Antibiotic Resistance Characterization and Molecular Characteristics of Enterococcus Species Isolated from Combination Probiotic Preparations in China.

Enterococci can act as reservoirs for antibiotic-resistant genes that are potentially at risk of being transferred to other bacteria that inhabit in the gastrointestinal tract. The aim of this study was to determine the phenotypic and molecular characteristics of antibiotic-resistant enterococci isolated from probiotic preparations. In total, we isolated 15 suspected Enterococcus species from 5 compound probiotics, which were identified by 16S rDNA as 12 Enterococcus faecium and 3 Enterococcus faecalis. Determination of antimicrobial susceptibility by the microdilution broth method showed widespread resistance to sulfamethoxazole (100%), norfloxacin (99.3%), azithromycin (99.3%), gentamicin (86.7%), and chloramphenicol (20%). Whole genome sequencing of five resistant strains revealed that all had circular DNA chromosomes and that E. faecium J-1-A to J-4-A contained a plasmid, while E. faecalis J-5-A did not. The results of the resistance gene analysis revealed that each strain contained approximately 30 resistance genes, with the antibiotic resistance genes and the multidrug resistance efflux pump genes mdtG, lmrC, and lmrD detected in all strains. The chloramphenicol resistance genes ykkC and ykkD were first identified in E. faecalis. And there were 21, 19, 21, 21, and 29 virulence factors involved in strains, respectively. Further analysis of the gene islands (GIs) revealed that each strain contained more than 10 GIs. The above results confirm the existence of hidden dangers in the safety of probiotics and remind us to carefully select probiotic preparations containing enterococcal strains to avoid the potential spread of resistance and pathogenicity.

Matrine Protects Endothelial Progenitor Cells against Apoptosis and Promotes Their Migration, Invasion, and Tube Formation Abilities via Modulating miR-126b/FOXO4 Axis.

INTRODUCTION AND OBJECTIVE: Endothelial progenitor cells (EPCs) have been proven to exhibit a therapeutic effect in deep vein thrombosis, but are susceptible to microenvironment. Besides, Matrine has promotive effects on EPCs, but its effects on microRNA (miR)-126 remain obscure, which are therefore discussed in the study. METHODS: The cultured EPCs were extracted from Sprague-Dawley rats and identified by immunofluorescence assay. After being treated with Matrine or transfected with miR-126b inhibitor and small interfering RNA targeting forkhead box (FOXO) 4, the viability and apoptosis of EPCs were determined by cell counting kit-8 assay and flow cytometry. The migration, invasion, and tube formation abilities were detected by scratch, Transwell, and tube formation assays. The target genes of miR-126b were predicted by TargetScan, and verified by dual-luciferase reporter assay. The expressions of miR-126b, FOXO4, matrix metalloproteinase (MMP) 2, MMP9, and vascular endothelial growth factor (VEGF) A were determined by quantitative real-time polymerase chain reaction and Western blot. RESULTS: The EPCs were successfully extracted and cultured, as evidenced by positive reaction cluster of differentiation (CD) 34 and CD133. Matrine promoted the viability, migration, invasion, and tube formation while inhibiting the apoptosis of EPCs, and upregulated the expression of miR-126b. Besides, miR-126b inhibitor reversed the effects of Matrine on EPCs and downregulated the expression levels of MMP2, MMP9, and VEGFA. MiR-126b targeted the FOXO4, and siFOXO4 reversed the abovementioned effects of miR-126b inhibitor on EPCs. CONCLUSION: Matrine protects EPCs from apoptosis and promotes their migration, invasion, and tube formation abilities via regulating miR-126b/FOXO4 axis.

Circ_LAS1L regulates cardiac fibroblast activation, growth, and migration through miR-125b/SFRP5 pathway.

