Biogenic magnetic nanoparticles from Burkholderia sp. YN01 exhibiting intrinsic peroxidase-like activity and their applications

Unveiling the role of inorganic nanoparticles in Earth's biochemical evolution through electron transfer dynamics

This article explores the intricate interplay between inorganic nanoparticles and Earth's biochemical history, with a focus on their electron transfer properties. It reveals how iron oxide and sulfide nanoparticles, as examples of inorganic nanoparticles, exhibit oxidoreductase activity similar to proteins. Termed "life fossil oxidoreductases," these inorganic enzymes influence redox reactions, detoxification processes, and nutrient cycling in early Earth environments. By emphasizing the structural configuration of nanoparticles and their electron conformation, including oxygen defects and metal vacancies, especially electron hopping, the article provides a foundation for understanding inorganic enzyme mechanisms. This approach, rooted in physics, underscores that life's origin and evolution are governed by electron transfer principles within the framework of chemical equilibrium. Today, these nanoparticles serve as vital biocatalysts in natural ecosystems, participating in critical reactions for ecosystem health. The research highlights their enduring impact on Earth's history, shaping ecosystems and interacting with protein metal centers through shared electron transfer dynamics, offering insights into early life processes and adaptations.

Inorganic Fe-O and Fe-S oxidoreductases: paradigms for prebiotic chemistry and the evolution of enzymatic activity in biology

Oxidoreductases play crucial roles in electron transfer during biological redox reactions. These reactions are not exclusive to protein-based biocatalysts; nano-size (<100 nm), fine-grained inorganic colloids, such as iron oxides and sulfides, also participate. These nanocolloids exhibit intrinsic redox activity and possess direct electron transfer capacities comparable to their biological counterparts. The unique metal ion architecture of these nanocolloids, including electron configurations, coordination environment, electron conductivity, and the ability to promote spontaneous electron hopping, contributes to their transfer capabilities. Nano-size inorganic colloids are believed to be among the earliest 'oxidoreductases' to have 'evolved' on early Earth, playing critical roles in biological systems. Representing a distinct type of biocatalysts alongside metalloproteins, these nanoparticles offer an early alternative to protein-based oxidoreductase activity. While the roles of inorganic nano-sized catalysts in current Earth ecosystems are intuitively significant, they remain poorly understood and underestimated. Their contribution to chemical reactions and biogeochemical cycles likely helped shape and maintain the balance of our planet's ecosystems. However, their potential applications in biomedical, agricultural, and environmental protection sectors have not been fully explored or exploited. This review examines the structure, properties, and mechanisms of such catalysts from a material's evolutionary standpoint, aiming to raise awareness of their potential to provide innovative solutions to some of Earth's sustainability challenges.

PEG mediated NiMn2O4 nanomaterials as a nano catalyst for peroxidase mimetic activity and photocatalytic degradation

Artificial peroxidases have garnered a lot of attention owing to their tremendous superiority over their natural counterparts. Here, NiMn2O4 nanoparticles have been successfully prepared through PEG assisted hydrothermal method. The varied PEG concentrations significantly altered the morphology and particle size of the synthesizedmaterials. We demonstrate the improved peroxide-like assay of different NiMn2O4 nanoparticles for the first time. Among them, Ni4 nanoparticles exhibit good peroxidase-like activity by generating the oxidation of chromogenic substrate 3, 3', 5, 5'-tetramethylbenzidine (TMB) in the presence of H2O2 and a blue color charge transfer product with an absorption maximum is positioned at 652 nm. These observations led to the development of a method for assessingH2O2 that can be read visually and photometrically. The Ni4 nanoparticles show enhanced kinetics compared to the natural enzyme horse radish peroxidase (HRP) with a lower Km (0.168 mM) value. Additionally, this Ni4 nanosphere applies as a visible light photocatalyst for the degradation of methylene blue (MB) and rhodamine B (Rh B) dyes under visible-light irradiation. Under optimized conditions, the degradationrates of MB and Rh B are 68 and 80.7 %, respectively, after 210 min, and recyclable efficiency is about 99 % for Rh B photocatalytic degradation in the first test and 98 % for five cycles, and about 98 % for MB photocatalytic degradation in the first test and 97 % for five cycles.

