Dietary Iron Oxide Nanoparticles Delay Aging and Ameliorate Neurodegeneration in Drosophila

Synergistic Oxygen Generation and Reactive Oxygen Species Scavenging by Manganese Ferrite/Ceria Co-decorated Nanoparticles for Rheumatoid Arthritis Treatment

Poor O₂ supply to the infiltrated immune cells in the joint synovium of rheumatoid arthritis (RA) up-regulates hypoxia-inducible factor (HIF-1α) expression and induces reactive oxygen species (ROS) generation, both of which exacerbate synovial inflammation. Synovial inflammation in RA can be resolved by eliminating pro-inflammatory M1 macrophages and inducing anti-inflammatory M2 macrophages. Because hypoxia and ROS in the RA synovium play a crucial role in the induction of M1 macrophages and reduction of M2 macrophages, herein, we develop manganese ferrite and ceria nanoparticle-anchored mesoporous silica nanoparticles (MFC-MSNs) that can synergistically scavenge ROS and produce O₂ for reducing M1 macrophage levels and inducing M2 macrophages for RA treatment. MFC-MSNs exhibit a synergistic effect on O₂ generation and ROS scavenging that is attributed to the complementary reaction of ceria nanoparticles (NPs) that can scavenge intermediate hydroxyl radicals generated by manganese ferrite NPs in the process of O₂ generation during the Fenton reaction, leading to the efficient polarization of M1 to M2 macrophages both in vitro and in vivo. Intra-articular administration of MFC-MSNs to rat RA models alleviated hypoxia, inflammation, and pathological features in the joint. Furthermore, MSNs were used as a drug-delivery vehicle, releasing the anti-rheumatic drug methotrexate in a sustained manner to augment the therapeutic effect of MFC-MSNs. This study highlights the therapeutic potential of MFC-MSNs that simultaneously generate O₂ and scavenge ROS, subsequently driving inflammatory macrophages to the anti-inflammatory subtype for RA treatment.

Nanozymes: Classification, Catalytic Mechanisms, Activity Regulation, and Applications

Because of the high catalytic activities and substrate specificity, natural enzymes have been widely used in industrial, medical, and biological fields, etc. Although promising, they often suffer from intrinsic shortcomings such as high cost, low operational stability, and difficulties of recycling. To overcome these shortcomings, researchers have been devoted to the exploration of artificial enzyme mimics for a long time. Since the discovery of ferromagnetic nanoparticles with intrinsic horseradish peroxidase-like activity in 2007, a large amount of studies on nanozymes have been constantly emerging in the next decade. Nanozymes are one kind of nanomaterials with enzymatic catalytic properties. Compared with natural enzymes, nanozymes have the advantages such as low cost, high stability and durability, which have been widely used in industrial, medical, and biological fields. A thorough understanding of the possible catalytic mechanisms will contribute to the development of novel and high-efficient nanozymes, and the rational regulations of the activities of nanozymes are of great significance. In this review, we systematically introduce the classification, catalytic mechanism, activity regulation as well as recent research progress of nanozymes in the field of biosensing, environmental protection, and disease treatments, etc. in the past years. We also propose the current challenges of nanozymes as well as their future research focus. We anticipate this review may be of significance for the field to understand the properties of nanozymes and the development of novel nanomaterials with enzyme mimicking activities.

Cu (II)-based metal-organic xerogels as a novel nanozyme for colorimetric detection of dopamine

Cu (II)-based metal-organic gels (Cu-MOGs), which are formed by 4-[2,2':6',2″-terpyridine]-4'-ylbenzoic acid (Hcptpy) and Cu (II) through ionic interactions, π-π stacking, van der Waals and hydrogen bonding, have been simply synthesized and used for the preparation of Cu (II)-based metal-organic xerogels (Cu-MOXs). Owing to the metal active sites in Cu-MOXs, Cu-MOXs were successfully applied to chromogenic experiment. The peroxidase substrate 3,3',5,5'-tetramethylbenzidine (TMB), which could be catalyzed by Cu-MOXs from TMB to the oxidation state of TMB (oxTMB) and the color of TMB could be changed from colorless to blue with maximum absorbance at 657 nm, was selected as chromogenic agent. Thus, the Cu-MOXs-TMB-H₂O₂ system based on MOXs was established. Due to the inhibitory effect of dopamine (DA) on oxidation process of TMB, the characteristic absorption peak intensity of oxTMB decreased when the DA was added into the mixed solution. Subsequently, the Cu-MOXs-TMB- H₂O₂ system was used for DA detection. The linear range for DA was 0.5 μM-20 μM and the detection limit was 85.76 nM. Our work has helped to develop the promising application of Cu-MOGs material in the field of nanozymes property.

