Flexible microneedles incorporating gold nanorods and tacrolimus for effective synergistic photothermal-chemotherapy of rheumatoid arthritis.

Transdermal drug delivery systems for rheumatoid arthritis (RA) have garnered substantial attention due to their great potential to overcome limitations observed in conventional oral or injection strategies, including limited selectivity and adverse effects on extra-articular tissues. Microneedles (MNs) appear to be highly desirable carriers for transdermal drug delivery of RA. However, microneedles typically are unable to keep up with the flexibility of joints, which decreases the effectiveness of administration. In this study, we developed a flexible microneedles (FMNs) delivery system. And gelatin was employed for the fabrication of flexible backings for microneedles owing to its excellent ductility and biocompatibility. We achieved synergisticphotothermal-chemotherapy of RA by incorporating the chemical drug Tacrolimus (TAC) and the photothermal agent gold nanorods (AuNRs) into dissolving microneedles. Results showed a high mechanical strength of the proposed FMNs. In the animal model of adjuvant-induced arthritis (AA), it is indicated that the prepared FMNs inhibited the expression of related inflammatory cytokines such as IL-1ß and TNF-α while enhancing bone repair and other related factors. Thus, the combination therapy of FMNs-mediated hyperthermia and chemotherapy can serve as a novel and synergistic treatment option for RA.

Fabrication of controlled porous and ultrafast dissolution porous microneedles by organic-solvent-free ice templating method.

Porous Microneedles (PMNs) have been widely used in drug delivery and medical diagnosis owing to their abundant interconnected pores. However, the mechanical strength, the use of organic solvent, and drug loading capacity have long been challenging. Herein, a novel strategy of PMNs fabrication based on the Ice Templating Method is proposed that is suitable for insoluble, soluble, and nanosystem drug loading. The preparation process simplifies the traditional microneedle preparation process with a shorter preparation time. It endows the highly tunable porous morphology, enhanced mechanical strength, and rapid dissolution performance. Micro-CT three-dimensional reconstruction was used to better quantify the internal structures of PMNs, and we further established the equivalent pore network model to statistically analyze the internal pore structure parameters of PMNs. In particular, the mechanical strength is mainly negatively correlated with the surface porosity, while the dissolution velocity is mainly positively correlated with the permeability coefficient by the correlation heatmap. The poorly water-soluble Asiatic acid was encapsulated in PMNs in nanostructured lipid carriers, showing prominent hypertrophic scar healing trends. This work offers a quick and easy way of preparation that may be used to expand PMNs function and be introduced in industrial manufacturing development.

MgO@polydopamine Nanoparticle-Loaded Photothermal Microneedle Patches Combined with Chitosan Gel Dressings for the Treatment of Infectious Wounds.

As for wound drug delivery, microneedles (MNs) have attracted wide attention. However, while effective at increasing the depth of drug delivery, traditional MNs often have limited drug loads and have difficulty penetrating scabs on wounds. Herein, we develop a drug delivery system combining MgO@polydopamine (MgO@PDA) nanoparticle-loaded photothermal MN patches and chitosan (CS) gel to inhibit the formation of scabs and deliver sufficient drugs into deep tissue. When inserted into the wound, the MN system can keep the wound bed moist and weakly acidic to inhibit the formation of scabs and accelerate wound closure. The released MgO@PDA nanoparticles from both the tips and the backing layer, which immensely increase the drug load, continuously release Mg2+ in the moist, weakly acidic wound bed, promoting tissue migration and the formation of microvessels. MgO@PDA nanoparticles show excellent antibacterial activity under near-infrared irradiation synergized with the CS gel, and the PDA coating can also overcome the adverse effects of oxidative stress. Through in vitro and in vivo experiments, the MN system showed remarkable antibacterial, antioxidant, anti-inflammatory, and pro-angiogenic effects, indicating its potential in the treatment of infectious wounds.

Enhanced Production of Sisomicin in Micromonospora inyoensis by Protoplast Mutagenesis and Fermentation Optimization.