Fe3 O4 nanozyme coating enhances light-driven biohydrogen production in self-photosensitized Shewanella oneidensis-CdS hybrid systems

Solar-driven biohybrid systems that produce chemical energy are a valuable objective in ongoing research. However, reactive oxygen species (ROS) that accompany nanoparticle production under light radiation severely affect the efficiency of biohybrid systems. In this study, we successfully constructed a two-hybrid system, Shewanella oneidensis-CdS and S. oneidensis-CdS@Fe3 O4 , in a simple, economical, and gentle manner. With the Fe3 O4 coating, ROS were considerably eliminated; the hydroxyl radical, superoxide radical, and hydrogen peroxide contents were reduced by 66.7%, 65.4%, and 72%, respectively, during light-driven S. oneidensis-CdS hydrogen production. S. oneidensis-CdS@Fe3 O4 showed a 2.6-fold higher hydrogen production (70 h) than S. oneidensis-CdS. Moreover, the S. oneidensis-CdS system produced an additional 367.8 μmol g-dcw-1 (70 h) of hydrogen compared with S. oneidensis during irradiation. The apparent quantum efficiencies of S. oneidensis-CdS and S. oneidensis-CdS@Fe3 O4 were 6.2% and 11.5%, respectively, exceeding values previously reported. In conclusion, a stable nanozyme coating effectively inhibited the cytotoxicity of CdS nanoparticles, providing an excellent production environment for bacteria. This study provides a rational strategy for protecting biohybrid systems from ROS toxicity and contributes to more efficient solar energy conversion in the future.

What are the inorganic nanozymes? Artificial or inorganic enzymes!

The research on inorganic nanozymes remains very active since the first paper on the “intrinsic peroxidase-like properties of ferromagnetic nanoparticles” was published in Nature Nanotechnology in 2007. However, there is...

Fe-N-C single-atom nanozymes with peroxidase-like activity for the detection of alkaline phosphatase

Single-atom nanozymes have drawn wide attention in bio-sensing for their remarkable merits such as low cost, high stability, and maximum atom utilization. Herein, a colorimetric strategy based on Fe-N-C single-atom nanozymes (Fe/NC-SAs) was established for the detection of alkaline phosphatase (ALP) activity. The Fe/NC-SAs prepared by pyrolysis have excellent peroxidase-like activity and can oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to a blue color product in the presence of hydrogen peroxide (H₂O₂). When ascorbic acid (AA) is added to the system, the blue color fades, and the absorbance has a linear relationship with the concentration of AA. Alkaline phosphatase (ALP) can catalyze the hydrolysis of ascorbic acid 2-phosphate (AAP) to produce AA. Thus, a strategy based on Fe/NC-SAs for the detection of ALP activity was established, which provided a linear range of 0.1-1.5 U L^-1 and a limit of detection as low as 0.05 U L^-1. Besides, Fe/NC-SAs showed high stability under harsh conditions. Moreover, an Fe/NC-SA-based assay was successfully validated using human serum samples for ALP determination with satisfactory results, and has broad prospects in the field of biosensing.

De Novo Iron Oxide Hydroxide, Ferrihydrite Produced by Comamonas testosteroni Exhibiting Intrinsic Peroxidase-Like Activity and Their Analytical Applications