Modulating cell culture oxidative stress reduces protein glycation and acidic charge variant formation

Controlling acidic charge variants is critical for an industrial bioprocess due to the potential impact on therapeutic efficacy and safety. Achieving a consistent charge variant profile at manufacturing scale remains challenging and may require substantial resources to investigate effective control strategies. This is partially due to incomplete understanding of the underlying causes for charge variant formation during the cell culture process. To address this gap, we examined the effects of four process input factors (temperature, iron concentration, feed media age, and antioxidant (rosmarinic acid) concentration) on charge variant profile. These factors were found to affect the charge profile by modulating the cell culture oxidative state. Process conditions with higher acidic peaks corresponded to elevated supernatant peroxide concentration, intracellular reactive oxygen species (ROS) levels, or both. Changes in glycation level were the primary cause of the charge heterogeneity, and for the first time, supernatant peroxide was found to positively correlate with glycation levels. Based on these findings, a novel mathematical model was developed to demonstrate that the rate of acidic species formation was exponentially proportional to the concentrations of supernatant peroxide and protein product. This work provides critical insights into charge variant formation during the cell culture process and highlights the importance of modulating of cell culture oxidative stress for charge variant control.

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.

Age-associated decline in Nrf2 signaling and associated mtDNA damage may be involved in the degeneration of the auditory cortex: Implications for central presbycusis

Central presbycusis is the most common sensory disorder in the elderly population, however, the underlying molecular mechanism remains unclear. NF‑E2‑related factor 2 (Nrf2) is a key transcription factor in the cellular response to oxidative stress, however, the role of Nrf2 in central presbycusis remains to be elucidated. The aim of the present study was to investigate the pathogenesis of central presbycusis using a mimetic aging model induced by D‑galactose (D‑gal) in vivo and in vitro. The degeneration of the cell was determined with transmission electron microscopy, terminal deoxynucleotidyl transferase‑mediated deoxyuridine 5'‑triphosphate nick‑end labeling staining, and senescence‑associated β‑galactosidase staining. The expression of protein was detected by western blotting and immunofluorescence. The quantification of the mitochondrial DNA (mtDNA) 4,834‑base pair (bp) deletion and mRNA was detected by TaqMan quantitative polymerase chain reaction (qPCR) and reverse transcription‑qPCR respectively. Cell apoptosis and intracellular ROS in vitro were determined with flow cytometry. The levels of nuclear Nrf2, and the mRNA levels of Nrf2‑regulated antioxidant genes, were downregulated in the auditory cortex of aging rats, which was accompanied by an increase in 8‑hydroxy‑2'‑deoxyguanosine formation, an accumulation of mtDNA 4,834‑bp deletion, and neuron degeneration. In addition, oltipraz, a typical Nrf2 activator, was found to protect cells against D‑gal‑induced mtDNA damage and mitochondrial dysfunction by activating Nrf2 target genes in vitro. It was also observed that activating Nrf2 with oltipraz inhibited cell apoptosis and delayed senescence. Taken together, the data of the present study suggested that the age‑associated decline in Nrf2 signaling activity and the associated mtDNA damage in the auditory cortex may be implicated in the degeneration of the auditory cortex. Therefore, the restoration of Nrf2 signaling activity may represent a potential therapeutic strategy for central presbycusis.

