possibility of intriguing projects for disease treatment and promotes advances in nanomedicine. In this comprehensive review, we summarize, discuss, and highlight very-recent advances in RXS-based nanomedicine for versatile disease treatments. This review particularly focuses on the types and pathological effects of these reactive species and explores the biological effects of RXS-based nanomaterials, accompanied by a discussion and the outlook of the challenges faced and future clinical translations of RXS nanomedicines.

Self-assembled hemin-conjugated heparin with dual-enzymatic cascade reaction activities for acute kidney injury

Nanozymes have prominent catalytic activities with high stability as a substitute for unstable and expensive natural enzymes. However, most nanozymes are metal/inorganic nanomaterials, facing difficulty in clinical translation due to their unproven biosafety and limited biodegradability issues. Hemin, an organometallic porphyrin, was newly found to possess superoxide dismutase (SOD) mimetic activity along with previously known catalase (CAT) mimetic activity. However, hemin has poor bioavailability due to its low water solubility. Therefore, a highly biocompatible and biodegradable organic-based nanozyme system with SOD/CAT mimetic cascade reaction activity was developed by conjugating hemin to heparin (HepH) or chitosan (CS-H). Between them, Hep-H formed a smaller (<50 nm) and more stable self-assembled nanostructure and even possessed much higher and more stable SOD and CAT activities as well as the cascade reaction activity compared to CS-H and free hemin. Hep-H also showed a better cell protection effect against reactive oxygen species (ROS) compared to CS-H and hemin in vitro. Furthermore, Hep-H was selectively delivered to the injured kidney upon intravenous administration at the analysis time point (24 h) and exhibited excellent therapeutic effects on an acute kidney injury model by efficiently removing ROS, reducing inflammation, and minimizing structural and functional damage to the kidney.

Antioxidative 0-dimensional nanodrugs overcome obstacles in AKI antioxidant therapy

Acute kidney injury (AKI) is a commonly encountered syndrome associated with various aetiologies and pathophysiological processes leading to enormous health risks and economic losses. In the absence of specific drugs to treat AKI, hemodialysis remains the primary clinical treatment for AKI patients. The revelation of the pathology opens new horizons for antioxidant therapy in the treatment of AKI. However, small molecule antioxidant drugs and common nanozymes have failed to challenge AKI due to their unsatisfactory drug properties and renal physiological barriers. 0-Dimensional (0D) antioxidant nanodrugs stand out at this time thanks to their small size and high performance. Recently, a number of research studies have been carried out around 0D nanodrugs for alleviating AKI, and their multi-antioxidant enzyme mimetic activities, smooth glomerular filtration barrier permeability and excellent biocompatibility have been investigated. Here, we comprehensively summarize recent advances in 0D nanodrugs for AKI antioxidant therapy. We classify these representative studies into three categories according to the characteristics of 0D nanomaterials, namely ultra-small metal nanodots, inorganic non-metallic quantum dots and polymer nanodots. We focus on the antioxidant mechanisms and their distribution in vivo in each inspiring work, and the purpose and ingenuity of each design are rigorously captured and described. Finally, we provide our reflections and prospects for 0D antioxidant nanodrugs in AKI treatment. This mini review provides unique insights and valuable clues in the design of 0D nanodrugs and other kidney absorbable drugs.

Neutrophil Membrane-Inspired Nanorobots Act as Antioxidants Ameliorate Ischemia Reperfusion-Induced Acute Kidney Injury

Ischemia/reperfusion (I/R) injury causes excessive oxidative events and initiates destructive inflammatory responses, and it is an important promoter to the pathology of various pathema states. Ferroptosis is an iron-dependent type of nonapoptotic cell death accompanied by the accumulation of membrane lipid peroxide and consumption of polyunsaturated fatty acid, and it plays a key role in I/R injury diseases. Moreover, the excessive production of inflammatory cytokines contributes to the development of acute kidney injury. Here, we reported neutrophil membrane-coated copper-based nanoparticles (N-Cu5.4O@DFO NPs) for I/R kidney injury treatment. The highly biocompatible and stable N-Cu5.4O@DFO NPs showed excellent antioxidant and iron ion scavenging abilities in vitro. Our finding showed that the N-Cu5.4O@DFO NPs strategy could significantly accumulate in the inflammatory kidney, reduce oxidative damage events and inflammatory response, and finally achieve synergistic therapy against renal I/R injury. This work promotes the development of nanoantioxidant agents with multiple antioxidant properties for the therapy of other I/R injury diseases.