Natural enzyme mimics have attracted considerable attention due to leakage of enzymes and their easy denaturation during their storage and immobilization procedure. Here in this study, for the first time, a new iron oxide hydroxide, ferrihydrite - Fe_1.44O_0.32 (OH) _3.68 magnetic nanoparticles were synthesized by bacterial strain named Comamonas testosteroni. The characterization of the produced magnetic nanoparticles was confirmed by transmission electron microscopy (TEM), Fourier-transform spectroscopy (FTIR), X-ray diffraction (XRD), and magnetization hysteresis loops. Further, these extracted nanoparticles were proven to have biogenic magnetic behavior and to exhibit enhanced peroxidase-like activity. It is capable of catalyzing the oxidation of 3, 3', 5, 5'-Tetramethylbenzidine (TMB) by H₂O₂ to produce blue color (typical color reactions). Catalysis was examined to follow Michaelis-Menton kinetics and the good affinity to both H₂O₂ and TMB. The K _m value of the Fe_1.44O_0.32 (OH) _3.68 with H₂O₂ and TMB as the substrate was 0.0775 and 0.0155 mM, respectively, which were lower than that of the natural enzyme (HRP). Experiments of electron spin resonance (ESR) spectroscopy proved that the BMNPs could catalyze H₂O₂ to produce hydroxyl radicals. As a new peroxidase mimetic, the BMNPs were exhibited to offer a simple, sensitive, and selective colorimetric method for determination of H₂O₂ and glucose and efficiently catalyze the detection of glucose in real blood samples.

Bacterial intracellular nanoparticles exhibiting antioxidant properties and the significance of their formation in ROS detoxification

Biogenic magnetic nanoparticles (BMNPs) can be formed by numerous microorganisms. However, the significance of their formation and their possible functions have not been explored in detail. To explore a possible function of Fe₃ O₄ NPs in Burkholderia sp. strain YN01, we investigated their catalytic abilities in the elimination of intracellular reactive oxygen species (ROS). Changes in ROS content under different conditions were assessed and showed that low oxygen and high iron concentrations in the growth medium promoted ROS production. However, the levels of ROS gradually decreased with BMNP formation, suggesting that these particles possess intrinsic superoxide dismutase (SOD)-like activity and catalase (CAT)-like activity, as proven in this study. To ensure that the observed ROS decrease was not due to antioxidase overexpression caused by the oxidative stress response, SOD and CAT were inhibited in vivo to analyse the ROS variation and BMNP yield under microoxic and high-iron conditions respectively. The results demonstrated that the formation of these intracellular iron nanoparticles was required for the efficient scavenging of excess ROS, which was dependent on their antioxidase-like properties. This result reveals a novel physiological function of biogenic intracellular Fe₃ O₄ nanoparticles.

Magnetosomes: biogenic iron nanoparticles produced by environmental bacteria

The scientific community's interest in magnetotactic bacteria has increased substantially in recent decades. These prokaryotes have the particularity of synthesizing nanomagnets, called magnetosomes. The majority of research is based on several scientific questions. Where do magnetotactic bacteria live, what are their characteristics, and why are they magnetic? What are the molecular phenomena of magnetosome biomineralization and what are the physical characteristics of magnetosomes? In addition to scientific curiosity to better understand these stunning organisms, there are biotechnological opportunities to consider. Magnetotactic bacteria, as well as magnetosomes, are used in medical applications, for example cancer treatment, or in environmental ones, for example bioremediation. In this mini-review, we investigated all the aspects mentioned above and summarized the currently available knowledge.

Nanomaterials with enzyme-like characteristics (nanozymes): next-generation artificial enzymes (II)

An updated comprehensive review to help researchers understand nanozymes better and in turn to advance the field.

Multifunctional nanozymes: enzyme-like catalytic activity combined with magnetism and surface plasmon resonance

Over decades, as alternatives to natural enzymes, highly-stable and low-cost artificial enzymes have been widely explored for various applications. In the field of artificial enzymes, functional nanomaterials with enzyme-like characteristics, termed as nanozymes, are currently attracting immense attention. Significant progress has been made in nanozyme research due to the exquisite control and impressive development of nanomaterials. Since nanozymes are endowed with unique properties from nanomaterials, an interesting investigation is multifunctionality, which opens up new potential applications for biomedical sensing and sustainable chemistry due to the combination of two or more distinct functions of high-performance nanozymes. To highlight the progress, in this review, we discuss two representative types of multifunctional nanozymes, including iron oxide nanomaterials with magnetic properties and metal nanomaterials with surface plasmon resonance. The applications are also covered to show the great promise of such multifunctional nanozymes. Future challenges and prospects are discussed at the end of this review.