Polydopamine Nanoparticles as Efficient Scavengers for Reactive Oxygen Species in Periodontal Disease

Antioxidative therapy has been considered an efficient strategy for the treatment of a series of excessive reactive oxygen species (ROS)-triggered diseases, including oxidative-stress-induced periodontal disease. However, current natural enzymes and nanozymes often show their high specificity toward given ROS and have insufficient antioxidative effects against multiple ROS generated in the diseases process. Meanwhile, multienzyme-based antioxidant defense systems are usually confined by the complicated synthesis as well as potential unwanted residue and toxicity. Various supports are highly needed to immobilize natural enzymes and antioxidants during the biorelated usages due to their low operational stability and difficulty of reuse. To overcome these limitations, we develop a high-performance platform by using biodegradable polydopamine nanoparticles (PDA NPs) as smart ROS scavengers in oxidative stress-induced periodontal disease. Although PDA-based materials are well-known to eliminate ROS both in vitro and in vivo, their antioxidative performance in periodontal disease and relative mechanisms have yet to be well-explored. In this study, PDA NPs can act as ROS scavengers in dental specialties with ideal outcomes. Spectroscopic and in vitro experiments provide strong evidence for the roles of PDA NPs in scavenging multiple ROS and suppressing ROS-induced inflammation reactions. In addition to the above investigations, the results from a murine periodontitis model clearly demonstrate the feasibility of PDA NPs as robust antioxidants with which to remove ROS and decrease periodontal inflammation without any side effects. Taken together, the results from our present study will provide valuable insight into the development of safe and efficient antioxidant defense platforms for further biomedical uses.

Biomimetic nanoflowers by self-assembly of nanozymes to induce intracellular oxidative damage against hypoxic tumors

Reactive oxygen species (ROS)-induced apoptosis is a promising treatment strategy for malignant neoplasms. However, current systems are highly dependent on oxygen status and/or external stimuli to generate ROS, which greatly limit their therapeutic efficacy particularly in hypoxic tumors. Herein, we develop a biomimetic nanoflower based on self-assembly of nanozymes that can catalyze a cascade of intracellular biochemical reactions to produce ROS in both normoxic and hypoxic conditions without any external stimuli. In our formulation, PtCo nanoparticles are firstly synthesized and used to direct the growth of MnO2. By adjusting the ratio of reactants, highly-ordered MnO2@PtCo nanoflowers with excellent catalytic efficiency are obtained, where PtCo behaves as oxidase mimic and MnO2 functions as catalase mimic. In this way, the well-defined MnO2@PtCo nanoflowers not only can relieve hypoxic condition but also induce cell apoptosis significantly through ROS-mediated mechanism, thereby resulting in remarkable and specific inhibition of tumor growth.

Selenium-Based Nanozyme as Biomimetic Antioxidant Machinery

A self-assembly nanocomposite was designed to mimic intracellular enzymatic and non-enzymatic antioxidants-constituted antioxidant defense machinery. In this work, selenium nanocomponent served as one model to mimic antioxidant enzyme, whereas polydopamine was able to mimic non-enzymatic antioxidant biomolecule in living systems. With the excellent glutathione peroxidase-mimic capacity of selenium and the reducibility of polydopamine, this Se@pDA nanozyme could achieve synergetic antioxidative efficiency to protect cellular components against oxidative damage. The pneumonia model of mice further proved the potential of our nanocomposites for anti-inflammation therapy.

Polyoxometalate-Coated Magnetic Nanospheres for Highly Selective Isolation of Immunoglobulin G

Polyoxometalate [{a-PW₁₁O₃₉Zr(μ-OH)(H₂O)}₂]^8- (POM1) is first prepared by sandwiching Zr^IV among 2 mono-lacunary α-Keggin polyoxometalates, and then novel magnetic nanoparticles (NPs), Fe₃O₄@polyethyleneimine (PEI)@POM1, are fabricated by coating POM1 onto the surface of magnetic Fe₃O₄@PEI NPs under electrostatic interaction. The obtained Fe₃O₄@PEI@POM1 NPs are characterized by Fourier transform infrared, zeta potential, vibrating sample magnetometer, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. Ascribed to the hydrogen-bonding and electrostatic interactions, the NPs exhibit high adsorption selectivity toward IgG, and the adsorption capacity is high up to 304 mg g^-1 under optimal adsorption conditions. By using 0.01% cetyl trimethylammonium bromide to strip the adsorbed protein species, an elution efficiency of 95% is achieved. The feasibility of Fe₃O₄@PEI@POM1 NPs in real-world sample assay has been demonstrated by the selective isolation of IgG heavy chain and light chain from human serum, as confirmed by the sodium dodecyl sulfate polyacrylamide gel electrophoresis assay.