Biopolymer-Based Nanosystems: Potential Novel Carriers for Kidney Drug Delivery

Kidney disease has become a serious public health problem throughout the world, and its treatment and management constitute a huge global economic burden. Currently, the main clinical treatments are not sufficient to cure kidney diseases. During its development, nanotechnology has shown unprecedented potential for application to kidney diseases. However, nanotechnology has disadvantages such as high cost and poor bioavailability. In contrast, biopolymers are not only widely available but also highly bioavailable. Therefore, biopolymer-based nanosystems offer new promising solutions for the treatment of kidney diseases. This paper reviews the biopolymer-based nanosystems that have been used for renal diseases and describes strategies for the specific, targeted delivery of drugs to the kidney as well as the physicochemical properties of the nanoparticles that affect the targeting success.

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.

Nanodrugs alleviate acute kidney injury: Manipulate RONS at kidney

Currently, there are no clinical drugs available to treat acute kidney injury (AKI). Given the high prevalence and high mortality rate of AKI, the development of drugs to effectively treat AKI is a huge unmet medical need and a research hotspot. Although existing evidence fully demonstrates that reactive oxygen and nitrogen species (RONS) burst at the AKI site is a major contributor to AKI progression, the heterogeneity, complexity, and unique physiological structure of the kidney make most antioxidant and anti-inflammatory small molecule drugs ineffective because of the lack of kidney targeting and side effects. Recently, nanodrugs with intrinsic kidney targeting through the control of size, shape, and surface properties have opened exciting prospects for the treatment of AKI. Many antioxidant nanodrugs have emerged to address the limitations of current AKI treatments. In this review, we systematically summarized for the first time about the emerging nanodrugs that exploit the pathological and physiological features of the kidney to overcome the limitations of traditional small-molecule drugs to achieve high AKI efficacy. First, we analyzed the pathological structural characteristics of AKI and the main pathological mechanism of AKI: hypoxia, harmful substance accumulation-induced RONS burst at the renal site despite the multifactorial initiation and heterogeneity of AKI. Subsequently, we introduced the strategies used to improve renal targeting and reviewed advances of nanodrugs for AKI: nano-RONS-sacrificial agents, antioxidant nanozymes, and nanocarriers for antioxidants and anti-inflammatory drugs. These nanodrugs have demonstrated excellent therapeutic effects, such as greatly reducing oxidative stress damage, restoring renal function, and low side effects. Finally, we discussed the challenges and future directions for translating nanodrugs into clinical AKI treatment.

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AKI is a common clinical acute syndrome with high morbidity and mortality but without effective clinical drug available.

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Hypoxia and accumulation of toxic substances are key pathological features of various heterogeneous AKI.

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Excessive RONS is the core of the pathological mechanism of AKI.

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The development of nanodrugs is expected to achieve successful treatment in AKI.

Macrophage Polarization Induced by Bacteria-Responsive Antibiotic-Loaded Nanozymes for Multidrug Resistance-Bacterial Infections Management

Inherited bacterial resistance and biofilm-induced local immune inactivation are important factors in the failure of antibiotics to fight against bacterial infections. Herein, antibiotic-loaded mesoporous nanozymes (HA@MRuO₂ -Cip/GOx) are fabricated for overcoming bacterial resistance, and activating the local immunosuppression in biofilm microenvironment (BME). HA@MRuO₂ -Cip/GOx are prepared by physical adsorption between ciprofloxacin (Cip) or glucose oxidase (GOx) and MRuO₂ NPs, and modified with hyaluronic acid (HA). In vitro, HA@MRuO₂ -Cip/GOx cleaves extracellular DNA (eDNA) to disrupt biofilm, thereby enhancing Cip kill planktonic bacteria. Furthermore, HA@MRuO₂ -Cip/GOx can induce polarization and enhance phagocytosis of a macrophage-derived cell line. More importantly, in vivo therapeutic performance confirms that HA@MRuO₂ -Cip/GOx can trigger macrophage-related immunity, and effectively alleviate MRSA-bacterial lung infections. Accordingly, nanocatalytic therapy combined with targeted delivery of antibiotics could enhance the treatment of bacterial infections.