Synthesis of Porous CoFe₂O₄ and Its Application as a Peroxidase Mimetic for Colorimetric Detection of H₂O₂ and Organic Pollutant Degradation

Porous CoFe₂O₄ was prepared via a simple and controllable method to develop a low-cost, high-efficiency, and good-stability nanozyme. The morphology and microstructure of the obtained CoFe₂O₄ was investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), specific surface area and pore analysis, and Raman spectroscopy. The results show that the annealing temperature has an important effect on the crystallinity, grain size, and specific surface area of CoFe₂O₄. CoFe₂O₄ obtained at 300 &deg;C (CF300) exhibits the largest surface area (up to 204.1 m² g^&minus;1) and the smallest grain size. The peroxidase-like activity of CoFe₂O₄ was further verified based on the oxidation of peroxidase substrate 3,3&rsquo;,5,5&rsquo;-tetramethylbenzidine (TMB) in the presence of H₂O₂. The best peroxidase-like activity for CF300 should be ascribed to its largest surface area and smallest grain size. On this basis, an effective method of colorimetric detection H₂O₂ was established. In addition, the porous CoFe₂O₄ was also used for the catalytic oxidation of methylene blue (MB), indicating potential applications in pollutant removal and water treatment.

Hydrolysis of Phosphate Esters Catalyzed by Inorganic Iron Oxide Nanoparticles Acting as Biocatalysts

Phosphorus ester hydrolysis is one of the key chemical processes in biological systems, including signaling, free-energy transaction, protein synthesis, and maintaining the integrity of genetic material. Hydrolysis of this otherwise kinetically stable phosphoester and/or phosphoanhydride bond is induced by enzymes such as purple acid phosphatase. Here, I report that, as in previously reported aged inorganic iron ion solutions, the iron oxide nanoparticles in the solution, which are trapped in a dialysis membrane tube filled with the various iron oxides, significantly promote the hydrolysis of the various phosphate esters, including the inorganic polyphosphates, with enzyme-like kinetics. This observation, along with those of recent studies of iron oxide, vanadium pentoxide, and molybdenum trioxide nanoparticles that behave as mimics of peroxidase, bromoperoxidase, and sulfite oxidase, respectively, indicates that the oxo-metal bond in the oxide nanoparticles is critical for the function of these corresponding natural metalloproteins. These inorganic biocatalysts challenge the traditional concept of replicator-first scenarios and support the metabolism-first hypothesis. As biocatalysts, these inorganic nanoparticles with enzyme-like activity may work in natural terrestrial environments and likely were at work in early Earth environments as well. They may have played an important role in the C, H, O, S, and P metabolic pathway with regard to the emergence and early evolution of life. Key Words: Enzyme-Hydrolysis-Iron oxide-Nanoparticles-Origin of life-Phosphate ester. Astrobiology 18, 294-310.

Iron Oxide Nanozyme: A Multifunctional Enzyme Mimetic for Biomedical Applications

Iron oxide nanoparticles have been widely used in many important fields due to their excellent nanoscale physical properties, such as magnetism/superparamagnetism. They are usually assumed to be biologically inert in biomedical applications. However, iron oxide nanoparticles were recently found to also possess intrinsic enzyme-like activities, and are now regarded as novel enzyme mimetics. A special term, "Nanozyme", has thus been coined to highlight the intrinsic enzymatic properties of such nanomaterials. Since then, iron oxide nanoparticles have been used as nanozymes to facilitate biomedical applications. In this review, we will introduce the enzymatic features of iron oxide nanozyme (IONzyme), and summarize its novel applications in biomedicine.

Nanozymes in bionanotechnology: from sensing to therapeutics and beyond

Nanozymes are nanomaterials with enzyme-like characteristics, which have found broad applications in various areas including bionanotechnology and beyond.