Integrated nanozymes: facile preparation and biomedical applications

Nanozymes have been viewed as the next generation of artificial enzymes due to their low cost, large specific surface area, and good robustness under extreme conditions. However, the moderate activity and limited selectivity of nanozymes have impeded their usage. To overcome these shortcomings, integrated nanozymes (INAzymes) have been developed by encapsulating two or more different biocatalysts (e.g., natural oxidases and peroxidase mimics) together within confined frameworks. On the one hand, with the assistance of natural enzymes, INAzymes are capable of specifically recognizing targets. On the other hand, nanoscale confinement brought about by integration significantly enhances the cascade reaction efficiency. In this Feature Article, we highlight the newly developed INAzymes, covering from synthetic strategies to versatile applications in biodetection and therapeutics. Moreover, it is predicted that INAzymes with superior activities, specificity, and stability will enrich the research of nanozymes and pave new ways in designing multifunctional nanozymes.

Graphene Oxide Quantum Dots Reduce Oxidative Stress and Inhibit Neurotoxicity In Vitro and In Vivo through Catalase-Like Activity and Metabolic Regulation

Both oxidative stress and neurotoxicity are huge challenges to human health, and effective methods and agents for resisting these adverse effects are limited, especially in vivo. It is shown here that, compared to large graphene oxide (GO) nanosheets, GO quantum dots (GOQDs), as nanozymes, efficiently reduce reactive oxygen species (ROS) and H2O2 in 1-methyl-4-phenyl-pyridinium ion (MPP+)-induced PC12 cells. In addition, GOQDs exert neuroprotective effects in a neuronal cell model by decreasing apoptosis and α-synuclein. GOQDs also efficiently diminish ROS, apoptosis, and mitochondrial damage in zebrafish treated with MPP+. Furthermore, GOQDs-pretreated zebrafish shows increased locomotive activity and Nissl bodies in the brain, confirming that GOQDs ameliorate MPP+-induced neurotoxicity, in contrast to GO nanosheets. GOQDs contribute to neurotoxic amelioration by increasing amino acid metabolism, decreasing tricarboxylic acid cycle activity, and reducing steroid biosynthesis, fatty acid biosynthesis, and galactose metabolic pathway activity, which are related to antioxidation and neurotransmission. Meanwhile, H2O2 decomposition and Fenton reactions suggest the catalase-like activity of GOQDs. GOQDs can translocate into zebrafish brains and exert catalase-mimicking activity to resist oxidation in the intracellular environment. Unlike general nanomaterials, biocompatible GOQDs demonstrate their high potential for human health by reducing oxidative stress and inhibiting neurotoxicity.

A GO-Se nanocomposite as an antioxidant nanozyme for cytoprotection

GO-Se nanocomposites are fabricated with excellent glutathione peroxidase (GPx)-like properties to protect cells against oxidative stress. Compared with SeNPs, the GO-Se nanozymes exhibit higher GPx-mimic catalytic efficiency. Cell experiments further confirm their excellent cytoprotection capacity.

Tau-Targeted Multifunctional Nanocomposite for Combinational Therapy of Alzheimer's Disease

Alzheimer's disease (AD) remains an incurable disease and lacks efficient diagnostic methods. Most AD treatments have focused on amyloid-β (Aβ) targeted therapy; however, it is time to consider the alternative theranostics due to accumulated findings of weak correlation between Aβ deposition and cognition, as well as the failures of Phase III clinical trial on Aβ targeted therapy. Recent studies have shown that the tau pathway is closely associated with clinical development of AD symptoms, which might be a potential therapeutic target. We herein construct a methylene blue (MB, a tau aggregation inhibitor) loaded nanocomposite (CeNC/IONC/MSN-T807), which not only possesses high binding affinity to hyperphosphorylated tau but also inhibits multiple key pathways of tau-associated AD pathogenesis. We demonstrate that these nanocomposites can relieve the AD symptoms by mitigating mitochondrial oxidative stress, suppressing tau hyperphosphorylation, and preventing neuronal death both in vitro and in vivo. The memory deficits of AD rats are significantly rescued upon treatment with MB loaded CeNC/IONC/MSN-T807. Our results indicate that hyperphosphorylated tau-targeted multifunctional nanocomposites could be a promising therapeutic candidate for Alzheimer's disease.