Current studies have shown that circular RNAs (circRNAs) and microRNAs (miRNAs) are closely related in acute myocardial infarction (AMI). Previous studies have shown that miR-125b promotes fibrosis and up-regulates in cardiac fibroblasts (CFs), and further experiments showed that circ_LAS1L had multiple binding sites of miR-125b, and their expression was inversely related in AMI patients and CFs. RNA immunoprecipitation (RIP), pull down, and dual luciferase reporter gene assay all confirmed that miR-125b directly bound to circ_LAS1L. Circ_LAS1L overexpression promoted the expression of downstream target gene secreted frizzled-related protein 5 (SFRP5), inhibited the expression of alpha-SMA, collagen I, and collagen III, inhibited CF proliferation and migration, and promoted apoptosis. When cotransfected with circ_LAS1L overexpression vector and miR-125b mimics, the above gene expression and CF biological behaviours did not change significantly. But when cotransfected with circ_LAS1L overexpression vector and SFRP5 siRNA, SFRP5 expression was still down-regulated, the expression of alpha-SMA, collagen I, and collagen III was up-regulated, and the proliferation and migration of CFs were increased. Therefore, circ_LAS1L inhibits the activity of miR-125b by adsorbing it, thus promoting the expression of SFRP5 and then regulating the biological characteristics of CFs. These findings may provide an important experimental basis for the regulation of myocardial fibrosis after myocardial infarction. SIGNIFICANCE OF THE STUDY: Studies have shown that circular RNAs (circRNAs) play important roles in cardiovascular diseases, but there are few studies on their roles in the process of myocardial fibrosis. In this study, we found that circ_LAS1L was down-regulated in acute myocardial infarction (AMI) patients and cardiac fibroblasts (CFs), and could bind directly to miR-125b, thereby promoting the expression of downstream target gene secreted frizzled-related protein 5 (SFRP5), ultimately inhibiting the activation, proliferation and migration of CF, and promoting apoptosis. This suggests that circ_LAS1L/miR-125b/SFRP5 pathway can regulate the biological function of CF and may play an important role in the process of myocardial fibrosis, thus providing an important theoretical basis for the regulation of myocardial fibrosis after myocardial infarction.

Effects of carbon-based impurities on graphene growth.

In this paper, we studied the growth of graphene on an untreated Cu substrate and further studied the effect of carbon-based impurities on the nucleation of graphene in different growth environments. It is found that the impurities on the surface of the Cu substrate easily lead to damage of the graphene, and the impurities do not always promote nucleation as previously reported, but inhibit nucleation in a high etching environment. Finally, based on experimental results, a model of nucleation and growth of graphene around impurities is presented.

A Robust Hybrid Zn-Battery with Ultralong Cycle Life.

Advanced batteries with long cycle life and capable of harnessing more energies from multiple electrochemical reactions are both fundamentally interesting and practically attractive. Herein, we report a robust hybrid zinc-battery that makes use of transition-metal-based redox reaction (M-O-OH → M-O, M = Ni and Co) and oxygen reduction reaction (ORR) to deliver more electrochemical energies of comparably higher voltage with much longer cycle life. The hybrid battery was constructed using an integrated electrode of NiCo2O4 nanowire arrays grown on carbon-coated nickel foam, coupled with a zinc plate anode in alkaline electrolyte. Benefitted from the M-O/M-O-OH redox reactions and rich ORR active sites in NiCo2O4, the battery has concurrently exhibited high working voltage (by M-O-OH → M-O) and high energy density (by ORR). The good oxygen evolution reaction (OER) activity of the electrode and the reversible M-O ↔ M-O-OH reactions also enabled smooth recharging of the batteries, leading to excellent cycling stabilities. Impressively, the hybrid batteries maintained highly stable charge-discharge voltage profile under various testing conditions, for example, almost no change was observed over 5000 cycles at a current density of 5 mA cm-2 after some initial stabilization. With merits of higher working voltage, high energy density, and ultralong cycle life, such hybrid batteries promise high potential for practical applications.

Heterogeneous Electrocatalyst with Molecular Cobalt Ions Serving as the Center of Active Sites.

Molecular Co2+ ions were grafted onto doped graphene in a coordination environment, resulting in the formation of molecularly well-defined, highly active electrocatalytic sites at a heterogeneous interface for the oxygen evolution reaction (OER). The S dopants of graphene are suggested to be one of the binding sites and to be responsible for improving the intrinsic activity of the Co sites. The turnover frequency of such Co sites is greater than that of many Co-based nanostructures and IrO2 catalysts. Through a series of carefully designed experiments, the pathway for the evolution of the Co cation-based molecular catalyst for the OER was further demonstrated on such a single Co-ion site for the first time. The Co2+ ions were successively oxidized to Co3+ and Co4+ states prior to the OER. The sequential oxidation was coupled with the transfer of different numbers of protons/hydroxides and generated an active Co4+═O fragment. A side-on hydroperoxo ligand of the Co4+ site is proposed as a key intermediate for the formation of dioxygen.

Co@Co3 O4 @PPD Core@bishell Nanoparticle-Based Composite as an Efficient Electrocatalyst for Oxygen Reduction Reaction.

