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

Cerium Oxide Nanozymes Improve Skeletal Muscle Function in Gestational Diabetic Offspring by Attenuating Mitochondrial Oxidative Stress

Gestational diabetes mellitus (GDM) is a significant complication during pregnancy that results in abnormalities in the function of multiple systems in the offspring, which include skeletal muscle dysfunction and reduced systemic metabolic capacity. One of the primary causes behind this intergenerational effect is the presence of mitochondrial dysfunction and oxidative stress in the skeletal muscle of the offspring due to exposure to a high-glucose environment in utero. Cerium oxide (CeO2) nanozymes are antioxidant agents with polymerase activity that have been widely used in the treatment of inflammatory and aging diseases. In this study, we synthesized ultrasmall particle size CeO2 nanozymes and applied them in GDM mouse offspring. The CeO2 nanozymes demonstrated an ability to increase insulin sensitivity and enhance skeletal muscle motility in GDM offspring by improving mitochondrial activity, increasing mitochondrial ATP synthesis function, and restoring abnormal mitochondrial morphology. Furthermore, at the cellular level, CeO2 nanozymes could ameliorate metabolic dysregulation and decrease cell differentiation in adult muscle cells induced by hyperglycemic stimuli. This was achieved through the elimination of endogenous reactive oxygen species (ROS) and an improvement in mitochondrial oxidative respiration function. In conclusion, CeO2 nanozymes play a crucial role in preserving muscle function and maintaining the metabolic stability of organisms. Consequently, they serve to reverse the negative effects of GDM on skeletal muscle physiology in the offspring.

Nanozymes: Definition, Activity, and Mechanisms

"Nanozyme" is used to describe various catalysts from immobilized inorganic metal complexes, immobilized enzymes to inorganic nanoparticles. Here, the history of nanozymes is dvescribed in detail, and they can be largely separated into two types. Type 1 nanozymes refer to immobilized catalysts or enzymes on nanomaterials, which were dominant in the first decade since 2004. Type 2 nanozymes, which rely on the surface catalytic properties of inorganic nanomaterials, are the dominating type in the past decade. The definition of nanozymes is evolving, and a definition based on the same substrates and products as enzymes are able to cover most currently claimed nanozymes, although they may have different mechanisms compared to their enzyme counterparts. A broader definition can inspire application-based research to replace enzymes with nanomaterials for analytical, environmental, and biomedical applications. Comparison with enzymes also requires a clear definition of a nanozyme unit. Four ways of defining a nanozyme unit are described, with iron oxide and horseradish peroxidase activity comparison as examples in each definition. Growing work is devoted to understanding the catalytic mechanism of nanozymes, which provides a basis for further rational engineering of active sites. Finally, future perspective of the nanozyme field is discussed.

Nanozyme-Engineered Hydrogels for Anti-Inflammation and Skin Regeneration

Inflammatory skin disorders can cause chronic scarring and functional impairments, posing a significant burden on patients and the healthcare system. Conventional therapies, such as corticosteroids and nonsteroidal anti-inflammatory drugs, are limited in efficacy and associated with adverse effects. Recently, nanozyme (NZ)-based hydrogels have shown great promise in addressing these challenges. NZ-based hydrogels possess unique therapeutic abilities by combining the therapeutic benefits of redox nanomaterials with enzymatic activity and the water-retaining capacity of hydrogels. The multifaceted therapeutic effects of these hydrogels include scavenging reactive oxygen species and other inflammatory mediators modulating immune responses toward a pro-regenerative environment and enhancing regenerative potential by triggering cell migration and differentiation. This review highlights the current state of the art in NZ-engineered hydrogels (NZ@hydrogels) for anti-inflammatory and skin regeneration applications. It also discusses the underlying chemo-mechano-biological mechanisms behind their effectiveness. Additionally, the challenges and future directions in this ground, particularly their clinical translation, are addressed. The insights provided in this review can aid in the design and engineering of novel NZ-based hydrogels, offering new possibilities for targeted and personalized skin-care therapies.

Conservation of the enzyme-like activity and biocompatibility of CeO2 nanozymes in simulated body fluids

Cerium oxide nanozymes (CeO2NZs) are attracting vast attention due to their antioxidant and catalytic properties and mimic the activities of multiple endogenous enzymes. However, as is the case for nanomedicines in general, the success in showing their unique medical applications has not been matched by an understanding of their pharmacokinetics, which is delaying their implementation in clinical settings. Furthermore, the data of their modifications in body fluids and the impact on their activity are scarce. Herein, two types of widely used CeO2NZs, electrostatically stabilized and coated with a mesoporous silica shell, were exposed to simulated saliva and lung, gastric and intestinal fluids, and cell culture media. Their physicochemical modifications and bioactivity were tracked over time up to 15 days combining the data of different characterization techniques and biological assays. The results show that the biocompatibility and antioxidant activity are retained in all cases despite the different evolution behaviors in different fluids, including agglomeration. This work provides an experimental basis from a pharmacokinetic perspective that supports the therapeutic effectiveness of CeO2NZs observed in vivo for the treatment of many conditions related to chronic inflammation and cancer, and suggests that they can be safely administered through different portals of entry including intravenous injection, oral ingestion or inhalation.