Sisomicin is a broad-spectrum aminoglycoside antibiotic and is the precursor of netilmicin and plazomicin. However, the fermentation level of sisomicin is still low compared with other antibiotics, which restricts the application of sisomicin and its derivatives. In this study, to improve sisomicin production, breeding of high-yielding sisomicin strains was conducted with chemical mutagenesis using Micromonospora inyoensis OG-1 (titer, 1042 U·mL-1) as the starting strain. Protoplast preparation was conducted under optimal conditions, and protoplast mutagenesis was performed with a suitable concentration of diethyl sulfate. Subsequently, a high-yielding and genetically stable strain (H6-32) was obtained by screening, with a sisomicin titer of 1486 U·mL-1 (an increase of 42.6%). Finally, carbon and nitrogen sources were optimized to further improve sisomicin production, and a sisomicin titer of 1780 U·mL-1 was ultimately obtained by controlling the dissolved oxygen level at 30% in a 5-L fermenter, which to the best of our knowledge is the highest reported titer ever achieved by fermentation. Comparative genome analysis showed that a total of 13 genes in the genome of the mutant strain H6-32 were mutated compared to the original strain. This study not only provides a reference for further breeding of high-yielding strains and fermentation optimization, but also enhances our understanding of sisomicin production.

Methotrexate-loaded hyaluronan-modified liposomes integrated into dissolving microneedles for the treatment of psoriasis.

Methotrexate (MTX) is a first-line drug in treating psoriasis because of its strong anti-proliferation and anti-inflammatory effects. However, systemic administration of MTX will lead to many side effects, such as gastrointestinal irritation, liver and kidney toxicity, etc. Herein, we developed liposome-loaded microneedles (MNs) system to improve transdermal efficiency, which was used to overcome the problems of low transdermal efficiency and poor therapeutic effect of traditional transdermal drug delivery methods. Hyaluronic acid (HA) was modified on the surface of MTX-loaded liposomes. The interaction of HA and CD44 could increase the adhesion of HA-MTX-Lipo to HaCaT cells, thereby promoting the apoptosis or death of HaCaT cells. Results indicated HA-MTX-Lipo MNs could inhibit the development of psoriasis and reduce the degree of skin erythema, scaling, and thickening. The mRNA levels of proinflammatory cytokines such as IL-17A, IL-23, and TNF-α were decreased. The epidermal thickness and proliferative cell-associated antigen Ki67 expression were also reduced. Specifically, the expression of mRNA levels of proinflammatory cytokines was down-regulated. The MNs transdermal delivery of HA-modified-MTX liposomes provided a promising method for treating psoriasis.

Identification of the High-Affinity Potassium Transporter Gene Family (HKT) in Brassica U-Triangle Species and Its Potential Roles in Abiotic Stress in Brassica napus L.

Members of the high-affinity potassium transporter (HKT) protein family regulate the uptake and homeostasis of sodium and potassium ions, but little research describes their roles in response to abiotic stresses in rapeseed (Brassica napus L.). In this study, we identified and characterized a total of 36 HKT genes from the species comprising the triangle of U model (U-triangle species): B. rapa, B. nigra, B. oleracea, B. juncea, B. napus, and B. carinata. We analyzed the phylogenetic relationships, gene structures, motif compositions, and chromosomal distributions of the HKT family members of rapeseed. Based on their phylogenetic relationships and assemblage of functional domains, we classified the HKT members into four subgroups, HKT1;1 to HKT1;4. Analysis of the nonsynonymous substitutions (Ka), synonymous substitutions (Ks), and the Ka/Ks ratios of HKT gene pairs suggested that these genes have experienced strong purifying selective pressure after duplication, with their evolutionary relationships supporting the U-triangle theory. Furthermore, the expression profiles of BnaHKT genes varies among potassium, phytohormone and heavy-metal treatment. Their repression provides resistance to heavy-metal stress, possibly by limiting uptake. Our results systematically reveal the characteristics of HKT family proteins and their encoding genes in six Brassica species and lay a foundation for further exploration of the role of HKT family genes in heavy-metal tolerance.

Four New Species of Small-Spored Alternaria Isolated from Solanum tuberosum and S. lycopersicum in China.

