Exploring the activities of ruthenium nanomaterials as reactive oxygen species scavengers

Oxidative stress modulating nanomaterials and their biochemical roles in nanomedicine

Many pathological conditions are predominantly associated with oxidative stress, arising from reactive oxygen species (ROS); therefore, the modulation of redox activities has been a key strategy to restore normal tissue functions. Current approaches involve establishing a favorable cellular redox environment through the administration of therapeutic drugs and redox-active nanomaterials (RANs). In particular, RANs not only provide a stable and reliable means of therapeutic delivery but also possess the capacity to finely tune various interconnected components, including radicals, enzymes, proteins, transcription factors, and metabolites. Here, we discuss the roles that engineered RANs play in a spectrum of pathological conditions, such as cancer, neurodegenerative diseases, infections, and inflammation. We visualize the dual functions of RANs as both generator and scavenger of ROS, emphasizing their profound impact on diverse cellular functions. The focus of this review is solely on inorganic redox-active nanomaterials (inorganic RANs). Additionally, we deliberate on the challenges associated with current RANs-based approaches and propose potential research directions for their future 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.

Assessment of the Potential Health Risk of Gold Nanoparticles Used in Nanomedicine

Due to unique properties, nanoparticles (NPs) have become a preferred material in biomedicine. The benefits of their use are indisputable, but their safety and potential toxicity are becoming more and more important. Especially, excessive production of reactive oxygen species (ROS) induced by the strong oxidation potential of metal NPs could evoke adverse effects associated with damage to nucleic acids, proteins and lipids. Our study gives a view on the potential cytotoxicity of gold NPs (Au NPs) of different size from the perspective of the redox state of healthy (HEK 293 T) and cancer (A375 and A594) cell lines. These cells were incubated in the presence of two concentrations of Au NPs for 24 h or 72 h and total antioxidant capacity, 8-isoprostane, and protein carbonyl levels were determined. Furthermore, the activity of antioxidant enzymes such as superoxide dismutase, glutathione peroxidase, and catalase was detected in cell lysates. Our results compared to the results of other laboratories are very contradictory. The outcomes also differ between healthy and cancer cell lines. However, there are certainly changes in the activities of antioxidant enzymes, as well as the damage to biological molecules due to increased NP-induced oxidative stress. But the final decision of the effect of Au NPs on the oxidative state of selected cell lines requires further research.

Ultrasmall Ruthenium Nanoparticles with Boosted Antioxidant Activity Upregulate Regulatory T Cells for Highly Efficient Liver Injury Therapy

Nanozymes exhibiting antioxidant activity are beneficial for the treatment of oxidative stress-associated diseases. Ruthenium nanoparticles (RuNPs) with multiple enzyme-like activities have attracted growing attention, but the relatively low antioxidant enzyme-like activities hinder their practical biomedical applications. Here, a size regulation strategy is presented to significantly boost the antioxidant enzyme-like activities of RuNPs. It is found that as the size of RuNPs decreases to ≈2.0 nm (sRuNP), the surface-oxidized Ru atoms become dominant, thus possessing an unprecedentedly boosted antioxidant activity as compared to medium-sized (≈3.9 nm) or large-sized counterparts (≈5.9 nm) that are mainly composed of surface metallic Ru atoms. Notably, based on their antioxidant enzyme-like activities and ultrasmall size, sRuNP can not only sustainably ameliorate oxidative stress but also upregulate regulatory T cells in late-stage acetaminophen (APAP)-induced liver injury (ALI). Consequently, sRuNPs perform highly efficient therapeutic efficiency on ALI mice even when treated at 6 h after APAP intoxication. This strategy is insightful for tuning the catalytic performances of nanozymes for their extensive biomedical applications.

Graphene encapsuled Ru nanocrystal with highly-efficient peroxidase-like activity for glutathione detection at near-physiological pH

A novel nanozyme comprised of graphene encapsuled Ru nanocrystals (Ru@G) with effective and stable peroxidase-like activity prepared using a chemical vapor deposition (CVD) method was used for the detection of glutathione at near-physiological pH.

Antioxidant Nanotherapies for the Treatment of Inflammatory Diseases

Reactive oxygen species (ROS) are essential in regulating various physiological functions. However, overproduction of ROS is implicated in the pathogenesis of various inflammatory diseases. Antioxidant therapy has thus represented an effective strategy for the treatment of oxidative stress relevant inflammatory diseases. Conventional anti-oxidative agents showed limited in vivo effects owing to their non-specific distribution and low retention in disease sites. Over the past decades, significant achievements have been made in the development of antioxidant nanotherapies that exhibit multiple advantages such as excellent pharmacokinetics, stable anti-oxidative activity, and intrinsic ROS-scavenging properties. This review provides a comprehensive overview on recent advances in antioxidant nanotherapies, including ROS-scavenging inorganic nanoparticles, organic nanoparticles with intrinsic antioxidant activity, and drug-loaded anti-oxidant nanoparticles. We highlight the biomedical applications of antioxidant nanotherapies in the treatment of different inflammatory diseases, with an emphasis on inflammatory bowel disease, cardiovascular disease, and brain diseases. Current challenges and future perspectives to promote clinical translation of antioxidant nanotherapies are also briefly discussed.