Inhibition of Epithelial-Mesenchymal Transition and Tissue Regeneration by Waterborne Titanium Dioxide Nanoparticles

Titanium dioxide nanoparticles (TiO₂NPs) are among the most widely manufactured nanomaterials with broad applications in food industry, cosmetics, and medicine. Although the toxicity of TiO₂NPs at high doses has been extensively explored, the potential health risks of TiO₂NPs exposure at nontoxic concentrations remain poorly understood. Epithelial-mesenchymal transition (EMT) plays pivotal roles in a diversity of physiological and pathological processes, including tissue regeneration and cancer metastasis. In this study, we find that the cellular uptake of TiO₂NPs inhibits EMT-mediated cell remodeling and cell migration without exhibiting cytotoxicity. Further investigation reveals that TiO₂NPs suppress the process of EMT through the blockade of transforming growth factor-β (TGFβ) signaling. Particularly, TiO₂NPs interact with the TGFβ receptor TβRI/II complex, induce its lysosomal degradation, and thereby downregulate expression of TGFβ target genes. Moreover, we show that waterborne TiO₂NPs do not elicit toxicity in healthy tissues but hamper EMT-mediated wound healing in two animal models. Long-term exposure of TiO₂NPs in environmental water and drinking water impede the regeneration of amputated fin in zebrafish and the recovery of intestinal mucosal damage in colitic mice. Our results reveal the previously unknown effects of TiO₂NPs during tissue remodeling and repair, which have significant implications in their risk assessment and management.

Enzyme-immobilized metal–organic framework nanosheets as tandem catalysts for the generation of nitric oxide

An enzyme-immobilized metal–organic framework nanosystem was developed as a tandem catalyst for in situ generation of nitric oxide in serum samples.

Black Phosphorus Nanosheets as a Neuroprotective Nanomedicine for Neurodegenerative Disorder Therapy

Transition-metal dyshomeostasis is recognized as a critical pathogenic factor at the onset and progression of neurodegenerative disorder (ND). Excess transition-metal ions such as Cu²⁺ can catalyze the generation of cytotoxic reactive oxygen species and thereafter induce neuronal cell apoptosis. Exploring new chelating agents, which are not only capable of capturing excess redox-active metal, but can also cross the blood-brain barrier (BBB), are highly desired for ND therapy. Herein, it is demonstrated that 2D black phosphorus (BP) nanosheets can capture Cu²⁺ efficiently and selectively to protect neuronal cells from Cu²⁺ -induced neurotoxicity. Moreover, both in vitro and in vivo studies show that the BBB permeability of BP nanosheets is significantly improved under near-infrared laser irradiation due to their strong photothermal effect, which overcomes the drawback of conventional chelating agents. Furthermore, the excellent biocompatibility and stability guarantee the biosafety of BP in future clinical applications. Therefore, these features make BP nanosheets have the great potential to work as an efficient neuroprotective nanodrug for ND therapy.

Emerging Biomedical Applications of Enzyme-Like Catalytic Nanomaterials

Nanomaterials have been developed for many biomedical applications, including medical imaging, drug delivery, and antimicrobial coatings. Intriguingly, nanoparticles can display 'enzyme-like' activity and have been explored as alternatives to natural enzymes in several industrial and energy-related applications. Recently, these catalytic nanomaterials with enzyme-mimetic properties have found new biomedical applications, from biofilm disruption to protection against neurodegeneration and tumor prevention. In this review we focus on recent in vivo studies demonstrating potential therapeutic uses of catalytic nanomaterials. We also provide insights about the relationships between catalytic activity, therapeutic efficacy, and biocompatibility that are critical for clinical translatability. Finally, we discuss current challenges and future directions for the use of these nanomaterials as novel platforms for the development of sustainable, affordable, and safe therapeutics.

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.