Small-spored Alternaria species have been frequently isolated from diseased leaves of Solanum plants. To clarify the diversity of small-spored Alternaria species, a total of 118 strains were obtained from leaf samples of S. tuberosum and S. lycopersicum in six provinces of China during 2022-2023. Based on morphological characterization and multi-locus phylogenetic analysis of the internal transcribed spacer of the rDNA region (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1 alpha (TEF1), RNA polymerase second largest subunit (RPB2), Alternaria major allergen gene (Alt a 1), endopolygalacturonase gene (EndoPG) and an anonymous gene region (OPA10-2), seven species were determined, including four novel species and three known species (A. alternata, A. gossypina and A. arborescens). The novel species were described and illustrated as A. longxiensis sp. nov., A. lijiangensis sp. nov., A. lycopersici sp. nov. and A. solanicola sp. nov.. In addition, the pathogenicity of the seven species was evaluated on potato leaves. The species exhibited various aggressiveness, which could help in disease management.

Comparative genomic analyses reveal the genetic basis of the yellow-seed trait in Brassica napus.

Yellow-seed trait is a desirable breeding characteristic of rapeseed (Brassica napus) that could greatly improve seed oil yield and quality. However, the underlying mechanisms controlling this phenotype in B. napus plants are difficult to discern because of their complexity. Here, we assemble high-quality genomes of yellow-seeded (GH06) and black-seeded (ZY821). Combining in-depth fine mapping of a quantitative trait locus (QTL) for seed color with other omics data reveal BnA09MYB47a, encoding an R2R3-MYB-type transcription factor, as the causal gene of a major QTL controlling the yellow-seed trait. Functional studies show that sequence variation of BnA09MYB47a underlies the functional divergence between the yellow- and black-seeded B. napus. The black-seed allele BnA09MYB47aZY821, but not the yellow-seed allele BnA09MYB47aGH06, promotes flavonoid biosynthesis by directly activating the expression of BnTT18. Our discovery suggests a possible approach to breeding B. napus for improved commercial value and facilitates flavonoid biosynthesis studies in Brassica crops.

Genome-Wide Association Study of Glucosinolate Metabolites (mGWAS) in Brassica napus L.

Glucosinolates (GSLs) are secondary plant metabolites that are enriched in rapeseed and related Brassica species, and they play important roles in defense due to their anti-nutritive and toxic properties. Here, we conducted a genome-wide association study of six glucosinolate metabolites (mGWAS) in rapeseed, including three aliphatic glucosinolates (m145 gluconapin, m150 glucobrassicanapin and m151 progoitrin), one aromatic glucosinolate (m157 gluconasturtiin) and two indole glucosinolates (m165 indolylmethyl glucosinolate and m172 4-hydroxyglucobrassicin), respectively. We identified 113 candidate intervals significantly associated with these six glucosinolate metabolites. In the genomic regions linked to the mGWAS peaks, 187 candidate genes involved in glucosinolate biosynthesis (e.g., BnaMAM1, BnaGGP1, BnaSUR1 and BnaMYB51) and novel genes (e.g., BnaMYB44, BnaERF025, BnaE2FC, BnaNAC102 and BnaDREB1D) were predicted based on the mGWAS, combined with analysis of differentially expressed genes. Our results provide insight into the genetic basis of glucosinolate biosynthesis in rapeseed and should facilitate marker-based breeding for improved seed quality in Brassica species.

High-Speed railways and the spread of Covid-19.

High-speed railways (HSRs) greatly decrease transportation costs and facilitate the movement of goods, services, and passengers across cities. In the context of the Covid-19 pandemic, however, HSRs may contribute to the cross-regional spread of the new coronavirus. This paper evaluates the role of HSRs in spreading Covid-19 from Wuhan to other Chinese cities. We use train frequencies in 1971 and 1990 as instrumental variables. Empirical results from gravity models demonstrate that one more HSR train originating from Wuhan each day before the Wuhan lockdown increases the cumulative number of Covid-19 cases in a city by about 10 percent. The empirical analysis suggests that other transportation modes, including normal-speed trains and airline flights, also contribute to the spread of Covid-19, but their effects are smaller than the effect of HSRs. This paper's findings indicate that transportation infrastructures, especially HSR trains originating from a city where a pandemic broke out, can be important factors promoting the spread of an infectious disease.

The Finite Element Analysis Research on Microneedle Design Strategy and Transdermal Drug Delivery System.