The Integration of Nanomedicine with Traditional Chinese Medicine: Drug Delivery of Natural Products and Other Opportunities

The integration of progressive technologies such as nanomedicine with the use of natural products from traditional medicine (TM) provides a unique opportunity for the longed-for harmonization between traditional and modern medicine. Although several actions have been initiated decades ago, a disparity of reasons including some misunderstandings between each other limits the possibilities of a truly complementation. Herein, we analyze some common challenges between nanomedicine and traditional Chinese medicine (TCM). These challenges, if solved in a consensual way, can give a boost to such harmonization. Nanomedicine is a recently born technology, while TCM has been used by the Chinese people for thousands of years. However, for these disciplines, the regulation and standardization of many of the protocols, especially related to the toxicity and safety, regulatory aspects, and manufacturing procedures, are under discussion. Besides, both TCM and nanomedicine still need to achieve a wider social acceptance. Herein, we first briefly discuss the strengths and weaknesses of TCM. This analysis serves to focus afterward on the aspects where TCM and nanomedicine can mutually help to bridge the existing gaps between TCM and Western modern medicine. As discussed, many of these challenges can be applied to TM in general. Finally, recent successful cases in scientific literature that merge TCM and nanomedicine are reviewed as examples of the benefits of this harmonization.

Perspective insights into hydrogels and nanomaterials for ischemic stroke

Ischemic stroke (IS) is a neurological disorder prevalent worldwide with a high disability and mortality rate. In the clinic setting, tissue plasminogen activator (tPA) and thrombectomy could restore blood flow of the occlusion region and improve the outcomes of IS patients; however, these therapies are restricted by a narrow time window. Although several preclinical trials have revealed the molecular and cellular mechanisms underlying infarct lesions, the translatability of most findings is unsatisfactory, which contributes to the emergence of new biomaterials, such as hydrogels and nanomaterials, for the treatment of IS. Biomaterials function as structural scaffolds or are combined with other compounds to release therapeutic drugs. Biomaterial-mediated drug delivery approaches could optimize the therapeutic effects based on their brain-targeting property, biocompatibility, and functionality. This review summarizes the advances in biomaterials in the last several years, aiming to discuss the therapeutic potential of new biomaterials from the bench to bedside. The promising prospects of new biomaterials indicate the possibility of an organic combination between materialogy and medicine, which is a novel field under exploration.

Introducing Nanozymes: New Horizons in Periodontal and Dental Implant Care

The prevalence of periodontal and peri-implant diseases has been increasing worldwide and has gained a lot of attention. As multifunctional nanomaterials with enzyme-like activity, nanozymes have earned a place in the biomedical field. In periodontics and implantology, nanozymes have contributed greatly to research on maintaining periodontal health and improving implant success rates. To highlight this progress, we review nanozymes for antimicrobial therapy, anti-inflammatory therapy, tissue regeneration promotion, and synergistic effects in periodontal and peri-implant diseases. The future prospects of nanozymes in periodontology and implantology are also discussed along with challenges.

How Does Immunomodulatory Nanoceria Works? ROS and Immunometabolism

Dysregulation of the immune system is associated with an overproduction of metabolic reactive oxygen species (ROS) and consequent oxidative stress. By buffering excess ROS, cerium oxide (CeO₂) nanoparticles (NPs) (nanoceria) not only protect from oxidative stress consequence of inflammation but also modulate the immune response towards inflammation resolution. Immunomodulation is the modulation (regulatory adjustment) of the immune system. It has natural and human-induced forms, and it is part of immunotherapy, in which immune responses are induced, amplified, attenuated, or prevented according to therapeutic goals. For decades, it has been observed that immune cells transform from relative metabolic quiescence to a highly active metabolic state during activation(1). These changes in metabolism affect fate and function over a broad range of timescales and cell types, always correlated to metabolic changes closely associated with mitochondria number and morphology. The question is how to control the immunochemical potential, thereby regulating the immune response, by administering cellular power supply. In this regard, immune cells show different general catabolic modes relative to their activation status, linked to their specific functions (maintenance, scavenging, defense, resolution, and repair) that can be correlated to different ROS requirements and production. Properly formulated, nanoceria is highly soluble, safe, and potentially biodegradable, and it may overcome current antioxidant substances limitations and thus open a new era for human health management.

XJB-5-131 Is a Mild Uncoupler of Oxidative Phosphorylation

BACKGROUND

Mitochondria (MT) are energy "powerhouses" of the cell and the decline in their function from oxidative damage is strongly correlated in many diseases. To suppress oxygen damage, we have developed and applied XJB-5-131 as a targeted platform for neutralizing reactive oxygen species (ROS) directly in MT. Although the beneficial activity of XJB-5-131 is well documented, the mechanism of its protective effects is not yet fully understood.

OBJECTIVE

Here, we elucidate the mechanism of protection for XJB-5-131, a mitochondrial targeted antioxidant and electron scavenger.

METHODS

The Seahorse Flux Analyzer was used to probe the respiratory states of isolated mouse brain mitochondria treated with XJB-5-131 compared to controls.

RESULTS

Surprisingly, there is no direct impact of XJB-5-131 radical scavenger on the electron flow through the electron transport chain. Rather, XJB-5-131 is a mild uncoupler of oxidative phosphorylation. The nitroxide moiety in XJB-5-131 acts as a superoxide dismutase mimic, which both extracts or donates electrons during redox reactions. The electron scavenging activity of XJB-5-131 prevents the leakage of electrons and reduces formation of superoxide anion, thereby reducing ROS.

CONCLUSION

We show here that XJB-5-131 is a mild uncoupler of oxidative phosphorylation in MT. The mild uncoupling property of XJB-5-131 arises from its redox properties, which exert a protective effect by reducing ROS-induced damage without sacrificing energy production. Because mitochondrial decline is a common and central feature of toxicity, the favorable properties of XJB-5-131 are likely to be useful in treating Huntington's disease and a wide spectrum of neurodegenerative diseases for which oxidative damage is a key component. The mild uncoupling properties of XJB-5-131 suggest a valuable mechanism of action for the design of clinically effective antioxidants.