Durable electrocatalysts with high catalytic activity toward oxygen reduction reaction (ORR) are crucial to high-performance primary zinc-air batteries (ZnABs) and direct methanol fuel cells (DMFCs). An efficient composite electrocatalyst, Co@Co3 O4 core@shell nanoparticles (NPs) embedded in pyrolyzed polydopamine (PPD) is reported, i.e., in Co@Co3 O4 @PPD core@bishell structure, obtained via a three-step sequential process involving hydrothermal synthesis, high temperature calcination under nitrogen atmosphere, and gentle heating in air. With Co@Co3 O4 NPs encapsulated by ultrathin highly graphitized N-doped carbon, the catalyst exhibits excellent stability in aqueous alkaline solution over extended period and good tolerance to methanol crossover effect. The integration of N-doped graphitic carbon outer shell and ultrathin nanocrystalline Co3 O4 inner shell enable high ORR activity of the core@bishell NPs, as evidenced by ZnABs using catalyst of Co@Co3 O4 @PPD in air-cathode which delivers a stable voltage profile over 40 h at a discharge current density of as high as 20 mA cm(-2) .

Realizing controllable graphene nucleation by regulating the competition of hydrogen and oxygen during chemical vapor deposition heating.

Oxygen can passivate Cu surface active sites when graphene nucleates. Thus, the nucleation density is decreased. The CuO/Cu substrate was chosen for graphene domain synthesis in our study. The results indicate that the CuO/Cu substrate is beneficial for large-scale, single-crystal graphene domain synthesis. Graphene grown on the CuO/Cu substrate exhibits fewer nucleation sites than on Cu foils, suggesting that graphene follows an oxygen-dominating growth. Hydrogen treatment via a heating process could weaken the surface oxygen's role in limiting graphene nucleation under the competition of hydrogen and oxygen and could transfer the synthesis of graphene into a hydrogen-dominating growth. However, the competition only exists during the chemical vapor deposition heating process. For non-hydrogen heated samples, oxygen-dominating growth is experienced even though the samples are annealed in hydrogen for a long time after the heating process. With the temperature increases, the role of hydrogen gradually decreases. The balance of hydrogen and oxygen is adjusted by introducing hydrogen gas at a different heating temperatures. The oxygen concentration on the substrate surface is believed to determine the reactions mechanisms based on the secondary ion mass spectrometry test results. This study provides a new method for the controllable synthesis of graphene nucleation during a heating process.

A Flexible Electrode Based on Iron Phosphide Nanotubes for Overall Water Splitting.

The design of cheap and efficient water splitting systems for sustainable hydrogen production has attracted increasing attention. A flexible electrode, based on carbon cloth substrate and iron phosphide nanotubes coated with an iron oxide/phosphate layer, is shown to catalyze overall water splitting. The as-prepared flexible electrode demonstrates remarkable electrocatalytic activity for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) at modest overpotentials. The surface iron oxide/phosphate, which is formed in situ, is proposed to improve the HER activity by facilitating the water-dissociation step and serves directly as the catalytically-active component for the OER process.

Multiresidue analysis of 59 nonallowed substances and other contaminants in cosmetics.

A method was developed for the determination of 59 glucocorticoids, sex hormones, nonsteroidal anti-inflammatory drugs, antibiotics, and other contaminants in cosmetics simultaneously by ultra high performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry. Acetonitrile was used to extract the sample, and the mixed sorbents were dispersed for purification. With the optimal conditions, the optimized pretreatment processes led to no significant interference on analysis from an extremely complicated sample matrix, and the linear ranges of 59 analytes were 0-480.0 µg/kg with the correlation coefficients above 0.99 and the limits of quantification (S/N≥10) were 5-40 µg/kg. Statistical evaluation revealed that the average recoveries were in the range of 61.2-131.2%, and relative standard deviations were in the range of 2.0-22.8%, meanwhile the interday precision ranged from 3.8 to 21.8%. This method is simple, fast, and credible, and it can be applied to simultaneous screening and determination of various classes of substances under investigations illegally presented in cosmetic products, covering a wide diversity of polarities, and pKa values.

Oroxyloside protects against dextran sulfate sodium-induced colitis by inhibiting ER stress via PPARγ activation.