Quantitatively Intrinsic Biomimetic Catalytic Activity of Nanocerias as Radical Scavengers and Their Ability against H2O2 and Doxorubicin-Induced Oxidative Stress

Artificial enzymes as radical scavengers show great potentials in treatments of various diseases induced by oxidative stress. Herein, the quantitative analysis indicates that the intrinsic activity of nanocerias for the degradation of radicals is determined by the concentration of surface defects as well as their morphological features. The surface Ce³⁺ fraction of the CeO₂ nanozymes with a similar morphology can be used as a descriptor to index their catalytic activity as radical scavengers. Defect-abundant porous nanorods of ceria (PN-CeO₂) with a large surface area (141 m²/g) and high surface Ce³⁺ fraction (32.8%) deliver an excellent catalytic capability for the degradation of radicals, which is 15.5 times higher than that of Trolox. Results indicate that PN-CeO₂ not only provides more surface catalytic centers but also supplies the active site with higher activity. Oxidative stress induced by doxorubicin (Dox), an essential medicine for a wide range of tumors, was used as the model system to evaluate the radical degradation ability of PN-CeO₂. Both in vitro cellar (H9c2 cells) and in vivo animal models revealed that PN-CeO₂ did not affect the cell and rat growth and was able to alleviate the Dox-induced oxidative stress. Results suggest that the artificial PN-CeO₂ nanozymes have potentials to function as an adjuvant medicine during tumor chemotherapy.

Iron oxide nanoparticles may damage to the neural tissue through iron accumulation, oxidative stress, and protein aggregation

BACKGROUND

In the recent decade, iron oxide nanoparticles (IONPs) have been proposed for several applications in the central nervous system (CNS), including targeting amyloid beta (Aβ) in the arteries, inhibiting the microglial cells, delivering drugs, and increasing contrast in magnetic resonance imaging. Conversely, a notable number of studies have reported the role of iron in neurodegenerative diseases. Therefore, this study has reviewed the recent studies to determine whether IONPs iron can threaten the cellular viability same as iron.

RESULTS

Iron contributes in Fenton's reaction and produces reactive oxygen species (ROS). ROS cause to damage the macromolecules and organelles of the cell via oxidative stress. Iron accumulation and oxidative stress are able to aggregate some proteins, including Aβ and α-synuclein, which play a critical role in Alzheimer's and Parkinson's diseases, respectively. Iron accumulation, oxidative stress, and protein aggregation make a positive feedback loop, which can be toxic for the cell. The release of iron ions from IONPs may result in iron accumulation in the targeted tissue, and thus, activate the positive feedback loop. However, the levels of IONPs induced toxicity depend on the size, concentration, surface charge, and the type of coating and functional groups of IONPs.

CONCLUSION

IONPs depending on their properties can lead to iron accumulation, oxidative stress and protein aggregation in the neural cells. Therefore, in order to apply IONPs in the CNS, the consideration of IONPs properties is crucial.

Nanodiamonds Mediate Oral Delivery of Proteins for Stem Cell Activation and Intestinal Remodeling in Drosophila

Introduction of exogenous biomacromolecules into living systems is of great interest in genome editing, cancer immunotherapy, and stem cell reprogramming. Whereas current strategies generally depend on nucleic acids transfection, direct delivery of functional proteins that provides enhanced specificity, increased safety, and fast and temporal regulation is highly desirable. Nevertheless, intracellular delivery of intact and bioactive proteins, especially in vivo, remains poorly explored. In this study, we developed a nanodiamonds (NDs)-based protein delivery system in cultured cells and in Drosophila that showed high adsorption, high efficiency, and effective cytosolic release of fully functional proteins. Through live-cell imaging, we observed a novel phenomenon wherein a substantial amount of internalized NDs-protein complex rejected fusion with the early endosome, thereby evading protein degradation in the lysosome. More significantly, we demonstrated that dietary NDs-RNase induced apoptosis in enterocytes, stimulating regenerative divisions in intestinal stem cells and increasing the number of stem cells and precursor cells in Drosophila intestine. As stem cells are poorly accessible by exogenous agents in vivo, NDs-mediated oral delivery of proteins provides a new approach to modulate the stem cell microenvironment for intestinal remodeling, which has important implications for colorectal cancer therapy and regenerative medicine.