Microneedles (MNs) as a novel transdermal drug delivery system have shown great potential for therapeutic and disease diagnosis applications by continually providing minimally invasive, portable, cost-effective, high bioavailability, and easy-to-use tools compared to traditional parenteral administrations. However, microneedle transdermal drug delivery is still in its infancy. Many research studies need further in-depth exploration, such as safety, structural characteristics, and drug loading performance evaluation. Finite element analysis (FEA) uses mathematical approximations to simulate real physical systems (geometry and load conditions). It can simplify complex engineering problems to guide the precise preparation and potential industrialization of microneedles, which has attracted extensive attention. This article introduces FEA research for microneedle transdermal drug delivery systems, focusing on microneedle design strategy, skin mechanics models, skin permeability, and the FEA research on drug delivery by MNs.

Multi-omics analysis reveals the mechanism of seed coat color formation in Brassica rapa L.

KEYMESSAGE: Multi-omics analysis of the transcriptome, metabolome and genome identified major and minor loci and candidate genes for seed coat color and explored the mechanism of flavonoid metabolites biosynthesis in Brassica rapa. Yellow seed trait is considered an agronomically desirable trait with great potential for improving seed quality of Brassica crops. Mechanisms of the yellow seed trait are complex and not well understood. In this study, we performed an integrated metabolome, transcriptome and genome-wide association study (GWAS) on different B. rapa varieties to explore the mechanisms underlying the seed coat color formation. A total of 2,499 differentially expressed genes and 116 differential metabolites between yellow and black seeds with strong association with the flavonoid biosynthesis pathway was identified. In addition, 330 hub genes involved in the seed coat color formation, and the most significantly differential flavonoids biosynthesis were detected based on weighted gene co-expression network analysis. Metabolite GWAS analysis using the contents of 42 flavonoids in developing seeds of 159 B. rapa lines resulted in the identification of 1,626 quantitative trait nucleotides (QTNs) and 37 chromosomal intervals, including one major locus on chromosome A09. A combination of QTNs detection, transcriptome and functional analyses led to the identification of 241 candidate genes that were associated with different flavonoid metabolites. The flavonoid biosynthesis pathway in B. rapa was assembled based on the identified flavonoid metabolites and candidate genes. Furthermore, BrMYB111 members (BraA09g004490.3C and BraA06g034790.3C) involved in the biosynthesis of taxifolin were functionally analyzed in vitro. Our findings lay a foundation and provide a reference for systematically investigating the mechanism of seed coat color in B. rapa and in the other plants.

Genome-Wide Identification of the TIFY Gene Family in Brassiceae and Its Potential Association with Heavy Metal Stress in Rapeseed.

The TIFY gene family plays important roles in various plant biological processes and responses to stress and hormones. The chromosome-level genome of the Brassiceae species has been released, but knowledge concerning the TIFY family is lacking in the Brassiceae species. The current study performed a bioinformatics analysis on the TIFY family comparing three diploid (B. rapa, B. nigra, and B. oleracea) and two derived allotetraploid species (B. juncea, and B. napus). A total of 237 putative TIFY proteins were identified from five Brassiceae species, and classified into ten subfamilies (six JAZ types, one PPD type, two TIFY types, and one ZML type) based on their phylogenetic relationships with TIFY proteins in A. thaliana and Brassiceae species. Duplication and synteny analysis revealed that segmental and tandem duplications led to the expansion of the TIFY family genes during the process of polyploidization, and most of these TIFY family genes (TIFYs) were subjected to purifying selection after duplication based on Ka/Ks values. The spatial and temporal expression patterns indicated that different groups of BnaTIFYs have distinct spatiotemporal expression patterns under normal conditions and heavy metal stresses. Most of the JAZIII subfamily members were highest in all tissues, but JAZ subfamily members were strongly induced by heavy metal stresses. BnaTIFY34, BnaTIFY59, BnaTIFY21 and BnaTIFY68 were significantly upregulated mostly under As3+ and Cd2+ treatment, indicating that they could be actively induced by heavy metal stress. Our results may contribute to further exploration of TIFYs, and provided valuable information for further studies of TIFYs in plant tolerance to heavy metal stress.

Metabolite Characteristics Analysis of Siliques and Effects of Lights on the Accumulation of Glucosinolates in Siliques of Rapeseed.