Ulcerative colitis (UC), a prevalent form of inflammatory bowel disease (IBD), may result from immune system dysfunction, leading to the sustained overproduction of reactive oxygen species (ROS) and subsequent cellular oxidative stress damage. Recent studies have identified both peroxisome proliferator-activated receptor-γ (PPARγ) and endoplasmic reticulum (ER) stress as critical targets for the treatment of IBD. Oroxyloside (C22H20O11), derived from the root of Scutellariabaicalensis Georgi, has traditionally been used in treating inflammatory diseases. In this study, we investigated the molecular mechanisms by which oroxyloside mitigates dextran sulfate sodium (DSS)-induced colitis. We examined the effects of oroxyloside on ROS-mediated ER stress in colitis, including the protein expressions of GRP78, p-PERK, p-eIF2α, ATF4, and CHOP, which are associated with ER stress. The beneficial impact of oroxyloside was reversed by the PPARγ antagonist GW9662 (1 mg·kg-1, i.v.) in vivo. Furthermore, oroxyloside decreased pro-inflammatory cytokines and ROS production in both bone marrow-derived macrophages (BMDM) and the mouse macrophage cell line RAW 264.7. However, PPARγ siRNA transfection blocked the anti-inflammatory effect of oroxyloside and even abolished ROS generation and ER stress activation inhibited by oroxyloside in vitro. In conclusion, our study demonstrates that oroxyloside ameliorates DSS-induced colitis by inhibiting ER stress via PPARγ activation, suggesting that oroxyloside might be a promising effective agent for IBD.

Bioinformatics-based analysis reveals elevated CYTL1 as a potential therapeutic target for BRAF-mutated melanoma.

Introduction: Despite many recent emerging therapeutic modalities that have prolonged the survival of melanoma patients, the prognosis of melanoma remains discouraging, and further understanding of the mechanisms underlying melanoma progression is needed. Melanoma patients often have multiple genetic mutations, with BRAF mutations being the most common. In this study, public databases were exploited to explore a potential therapeutic target for BRAF-mutated melanoma. Methods: In this study, we analyzed differentially expressed genes (DEGs) in normal tissues and melanomas, Braf wild-type and Braf mutant melanomas using information from TCGA databases and the GEO database. Subsequently, we analyzed the differential expression of CYTL1 in various tumor tissues and its effect on melanoma prognosis, and resolved the mutation status of CYTL1 and its related signalling pathways. By knocking down CYTL1 in melanoma cells, the effects of CYTL1 on melanoma cell proliferation, migration and invasion were further examined by CCK8 assay, Transwell assay and cell migration assay. Results: 24 overlapping genes were identified by analyzing DEGs common to melanoma and normal tissue, BRAF-mutated and BRAF wild-type melanoma. Among them, CYTL1 was highly expressed in melanoma, especially in BRAF-mutated melanoma, and the high expression of CYTL1 was associated with epithelial-mesenchymal transition (EMT), cell cycle, and cellular response to UV. In melanoma patients, especially BRAF-mutated melanoma patients, clinical studies showed a positive correlation between increased CYTL1 expression and shorter overall survival (OS) and disease-free survival (DFS). In vitro experiments further confirmed that the knockdown of CYTL1 significantly inhibited the migration and invasive ability of melanoma cells. Conclusion: CYTL1 is a valuable prognostic biomarker and a potentially effective therapeutic target in melanoma, especially BRAF-mutated melanoma.

Lysosomal membrane permeabilization mediated apoptosis involve in perphenazine-induced hepatotoxicity in vitro and in vivo.

Antipsychotic drugs represent a class of lysosomotropic drugs widely used in clinical practice. However, the hepatotoxicity of these drugs has been reported in recent years. Therefore, understanding the changes in cellular homeostasis mediated by these drugs is of great significance for revealing the true mechanisms underlying hepatotoxicity. Perphenazine is a classical antipsychotic drug that can reportedly induce extrapyramidal and sympatholytic side effects. The present research focuses on the toxicity effect of perphenazine on normal human hepatocytes. To assess the hepatotoxicity of continuous administration of perphenazine and investigate potential mechanisms related to apoptosis, human normal L02 hepatocytes were exposed to 10-40 µM perphenazine in vitro. The results showed that perphenazine inhibited cell viability in a concentration and time-dependent manner. Furthermore, 30 µM perphenazine induced intense lysosome vacuolation, impaired lysosomal membrane, and induced lysosomal membrane permeabilization (LMP), ultimately triggering lysosomal cell death in L02 cells. Knockdown cathepsin D(CTSD) also ameliorated perphenazine-induced liver injury via the inhibition of LMP. In vivo, ICR mice received intragastric administration of 10-180 mg/kg B.W. perphenazine every other day for 21 days. 180 mg/kg perphenazine significantly increased histological injury and aminotransferases compared with control. Taken together, our findings suggest that perphenazine can trigger hepatotoxicity through lysosome disruption both in vitro and in vivo.