Boosting the Peroxidase-Like Activity of Nanostructured Nickel by Inducing Its 3+ Oxidation State in LaNiO3 Perovskite and Its Application for Biomedical Assays

Catalytic nanomaterials with intrinsic enzyme-like activities, called nanozymes, have recently attracted significant research interest due to their unique advantages relative to natural enzymes and conventional artificial enzymes. Among the nanozymes developed, particular interests have been devoted to nanozymes with peroxidase mimicking activities because of their promising applications in biosensing, bioimaging, biomedicine, etc. Till now, lots of functional nanomaterials have been used to mimic peroxidase. However, few studies have focused on the Ni-based nanomaterials for peroxidase mimics. In this work, we obtained the porous LaNiO₃ nanocubes with high peroxidase-like activity by inducing its 3+ oxidation state in LaNiO₃ perovskite and optimizing the morphology of LaNiO₃ perovskite. The peroxidase mimicking activity of the porous LaNiO₃ nanocubes with Ni³⁺ was about 58~fold and 22~fold higher than that of NiO with Ni²⁺ and Ni nanoparticles with Ni⁰. More, the porous LaNiO₃ nanocubes exhibited about 2-fold higher activity when compared with LaNiO₃ nanoparticles. Based on the superior peroxidase-like activity of porous LaNiO₃ nanocubes, facile colorimetric assays for H₂O₂, glucose, and sarcosine detection were developed. Our present work not only demonstrates a useful strategy for modulating nanozymes' activities but also provides promising bioassays for clinical diagnostics.

Gold nanoparticles enhance the differentiation of embryonic stem cells into dopaminergic neurons via mTOR/p70S6K pathway

AIM

This study aimed to investigate the effect of gold nanoparticles (AuNPs) on differentiation of mouse embryonic stem cells (ESCs) into dopaminergic (DA) neurons and explore the possible underlying molecular mechanisms.

MATERIALS & METHODS

The efficiency of AuNPs on DA neuron differentiation was evaluated by observing fluorescence in TH promoter-engineered GFP-reporter ESCs, western blot and real-time PCR. The possible signal pathway was determined by western blot.

RESULTS

Compared with feeder-free control condition, AuNPs are able to enhance fate specification of ESCs into DA neurons. Moreover, mTOR/p70S6K signaling pathway was found involving in this AuNPs-mediated DA neuron differentiation.

CONCLUSION

Our findings may lead future insight investigation into the underlying mechanisms and potential application of AuNPs in stem cell research.

Graphene Oxide Quantum Dots as Novel Nanozymes for Alcohol Intoxication

Alcohol overconsumption as a worldwide issue results in alcoholic liver disease (ALD), such as steatosis, alcoholic hepatitis, and cirrhosis. The treatment of ALD has been widely investigated but remains challenging. In this work, the protective effects of graphene oxide quantum dots (GOQDs) as novel nanozymes against alcohol overconsumption are discovered, and the specific mechanisms underlying these effects are elucidated via omics analysis. GOQDs dramatically alleviate the reduction of cell viability induced by ethanol and can act as nanozymes to accelerate ethanol metabolism and avoid the accumulation of toxic intermediates in cells. Mitochondrial damage and the excessive generation of free radicals were mitigated by GOQDs. The mechanisms underlying the cellular protective effects were also related to alterations in metabolic and protein signals, especially those involved in lipid metabolism. The moderately increased autophagy induced by GOQDs explained the removal of accumulated lipids and the subsequent elimination of excessive GOQDs. These findings suggest that GOQDs have an antagonistic capacity against the adverse effects caused by ethanol and provide new insights into the direct applications of GOQDs. In addition to traditional antioxidation, this work also establishes metabolomics and proteomics techniques as effective tools to discover the multiple functions of nanozymes.

Advances in DNA Nanostructure-Based Smart Drug Delivery Systems

Highly specific deoxyribonucleic acid (DNA) base-pairing not only carries genetic information, but also provides the basis for self-assembly of novel nanostructures with programmable shapes and sizes. Unlike single-stranded and double-stranded DNA, DNA nanostructures exhibit good cellular permeability. They also have characteristics of uniform size, easy functionalization, precise addressability, excellent water solubility and high biocompatibility. Due to their unique properties, these tailored molecular devices are ideal nanoscale systems for targeting cells and triggering cellular responses. Recent progress in the field of DNA nanotechnology has demonstrated effectiveness and advantages of DNA nanostructures as smart and targeted drug delivery systems or imaging agents within living organisms. In this review, we summarize the recent advances in structure design, cargo loading and cellular delivery of DNA nanocarriers, and discuss their potential in therapeutic applications.