Glucosinolates (GSLs) are naturally occurring secondary metabolites found in the Brassicaceae family, which mainly synthesize in the siliques with a wide range of functions. In this study, we investigated the effects of lights on metabolites in siliques of rapeseed through ultra high-performance liquid chromatography (UPLC)-heated electrospray ionization (HESI)-tandem mass spectrometry (MS/MS). A total of 249 metabolites, including 29 phenolic acids, 38 flavonoids, 22 GSLs, 93 uncalculated and 67 unknown compounds, were identified in siliques of rapeseed. Meanwhile, 62 metabolites showed significant differences after shading treatment, which were mainly GSLs and unknown compounds. Interestingly, the amounts of 10 GSLs had high accumulation levels in siliques, while the expression levels of their corresponding biosynthetic genes (AOP, GSL-OH, IGMT, and ST5a) were obviously reduced after shading treatment. Further evidence showed that the amounts of GSLs were significantly reduced in seeds, in accordance with the expression profiles of transporter genes (BnaGTRs). Our findings indicated that lights could affect the accumulation and transportation of GSLs from siliques to seeds in rapeseed. Therefore, this study facilitates a better understanding of metabolic characteristics of siliques and provides insight into the importance of light for GSLs accumulation and transportation in siliques and seeds of rapeseed.

Local Housing Market Sentiments and Returns: Evidence from China.

This paper examines the impacts of local housing sentiments on the housing price dynamics of China. With a massive second-hand transaction dataset, we construct monthly local housing sentiment indices for 18 major cities in China from January 2016 to October 2020. We create three sentiment proxies representing the local housing market liquidity and speculative behaviors from the transaction dataset and then use partial least squares (PLS) to extract a recursive look-ahead-bias-free local housing sentiment index for each city considered. The local housing sentiments are shown to have robust predictive powers for future housing returns with a salient short-run underreaction and long-run overreaction pattern. Further analysis shows that local housing sentiment impacts are asymmetric, and housing returns in cities with relatively inelastic housing supply are more sensitive to local housing sentiments. We also document a significant feedback effect between housing returns and market sentiments, indicating the existence of a pricing-sentiment spiral which could potentially enhance the ongoing market fever of Chinese housing markets. The main estimation results are robust to alternative sentiment extraction methods and alternative sentiment proxies, and consistent for the sample period before COVID-19.

Finite Element Analysis for Biodegradable Dissolving Microneedle Materials on Skin Puncture and Mechanical Performance Evaluation.

In this study, a micro-molding technology was used to prepare the microneedles (MNs), while a texture analyzer was used to measure its Young's modulus, Poisson's ratio and compression breaking force, to evaluate whether the MNs can penetrate the skin. The effects of different materials were characterized by their ability to withstand stresses using the Structural Mechanics Module of COMSOL Multiphysics. Carboxymethylcellulose (CMC) was chosen as the needle formulation material with varying quantities of polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA) and hyaluronic acid (HA) to adjust the viscosity, brittleness, hardness and solubility of the material. The results of both the experimental tests and the predictions indicated that the hardest tip material had a solids content of 15% (w/w ) with a 1:2 (w/w) CMC: HA ratio. Furthermore, it was shown that a solid content of 10% (w/w) with a 1:5 (w/w) CMC: PVA ratio is suitable for making patches. The correlation between the mechanical properties and the different materials was found using the simulation analysis as well as the force required for different dissolving microneedles (DMNs) to penetrate the skin, which significantly promoted the research progress of microneedle transdermal drug delivery.

Metabolite Profiling and Transcriptome Analysis Provide Insight into Seed Coat Color in Brassica juncea.

The allotetraploid species Brassica juncea (mustard) is grown worldwide as oilseed and vegetable crops; the yellow seed-color trait is particularly important for oilseed crops. Here, to examine the factors affecting seed coat color, we performed a metabolic and transcriptomic analysis of yellow- and dark-seeded B. juncea seeds. In this study, we identified 236 compounds, including 31 phenolic acids, 47 flavonoids, 17 glucosinolates, 38 lipids, 69 other hydroxycinnamic acid compounds, and 34 novel unknown compounds. Of these, 36 compounds (especially epicatechin and its derivatives) accumulated significantly different levels during the development of yellow- and dark-seeded B. juncea. In addition, the transcript levels of BjuDFR, BjuANS,BjuBAN, BjuTT8, and BjuTT19 were closely associated with changes to epicatechin and its derivatives during seed development, implicating this pathway in the seed coat color determinant in B. juncea. Furthermore, we found numerous variations of sequences in the TT8A genes that may be associated with the stability of seed coat color in B. rapa, B. napus, and B. juncea, which might have undergone functional differentiation during polyploidization in the Brassica species. The results provide valuable information for understanding the accumulation of metabolites in the seed coat color of B. juncea and lay a foundation for exploring the underlying mechanism.