Glutathione peroxidase-like nanozymes: mechanism, classification, and bioapplication

The field of nanozymes is developing rapidly. In particular, glutathione peroxidase (GPx)-like nanozymes, which catalytically reduce H₂O₂/organic hydroperoxides to H₂O/alcohols, have attracted considerable attention. GPx-like nanozymes are powerful antioxidant enzymes known to combat oxidative stress. They have broad applications, including cytoprotection, anti-inflammation, neuroprotection, tumor therapy, and anti-aging. Although much progress has been made, GPx-like nanozymes have not been well discussed or fully reviewed as other nanozymes. This review aims to summarize recent advances on GPx-like nanozymes from the vantage point of mechanism, classification, and bioapplication. Future prospects for advancing their design and application are also discussed.

Maneuvering the Peroxidase-Like Activity of Palladium-Based Nanozymes by Alloying with Oxophilic Bismuth for Biosensing

Engineering the catalytic performance of nanozymes is of vital importance for their broad applications in biological analysis, cancer treatment, and environmental management. Herein, a strategy to boost the peroxidase-like activity of Pd-based nanozymes with oxophilic metallic bismuth (Bi) is demonstrated, which is based on the incorporation of oxophilic Bi in the Pd-based alloy nanocrystals (NCs). To synthesize PdBi alloy NCs, a seed-mediated method is employed with the assistance of underpotential deposition (UPD) of Bi on Pd. The strong interaction of Bi atoms with Pd surfaces favors the formation of alloy structures with controllable shapes and excellent monodispersity. More importantly, the PdBi NCs show excellent peroxidase-like activities compared with pristine Pd NCs. The structure-function correlations for the PdBi nanozymes are elucidated, and an indirect colorimetric method based on cascade reactions to determine alkaline phosphatase (ALP) is established. This method has good linear range, low detection limit, excellent selectivity, and anti-interference. Collectively, this work not only provides new insights for the design of high-efficiency nanozymes, expands the colorimetric sensing platform based on enzyme cascade reactions, but also represents a new example for UPD-directed synthesis of alloy NCs.

Self-assembled hyaluronic acid-coated nanocomplexes for targeted delivery of curcumin alleviate acute kidney injury

Acute kidney injury (AKI) is a pathological process with high morbidity, and drug resistance is easy to occur due to untargeted drug therapy. Curcumin can repair acute kidney injury. The expression of the CD44 receptor in renal tubular epithelial cells is abnormally elevated during AKI, and hyaluronic acid (HA) has the ability to bind specifically to the CD44 receptor. In this study, we developed a hyaluronic acid-coated liposome (HALP) nanocomplexes that targeted renal epithelial cells and its effect of relieving AKI was investigated. HALP was formed by self-assembly through the electrostatic interaction of curcumin-loaded cationic liposomes (LP) with hyaluronic acid and responds to the release of curcumin in the acidic microenvironment of lesions to treat AKI. HALP had good stability and biocompatibility. The in vitro results showed that compared to LP, HALP exhibited higher antioxidant, anti-inflammatory, and anti-apoptotic capacities. The AKI model suggested that HALP could not only target and accumulate in the injured kidney but also had an excellent ability to reduce the inflammatory response, which decreased tubular necrosis and restored kidney function.

Sustained intra-articular reactive oxygen species scavenging and alleviation of osteoarthritis by biocompatible amino-modified tantalum nanoparticles

Recent studies highlight the vital role of oxidative stress and reactive oxygen species (ROS) during progression of osteoarthritis (OA). Attenuating oxidative stress and reducing reactive oxygen species generation in joints represent reasonable strategies for the treatment of osteoarthritis. To address the potential question for clinical translation, and improve the biocompatibility and long-term performance of current antioxidants, the present study provided high biocompatible small positively charged tantalum nanoparticles (Ta-NH₂ NPs) with sustained intra-articular catalase activity and first applied to osteoarthritis intervention. Our in vitro results showed that Ta-NH₂ NPs were stable with good biocompatibility, and protected viability and hyaline-like phenotype in H₂O₂-challenged chondrocytes. In addition, the in vivo biodistribution data demonstrated a sustained retention of Ta-NH₂ NPs in the joint cavity, particularly in articular cartilage without organ toxicity and abnormality in hemogram or blood biochemistry indexes. Finally, compared with catalase (CAT), Ta-NH₂ NPs exhibited long-term therapeutic effect in monosodium iodoacetate (MIA) induced osteoarthritis model. This study preliminarily explored the potential of simply modified metal nanoparticles as effective reactive oxygen species scavenging agent for osteoarthritis intervention, and offered a novel strategy to achieve sustained reactive oxygen species suppression using biocompatible Ta-based nano-medicine in oxidative stress related diseases.