Double layer capacitance of anode/solid-electrolyte interfaces.

The double layer of electrode/electrolyte interfaces plays a fundamental role in determining the performance of solid state electrochemical cells. The double layer capacitance is one of the most-studied descriptors of the double layer. This work examines a case study on lanthanum strontium vanadate (LSV)/yttria-stabilized zirconia (YSZ) interfaces exposed in solid oxide fuel cell anode environment. The apparent double layer capacitance is obtained from impedance spectroscopy. The intrinsic double layer capacitance is evaluated based on Stern's method in conjunction with the Volta potential analysis across LSV/YSZ interfaces. Both the apparent and the intrinsic double layer capacitances exhibit right-skewed volcano patterns, when the interfaces are subjected to anodic biases from 0 to 150 mV. The apparent double layer capacitance is about one order of magnitude larger than the intrinsic double layer capacitance. This discrepancy roots in the inconsistent surface areas that are involved. This analysis of capacitance would provide a more realistic TPB estimate of a working solid-state electrochemical device.

Image Mosaic Algorithm-Based Analysis of Pathological Characteristics of Gastric Polyp Patients Using Computed Tomography Images.

The application value of image mosaic algorithm (IMA) based CT imaging technology in the analysis of pathological characteristics of gastric polyp (GP) patients was explored in this work. 588 cases of GP patients in the hospital were selected as the research objects, and CT images based on IMA were adopted for examination. The patient's basic information, image performance, and gastroscopy results were recorded. The results showed that the absolute mean bright error (AMBE) index and information entropy of the IMA are 0.0625 and 7.0385, respectively. The clinical symptoms of patients were mostly abdominal pain (21.4%), abdominal distension (15.6%), and sour regurgitation (17.8%). The common size of GP was no more than 0.5 cm, and the common type was Yamada type II. There were notable differences between single and multiple GPs of different pathological types (P < 0.05). Proliferative polyps were mostly found in the stomach and antrum, while fundus gland polyps were mostly in the stomach and fundus. There was significant difference between the growth location of the hyperplastic polyp and basal gland polyp (P < 0.05). In summary, the CT images of IMA proposed in this paper can not only realize image splicing effectively but also were superior to the traditional SIFT method in the quality of splicing image and were conducive to the analysis of the pathological characteristics of GP patients, which had significant clinical promotion value.

High quality N-polar GaN films grown with varied V/III ratios by metal-organic vapor phase epitaxy.

We studied the growths and characterizations of N-polar GaN films grown with constant and varied V/III ratios in high-temperature (HT) GaN growth on offcut c-plane sapphire substrates by metal-organic vapor phase epitaxy. It is found that growth with a constantly low V/III ratio resulted in a high crystallinity but a rough surface and a high oxygen concentration, whereas growth with a high V/III ratio led to a smooth surface but a high carbon concentration and a degraded crystallinity. The overall quality of the N-polar GaN epilayer cannot be effectively improved simply by tuning the V/III ratio. The growth with varied V/III ratios was conducted by lowering the V/III ratio in the initial HT-GaN growth and keeping the V/III ratio constantly high in the subsequent growth. Such a change of V/III ratio resulted in a 3D-to-2D like growth mode transition during the early stage of HT-GaN growth which helped reduce threading dislocations and suppress impurity incorporation. By optimizing the nucleation temperature and the thickness of the initial low-V/III-ratio layer, the minimum full-widths at half-maximum of (002̄)/(102̄) rocking curves obtained were 288/350 arcsec and the oxygen concentration was reduced significantly from 1.6 × 1018 cm-3 to 3.7 × 1017 cm-3 while keeping a hillock-free smooth surface morphology. The overall quality of the N-polar GaN films was considerably improved. We believe that this simple, yet effective growth technique has great application prospects for high-performance N-polar GaN-based electron devices.

Highly Stretchable Fiber-Based Potentiometric Ion Sensors for Multichannel Real-Time Analysis of Human Sweat.