Ferroxidase-like and antibacterial activity of PtCu alloy nanoparticles

Many metal nanoparticles are reported to have intrinsic enzyme-like activities and offer great potential in chemical and biomedical applications. In this study, PtCu alloy nanoparticles (NPs), synthesized through hydrothermal treatment of Cu²⁺ and Pt²⁺ in an aqueous solution, were evaluated for ferroxidase-like and antibacterial activity. Electron spin resonance (ESR) spectroscopy and colorimetric methods were used to demonstrate that PtCu NPs exhibited strong ferroxidase-like activity in a weakly acidic environment and that this activity was not affected by the presence of most other ions, except silver. Based on the color reaction of salicylic acid in the presence of Fe³⁺, we tested the ferroxidase-like activity of PtCu NPs to specifically detect Fe²⁺ in a solution of an oral iron supplement and compared these results with data acquired from atomic absorption spectroscopy and the phenanthroline colorimetric method. The results showed that the newly developed PtCu NPs detection method was equivalent to or better than the other two methods used for Fe²⁺ detection. The antibacterial experiments showed that PtCu NPs have strong antibacterial activity against Staphylococcus aureus and Escherichia coli. Herein, we demonstrate that the peroxidase-like activity of PtCu NPs can catalyze H₂O₂ and generate hydroxyl radicals, which may elucidate the antibacterial activity of the PtCu NPs against S. aureus and E. coli. These results showed that PtCu NPs exhibited both ferroxidase- and peroxidase-like activity and that they may serve as convenient and efficient NPs for the detection of Fe²⁺ and for antibacterial applications.

Intrinsic catalytic activity of rhodium nanoparticles with respect to reactive oxygen species scavenging: implication for diminishing cytotoxicity

Noble metal nanoparticles (NPs) and their hybrids have demonstrated a strong potential to mimic the catalytic activity of natural enzymes and diminish oxidative stress. There is a large space to explore the intrinsic catalytic activity of Rh NPs with respect to reactive oxygen species (ROS) scavenging. We found that Rh NPs can quench H₂O₂, ^•OH, O₂^•-, ¹O₂ and inhibit lipid peroxidation under physiological conditions. In vitro cell experiments proved that Rh NPs have great biocompatibility and protect cells from oxidative damage caused by H₂O₂. This study can provide important insights that could inform future biological applications.

Influences of simulated gastrointestinal environment on physicochemical properties of gold nanoparticles and their implications on intestinal epithelial permeability

Gold nanoparticles (Au NPs) hold great promise in food, industrial and biomedical applications due to their unique physicochemical properties. However, influences of the gastrointestinal tract (GIT), a likely route for Au NPs administration, on the physicochemical properties of Au NPs has been rarely evaluated. Here, we investigated the influence of GIT fluids on the physicochemical properties of Au NPs (5, 50, and 100 nm) and their implications on intestinal epithelial permeability in vitro. Au NPs aggregated in fasted gastric fluids and generated hydroxyl radicals in the presence of H₂O₂. Cell studies showed that GIT fluids incubation of Au NPs affected the cellular uptake of Au NPs but did not induce cytotoxicity or disturb the intestinal epithelial permeability.

A comprehensive screening shows that ergothioneine is the most abundant antioxidant in the wild macrofungus Phylloporia ribis Ryvarden

The polar and non-polar extracts from the authenticated wild mushroom Phylloporia ribis were separated by hydrophilic interaction liquid chromatography (HILIC) and by reverse phase (RP)-HPLC, respectively. A split valve separated the eluents into two fractions for free-radical scavenging analysis and for structural identification. Forty-six compounds showed scavenging activity of the stable-free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). The structures of 8 antioxidants (inosine, caffeic acid, ergothioneine, p-hydroxybenzoic acid, adenosine, 3,4-dihydroxybenzaldehyde, apigenin, and naringenin) are characterized by Mass Spectrometer. Among them, ergothioneine was the most abundant (>65%) and most active antioxidant in P. ribis.

ROS scavenging Mn3O4 nanozymes for in vivo anti-inflammation

Reactive oxygen species (ROS) scavenging Mn₃O₄ nanozymes effectively protected live mice from ROS-induced ear-inflammation in vivo.

Reactive oxygen species (ROS)-induced oxidative stress is linked to various diseases, including cardiovascular disease and cancer. Though highly efficient natural ROS scavenging enzymes have been evolved, they are sensitive to environmental conditions and hard to mass-produce. Therefore, enormous efforts have been devoted to developing artificial enzymes with ROS scavenging activities. Among them, ROS scavenging nanozymes have recently attracted great interest owing to their enhanced stability, multi-functionality, and tunable activity. It has been implicated that Mn-contained nanozymes would possess efficient ROS scavenging activities, however only a few such nanozymes have been reported. To fill this gap, herein we demonstrated that Mn₃O₄ nanoparticles (NPs) possessed multiple enzyme mimicking activities (i.e., superoxide dismutase and catalase mimicking activities as well as hydroxyl radical scavenging activity). The Mn₃O₄ nanozymes therefore significantly scavenged superoxide radical as well as hydrogen peroxide and hydroxyl radical. Moreover, they were not only more stable than the corresponding natural enzymes but also superior to CeO₂ nanozymes in terms of ROS elimination. We showed that the Mn₃O₄ NPs not only exhibited excellent ROS removal efficacy in vitro but also effectively protected live mice from ROS-induced ear-inflammation in vivo. These results indicated that Mn₃O₄ nanozymes are promising therapeutic nanomedicine for treating ROS-related diseases.

Mimicking horseradish peroxidase and oxidase using ruthenium nanomaterials

Ru NPs could catalyze the oxidation of 3,3,5,5-tetramethylbenzidine, o-phenylenediamine and dopamine hydrochloride in the presence of H₂O₂, and also catalyze the oxidization of 3,3,5,5-tetramethylbenzidine and sodium l-ascorbate by dissolved oxygen.