Recent Advances in ROS-Scavenging Metallic Nanozymes for Anti-Inflammatory Diseases: A Review

Oxidative stress and dysregulated inflammatory responses are the hallmarks of inflammatory disorders, which are key contributors to high mortality rates and impose a substantial economic burden on society. Reactive oxygen species (ROS) are vital signaling molecules that promote the development of inflammatory disorders. The existing mainstream therapeutic approaches, including steroid and non-steroidal anti-inflammatory drugs, and proinflammatory cytokine inhibitors with anti-leucocyte inhibitors, are not efficient at curing the adverse effects of severe inflammation. Moreover, they have serious side effects. Metallic nanozymes (MNZs) mimic the endogenous enzymatic process and are promising candidates for the treatment of ROS-associated inflammatory disorders. Owing to the existing level of development of these metallic nanozymes, they are efficient at scavenging excess ROS and can resolve the drawbacks of traditional therapies. This review summarizes the context of ROS during inflammation and provides an overview of recent advances in metallic nanozymes as therapeutic agents. Furthermore, the challenges associated with MNZs and an outline for future to promote the clinical translation of MNZs are discussed. Our review of this expanding multidisciplinary field will benefit the current research and clinical application of metallic-nanozyme-based ROS scavenging in inflammatory disease treatment.

Curcumin alleviated oxidation stress injury by mediating osteopontin in nephrolithiasis rats

PURPOSE

To explore the role and mechanism of curcumin (Cur) in reducing oxidative stress damage in rats with nephrolithiasis induced by ethylene glycol (EG).

METHODS

Thirty male rats were divided into normal control, model, positive (10% potassium citrate), Cur-10 (10 mg/kg curcumin) and Cur-20 (20 mg/kg curcumin) groups.

RESULTS

The results of kidney tissue section stained by hematoxylin-eosin and von Kossa showed that curcumin treatment can inhibit the formation of kidney stones. The biochemical test results showed that the urea (Ur), creatinine (Cr), uric acid (UA), inorganic phosphorus and Ca2+ concentrations in urine decreased after being treated with curcumin. There were significant differences between different doses of curcumin (P < 0.05). Compared with the Cur-10 group, Cur-20 had a more significant inhibitory effect on malondialdehyde (MDA) (P < 0.05). In addition, reverse transcription polymerase chain reaction (PCR) detection and immunohistochemical results indicated that the osteopontin (OPN) in the kidney was significantly reduced after curcumin treatment.

CONCLUSIONS

Curcumin could reduce the oxidative stress damage caused by EG-induced kidney stones.

Structure design mechanisms and inflammatory disease applications of nanozymes

Nanozymes are artificial enzymes with high catalytic activity, low cost, and good biocompatibility, and have received ever-increasing attention in recent years. Various inorganic and organic nanoparticles have been found to exhibit enzyme-like activities and are used as nanozymes for diverse biomedical applications ranging from tumor imaging and therapeutics to detection. However, their further clinical applications are hindered by the potential toxicity and long-term retention of nanomaterials in vivo. Clarifying the catalytic mechanism of nanozymes and identifying the key factors responsible for their behavior can guide the design of nanozyme structure, enlighten the ways to improve their enzyme-like activities, and minimize the dosage of nanozymes, leading to reduced toxicity to the human body for a real biomedical application prospect. In particular, inflammation occurring in numerous diseases is closely related to reactive oxygen species, and the active oxygen scavenging ability of nanozymes potentially exerts excellent therapeutic effects on inflammatory diseases. In this review, we systematically summarize the structure-activity relationship of nanozymes, including regulation strategies for size and morphology, surface structure, and composition. Based on the structure-activity mechanisms, a series of chemically designed nanozymes developed to target various inflammatory diseases are briefly summarized.