Application of Iron Oxide as a pH-dependent Indicator for Improving the Nutritional Quality

Acid food indicators can be used as pH indicators for evaluating the quality and freshness of fermented products during the full course of distribution. Iron oxide particles are hardly suspended in water, but partially or completely agglomerated. The agglomeration degree of the iron oxide particles depends on the pH. The pH-dependent particle agglomeration or dispersion can be useful for monitoring the acidity of food. The zeta potential of iron oxide showed a decreasing trend as the pH increased from 2 to 8, while the point of zero charge (PZC) was observed around at pH 6.0-7.0. These results suggested that the size of the iron oxide particles was affected by the change in pH levels. As a result, the particle sizes of iron oxide were smaller at lower pH than at neutral pH. In addition, agglomeration of the iron oxide particles increased as the pH increased from 2 to 7. In the time-dependent aggregation test, the average particle size was 730.4 nm and 1,340.3 nm at pH 2 and 7, respectively. These properties of iron oxide particles can be used to develop an ideal acid indicator for food pH and to monitor food quality, besides a colorant or nutrient for nutrition enhancement and sensory promotion in food industry.

Silica Nanoparticles Target a Wnt Signal Transducer for Degradation and Impair Embryonic Development in Zebrafish

Many types of biocompatible nanomaterials have proven of low cytotoxicity and hold great promise for various applications in nanomedicine. Whereas they generally do not cause apparent organ toxicity or tissue damage in adult animals, it is yet to determine their biological consequences in more general contexts. In this study, we investigate how silica nanoparticles (NPs) affect cellular activities and functions under several physiological or pathological conditions. Although silica NPs are generally regarded as "inert" nanocarriers and widely employed in biomedical studies, we find that they actively affect Wnt signaling in various types of cell lines, diminishing its anti-adipogenic effect in preadipocytes and pro-invasive effect in breast cancer cells, and more significantly, impair Wnt-regulated embryonic development in Zebrafish. We further demonstrate that intracellular silica NPs block Wnt signal transduction in a way resembling signaling molecules. Specifically, silica NPs target the Dvl protein, a key component of Wnt signaling cascade, for lysosomal degradation. As Wnt signaling play significant roles in embryonic development and adipogenesis, the observed physiological effects beyond toxicity imply potential risk of obesity, or developmental defects in somitogenesis and osteogenesis upon exposure to silica NPs. In addition, given the clinical implications of Wnt signaling in tumorigenesis and cancer metastasis, our work also establishes for the first time a molecular link between nanomaterials and the Wnt signaling pathway, which opens new door for novel applications of unmodified silica NPs in targeted therapy for cancers and other critical illness.

Iron oxide nanozyme catalyzed synthesis of fluorescent polydopamine for light-up Zn(2+) detection

Fluorescent polydopamine (FPD) is an interesting material with excellent biocompatibility. However, its preparation is currently a lengthy and potentially dangerous process. We herein employ magnetic iron oxide (Fe3O4) nanoparticles as a peroxidase-mimicking nanozyme to produce FPD under mild conditions. Different from previous protocols using multiple steps with up to 6% (∼2 M) H2O2, this preparation takes place in a single step with just 5 mM H2O2 at room temperature. The oxidized product shows excitation-wavelength-dependent emission peaks, similar to previous reports. The reaction kinetics, pH, temperature, and ionic strength are individually optimized. Among a diverse range of other nanomaterials tested, including Fe2O3, CeO2, CoO, Co3O4, NiO, TiO2, gold nanoparticles, and graphene oxide, Fe2O3 and graphene oxide yielded relatively weak emission, while the rest of the materials failed to produce FPD. The Fe3O4 nanoparticles retained ∼90% catalytic activity even after ten cycles of synthesis. Finally, Zn(2+) can enhance the fluorescence of FPD under 360 nm excitation but not under 480 nm excitation, leading to a sensitive light-up sensor with a detection limit of 60 nM Zn(2+). Therefore, this work has demonstrated not only a novel use of nanozymes, but also an interesting application of FPD.