Wearable potentiometric ion sensors are attracting attention for real-time ion monitoring in biological fluids. One of the key challenges lies in keeping the analytical performances under a stretchable state. Herein, we report a highly stretchable fiber-based ion-selective electrode (ISE) prepared by coating an ion-selective membrane (ISM) on a stretchable gold fiber electrode. The fiber ISE ensures high stretchability up to 200% strain with only 2.1% increase in resistance of the fiber electrode. Owing to a strong attachment between the ISM and gold fiber electrode substrate, the ISE discloses favorable stability and potential repeatability. The Nernst slope of the ion response fluctuates from 59.2 to 57.4 mV/dec between 0 and 200% strain. Minor fluctuation of the intercept (E0) (±4.97 mV) also results. The ISE can endure 1000 cycles at the maximum stretch. Sodium, chloride, and pH fiber sensors were fabricated and integrated into a hairband for real-time analysis of human sweat. The result displays a high accuracy compared with ex situ analysis. The integrated sensors were calibrated before and just after on-body measurements, and they offer reliable results for sweat analysis.

Growth promotion of vertical graphene on SiO2/Si by Ar plasma process in plasma-enhanced chemical vapor deposition.

This study investigates the growth promotion of vertically oriented graphene in plasma-enhanced chemical vapor deposition through Ar plasma treatment. Combined with various substrate treatments, including hydrofluoric acid etching and oxidation after Ar plasma treatment, Ar plasma pretreatment promotes vertical growth through the microcavity on the rough substrate surface and the active growth sites. The microcavity affects the strain distribution and defects of as-deposited planar films, which benefit the transition of 2D deposition to 3D vertical growth. A growth model on the effect of Ar plasma pretreatment is proposed.

Edge morphology evolution of graphene domains during chemical vapor deposition cooling revealed through hydrogen etching.

During cooling, considerable changes such as wrinkle formation and edge passivation occur in graphene synthesized on the Cu substrate. Wrinkle formation is caused by the difference in the thermal expansion coefficients of graphene and its substrate. This work emphasizes the cooling-induced edge passivation. The graphene-edge passivation can limit the regrowth of graphene at the domain edge. Our work shows that silicon-containing particles tend to accumulate at the graphene edge, and the formation of these particles is related to cooling. Furthermore, a clear curvature can be observed at the graphene edge on the Cu substrate, indicating the sinking of the graphene edge into the Cu substrate. Both the sinking of the graphene edge and the accumulation of silicon-containing particles are responsible for edge passivation. In addition, two kinds of graphene edge morphologies are observed after etching, which were explained by different etching mechanisms that illustrate the changes of the graphene edge during cooling.

Mussel-inspired one-pot synthesis of transition metal and nitrogen co-doped carbon (M/N-C) as efficient oxygen catalysts for Zn-air batteries.

Transition metal and nitrogen co-doping into carbon is an effective approach to promote the catalytic activities towards the oxygen reduction reaction (ORR) and/or oxygen evolution reaction (OER) in the resultant electrocatalysts, M/N-C. The preparation of such catalysts, however, is often complicated and in low yield. Herein we report a robust approach for easy synthesis of M/N-C hybrids in high yield, which includes a mussel-inspired polymerization reaction at room temperature and a subsequent carbonization process. With the introduction of selected transition metal salts into an aqueous solution of dopamine (DA), the obtained mixture self-polymerizes to form metal-containing polydopamine (M-PDA) composites, e.g. Co-PDA, Ni-PDA and Fe-PDA. Upon carbonization at elevated temperatures, these metal-containing composites were converted into M/N-C, i.e. Co-PDA-C, Ni-PDA-C and Fe-PDA-C, respectively, whose morphologies, chemical compositions, and electrochemical performances were fully studied. Enhanced ORR activities were found in all the obtained hybrids, with Co-PDA-C standing out as the most promising catalyst with excellent stability and catalytic activities towards both ORR and OER. This was further proven in Zn-air batteries (ZnABs) in terms of discharge voltage stability and cycling performance. At a discharge-charge current density of 2 mA cm(-2) and 1 h per cycle, the Co-PDA-C based ZnABs were able to steadily cycle up to 500 cycles with only a small increase in the discharge-charge voltage gap which notably outperformed Pt/C; at a discharge current density of 5 mA cm(-2), the battery continuously discharged for more than 540 h with the discharge voltage above 1 V and a voltage drop rate of merely 0.37 mV h(-1). With the simplicity and scalability of the synthetic approach and remarkable battery performances, the Co-PDA-C hybrid catalyst is anticipated to play an important role in practical ZnABs.