Low dimensional nanomaterials for treating acute kidney injury

Acute kidney injury (AKI) is one of the most common severe complications among hospitalized patients. In the absence of specific drugs to treat AKI, hemodialysis remains the primary clinical treatment for AKI patients. AKI treatment has received significant attention recently due to the excellent drug delivery capabilities of low-dimensional nanomaterials (LDNs) and their unique therapeutic effects. Diverse LDNs have been proposed to treat AKI, with promising results and the potential for future clinical application. This article aims to provide an overview of the pathogenesis of AKI and the recent advances in the treatment of AKI using different types of LDNs. In addition, it is intended to provide theoretical support for the design of LDNs and implications for AKI treatment.

Reactive Oxygen Species- and Cell-Free DNA-Scavenging Mn3O4 Nanozymes for Acute Kidney Injury Therapy

Reactive oxygen species (ROS) scavenging therapy toward acute kidney injury (AKI) is promising, but no effective ROS scavenging drug has been developed yet. Moreover, cell-free DNA (cfDNA) is also involved in AKI, but the corresponding therapies have not been well developed. To tackle these challenges, Mn₃O₄ nanoflowers (Nfs) possessing both ROS and cfDNA scavenging activities were developed for better AKI protection as follows. First, Mn₃O₄ Nfs could protect HK2 cells through cascade ROS scavenging (dismutating ^·O₂^- into H₂O₂ by superoxide dismutase-like activity and then decomposing H₂O₂ by catalase-like activity). Second, Mn₃O₄ Nfs could efficiently adsorb cfDNA and then decrease the inflammation caused by cfDNA. Combined, remarkable therapeutic efficacy was achieved in both cisplatin-induced and ischemia-reperfusion AKI murine models. Furthermore, Mn₃O₄ Nfs could be used for the T₁-MRI real-time imaging of AKI. This study not only offered a promising treatment for AKI but also showed the translational potential of nanozymes.

Novel gold-platinum nanoparticles serve as broad-spectrum antioxidants for attenuating ischemia reperfusion injury of the kidney

Kidney ischemia reperfusion injury (IRI) is a common and inevitable pathological condition in routine urological practices, especially during transplantation. Severe kidney IRI may even induce systemic damage to peripheral organs, and lead to multisystem organ failure. However, no standard clinical treatment option is currently available. It has been reported that kidney IRI is predominantly associated with abnormally increased endogenous reactive oxygen species (ROS). Scavenging excessive ROS may reduce the damage caused by oxidative stress and subsequently alleviate kidney IRI. Here, we reported a simple and efficient one-step synthesis of gold-platinum nanoparticles (AuPt NPs) with a gold core having a loose and branched outer platinum shell with superior ROS scavenging capacity to possibly treat kidney IRI. These AuPt NPs exhibited multiple enzyme-like anti-oxidative properties simultaneously possessing catalase- and peroxidase-like activity. These particles showed excellent cell protective capability, and alleviated kidney IRI both in vitro and in vivo without obvious toxicity, by suppressing cell apoptosis, inflammatory cytokine release, and inflammasome formation. Meanwhile, AuPt NPs also had an effect on inhibiting the transition to chronic kidney disease by reducing kidney fibrosis in the long term. Thus, AuPt NPs might be a good therapeutic agent for kidney IRI management and may be helpful for the development of clinical treatments for kidney IRI.

A platinum-ruthenium hybrid prodrug with multi-enzymatic activities for chemo-catalytic therapy of hypoxic tumors

Regulation of tumor hypoxia and redox homeostasis is a promising strategy for cancer therapy. Nanocatalytic medicine has played more and more important roles in this field because it can cleverly convert the efficiency and selectivity of catalysis into high therapeutic efficiency. Herein, we developed a platinum(iv)-ruthenium hybrid prodrug, named as Pt-Ru, for efficient chemo-catalytic synergistic therapy of hypoxic tumors. The ruthenium hybridization endowed the Pt(iv) prodrug with multi-enzyme catalytic activity, that is, mimicking catalase (CAT) to generate O2 in situ, mimicking peroxidase (POD) to produce reactive oxygen species, and mimicking glutathione peroxidase (GPx) to deplete GSH, thus effectively overcoming tumor hypoxia and cisplatin resistance. As a result, Pt-Ru treatment led to a superior anticancer efficacy to cisplatin both in vitro and in vivo. This work suggested redox homeostasis regulation as a tantalizing angle for developing the next generation of platinum drugs.