Genome-wide identification and comparative analysis of diacylglycerol kinase (DGK) gene family and their expression profiling in Brassica napus under abiotic stress.

BACKGROUND: Diacylglycerol kinases (DGKs) are signaling enzymes that play pivotal roles in response to abiotic and biotic stresses by phosphorylating diacylglycerol (DAG) to form phosphatidic acid (PA). However, no comprehensive analysis of the DGK gene family had previously been reported in B. napus and its diploid progenitors (B. rapa and B. oleracea). RESULTS: In present study, we identified 21, 10, and 11 DGK genes from B. napus, B. rapa, and B. oleracea, respectively, which all contained conserved catalytic domain and were further divided into three clusters. Molecular evolutionary analysis showed that speciation and whole-genome triplication (WGT) was critical for the divergence of duplicated DGK genes. RNA-seq transcriptome data revealed that, with the exception of BnaDGK4 and BnaDGK6, BnaDGK genes have divergent expression patterns in most tissues. Furthermore, some DGK genes were upregulated or downregulated in response to hormone treatment and metal ion (arsenic and cadmium) stress. Quantitative real-time PCR analysis revealed that different BnaDGK genes contribute to seed oil content. CONCLUSIONS: Together, our results indicate that DGK genes have diverse roles in plant growth and development, hormone response, and metal ion stress, and in determining seed oil content, and lay a foundation for further elucidating the roles of DGKs in Brassica species.

Genome-wide identification AINTEGUMENTA-like (AIL) genes in Brassica species and expression patterns during reproductive development in Brassica napus L.

The AINTEGUMENTA-like (AIL) proteins, which belong to the AP2 family, play important roles in regulating the growth and development of plant organs. The AIL family has not yet been comprehensively studied in rapeseed (Brassica napus), an allotetraploid and model organism for the study of polyploid evolution. In the present study, 99 AIL family genes were identified and characterized from B. rapa, B. oleracea, B. napus, B. juncea, and B. nigra using a comprehensive genome-wide study, including analyses of phylogeny, gene structure, chromosomal localization, and expression pattern. Using a phylogenetic analysis, the AIL genes were divided into eight groups, which were closely related to the eight AtAIL genes, and which shared highly conserved structural features within the same subfamily. The non-synonymous/synonymous substitution ratios of the paralogs and orthologs were less than 1, suggesting that the AIL genes mainly experienced purifying selection during evolution. In addition, the RNA sequencing data and qRT-PCR analysis revealed that the B. napus AIL genes exhibited organ- and developmental stage-specific expression patterns. Certain genes were highly expressed in the developing seeds (BnaAIL1, BnaAIL2, BnaAIL5, and BnaAIL6), the roots (BnaANT, BnaAIL5, and BnaAIL6), and the stem (BnaAIL7B). Our results provide valuable information for further functional analysis of the AIL family in B. napus and related Brassica species.

Graphene oxide induced assembly and crumpling of Co3O4 nanoplates.

Cobalt (II, III) oxide (Co3O4) has been widely studied and applied in various fields, however, it suffers from slow mass and electron transfer during applications. Herein, crumpled Co3O4 and Co3O4/reduced graphene oxide (rGO) with tunable 2D-in-3D structures were prepared by combining spray pyrolysis with a graphene oxide (GO) template. The 2D Co3O4 nanoplates were interconnected with each other to form a 3D ball with many wrinkles, resulting in defect enrichment on the abundant boundaries of the nanosheets, which provided more active sites for catalytic reactions. In addition, the unique 2D-in-3D structure allowed fast mass transfer and structural stability. Furthermore, the assembled structure could be understood as being composed of uniformly distributed oxygen-containing functional groups pinning metal cations on the GO surface through electrostatic interaction, and the 2D structure of the GO enabled the in situ converted Co3O4 to grow along the GO surface with excellent dispersion. Taking advantage of the above, the Co3O4/rGO balls demonstrated an excellent oxygen evolution reaction performance, an overpotential of 298 mV at a current density of 10.0 mA cm-2 and a current density of 115.9 mA cm-2 at the overpotential of η = 500 mV.