Co-delivery of celastrol and lutein with pH sensitive nano micelles for treating acute kidney injury

To treat acute kidney injury with high efficiency and low toxicity, a novel nanoplatform was developed to remove excess reactive oxygen species (ROS). Lutein (LU) and celastrol (Cel) were loaded into low molecular weight chitosan (CS) to prepare Cel@LU-CA-CS nanomicelles. Renal tubular epithelial (HK-2) cell uptake experiments showed that the drugs could be internalized in renal tubular via the megalin receptor. In this study, the amide bond formed by the reaction of citraconic anhydride (CA) with an amino group of CS could be destroyed under acidic conditions. Therefore, the drugs were released in HK-2 cells due to the acidic environment of the lysosome. In vitro studies showed that the nanomicelles could reduce toxicity in non-target organs and enhance therapeutic efficacy in acute kidney injury (AKI). In addition, Cel@LU-CA-CS micelles had alleviated kidney oxidative stress disorder and stabilized the mitochondrial membrane potential quickly. Next, in vivo studies proved that Cel@LU-CA-CS micelles could inhibit the activation of the NF-κB p65 and p38 MAPK inflammatory signaling pathways. Therefore, the micelles further reduced the overexpression of related inflammatory factors. In conclusion, Cel@LU-CA-CS nanomicelles could treat AKI with high efficiency and low toxicity, and inhibit renal fibrosis.

Nanozyme-Based Artificial Organelles: An Emerging Direction for Artificial Organelles

Artificial organelles are compartmentalized nanoreactors, in which enzymes or enzyme-mimic catalysts exhibit cascade catalytic activities to mimic the functions of natural organelles. Importantly, research on artificial organelles paves the way for the bottom-up design of synthetic cells. Due to the separation effect of microcompartments, the catalytic reactions of enzymes are performed without the influence of the surrounding medium. The current techniques for synthesizing artificial organelles rely on the strategies of encapsulating enzymes into vesicle-structured materials or reconstituting enzymes onto the microcompartment materials. However, there are still some problems including limited functions, unregulated activities, and difficulty in targeting delivery that hamper the applications of artificial organelles. The emergence of nanozymes (nanomaterials with enzyme-like activities) provides novel ideas for the fabrication of artificial organelles. Compared with natural enzymes, nanozymes are featured with multiple enzymatic activities, higher stability, easier to synthesize, lower cost, and excellent recyclability. Herein, the most recent advances in nanozyme-based artificial organelles are summarized. Moreover, the benefits of compartmental structures for the applications of nanozymes, as well as the functional requirements of microcompartment materials are also introduced. Finally, the potential applications of nanozyme-based artificial organelles in biomedicine and the related challenges are discussed.

Kidney functional stages influence the role of PEG end-group on the renal accumulation and distribution of PEGylated nanoparticles

Modification with polyethylene glycol (PEG), or PEGylation, has become a popular method to improve the efficiency of drug delivery in vivo using nanoparticle-based delivery systems. The PEG end-group plays an important role in the in vivo fate of PEGylated nanoparticles through its interactions with proteins in the serum and the cell membrane. However, the effects of PEG end-groups on the renal clearance of PEGylated nanoparticles remain unclear. Kidney function may also affect the renal accumulation and distribution of nanoparticles. Herein, we demonstrate that the accumulation and distribution of PEGylated nanoparticles in kidneys are significantly affected by both the PEG end-group and kidney function damage. Interestingly, compared to PEG with an amino or methoxy end-group, PEG with maleimide as the end-group markedly enhanced the accumulation of PEGylated nanoparticles in normal kidneys, which may improve renal clearance. However, obvious enhancements in the renal accumulation and medullary distribution of PEGylated nanoparticles are detected in kidneys with functional impairment. Damage to renal function further affects how the PEG end-group influences the accumulation and distribution of PEGylated nanoparticles in kidneys in vivo. Collectively, the findings provide deep insights into the interactions between PEGylated nanoparticles and kidneys in vivo.