A general route via formamide condensation to prepare atomically dispersed metal-nitrogen-carbon electrocatalysts for energy technologies

Single-atom electrocatalysts (SAECs) have gained tremendous attention due to their unique active sites and strong metal–substrate interactions. However, the current synthesis of SAECs mostly relies on costly precursors and rigid synthetic conditions and often results in very low content of single-site metal atoms. Herein, we report an efficient synthesis method to prepare metal–nitrogen–carbon SAECs based on formamide condensation and carbonization, featuring a cost-effective general methodology for the mass production of SAECs with high loading of atomically dispersed metal sites. The products with metal inclusion were termed as formamide-converted metal–nitrogen–carbon (shortened as f-MNC) materials. Seven types of single-metallic f-MNC (Fe, Co, Ni, Mn, Zn, Mo and Ir), two bi-metallic (ZnFe and ZnCo) and one tri-metallic (ZnFeCo) SAECs were synthesized to demonstrate the generality of the methodology developed. Remarkably, these f-MNC SAECs can be coated onto various supports with an ultrathin layer as pyrolysis-free electrocatalysts, among which the carbon nanotube-supported f-FeNC and f-NiNC SAECs showed high performance for the O2 reduction reaction (ORR) and the CO2 reduction reaction (CO2RR), respectively. Furthermore, the pyrolysis products of supported f-MNC can still render isolated metallic sites with excellent activity, as exemplified by the bi-metallic f-FeCoNC SAEC, which exhibited outstanding ORR performance in both alkaline and acid electrolytes by delivering ∼70 and ∼20 mV higher half-wave potentials than that of commercial 20 wt% Pt/C, respectively. This work offers a feasible approach to design and manufacture SAECs with tuneable atomic metal components and high density of single-site metal loading, and thus may accelerate the deployment of SAECs for various energy technology applications

Results of quality assessment by Cochrane risk of bias.

<p>a. each risk of bias item presented as percentages across all included studies. b. each risk of bias item for each included study.</p

Changes in the heterogeneity of abdominal pain VAS score at 24h post-procedure after sequential exclusion of one study at a time.

<p>Changes in the heterogeneity of abdominal pain VAS score at 24h post-procedure after sequential exclusion of one study at a time.</p

Characteristics of the included studies.

<p>Characteristics of the included studies.</p

Flow diagram of studies identified, included, and excluded.

<p>Flow diagram of studies identified, included, and excluded.</p

CO₂ insufflation versus air insufflation for endoscopic submucosal dissection: A meta-analysis of randomized controlled trials

<div><p>Background</p><p>Carbon dioxide (CO₂) insufflation is increasingly used for endoscopic submucosal dissection (ESD) owing to the faster absorption of CO₂ as compared to that of air. Studies comparing CO₂ insufflation and air insufflation have reported conflicting results.</p><p>Objectives</p><p>This meta-analysis is aimed to assess the efficacy and safety of use of CO₂ insufflation for ESD.</p><p>Methods</p><p>Clinical trials of CO₂ insufflation versus air insufflation for ESD were searched in PubMed, Embase, the Cochrane Library and Chinese Biomedical Literature Database. We performed a meta-analysis of all randomized controlled trials (RCTs).</p><p>Results</p><p>Eleven studies which compared the use of CO₂ insufflation and air insufflation, with a combined study population of 1026 patients, were included in the meta-analysis (n = 506 for CO₂ insufflation; n = 522 for air insufflation). Abdominal pain and VAS scores at 6h and 24h post-procedure in the CO₂ insufflation group were significantly lower than those in the air insufflation group, but not at 1h and 3h after ESD. The percentage of patients who experienced pain 1h and 24h post-procedure was obviously decreased. Use of CO₂ insufflation was associated with lower VAS scores for abdominal distention at 1h after ESD, but not at 24h after ESD. However, no significant differences were observed with respect to postoperative transcutaneous partial pressure carbon dioxide (PtcCO₂), arterial blood carbon dioxide partial pressure (PaCO₂), oxygen saturation (SpO₂%), abdominal circumference, hospital stay, white blood cell (WBC) counts, C-Reactive protein (CRP) level, dosage of sedatives used, incidence of dysphagia and other complications.</p><p>Conclusion</p><p>Use of CO₂ insufflation for ESD was safe and effective with regard to abdominal discomfort, procedure time, and the residual gas volume. However, there appeared no significant differences with respect to other parameters namely, PtcCO₂, PaCO₂, SpO₂%, abdominal circumference, hospital stay, sedation dosage, complications, WBC, CRP, and dysphagia.</p></div

Forest plot of primary outcomes of ESD with CO₂ insufflation and air insufflation.

<p>A: post-procedural abdominal pain VAS score; SMD with 95% CI; B: Percentage of patients without pain; RR with 95% CI; C: mean PtcCO₂ levels; SMD with 95% CI; D: post-procedural PaCO₂; SMD with 95% CI.</p

Effects of miR-204 expression on cell proliferation.

<p>(A) Cells transfected with miR-204 inhibitor and viabilities were determined with CCK-8 assay. (B) Cells transfected with miR-204 mimics and viabilities were determined with CCK-8 assay. (C) Effects of miR-204 mimics or inhibitor on cell cycle of gastric cancer cells by flow cytometry. (D) Colony assay after cells transfected with miR-204 mimics and inhibitor. (*p<0.05).</p

MiR-204 is down-regulated in H. Pylori positive patients.

<p>(A) The expression levels of miR-204 in human H. Pylori positive tissues and normal tissues relative to U6 were determined by qRT-PCR. (B) The expression levels of miR-204 in H. pylori positive and negative tumor tissues. (C) The expression levels of miR-204 in CG,CAG and dysplasia in H. pylori positive tissues and H. pylori negative tissue. (D) The expression levels of miR-204 in H. pylori infected cells. (*p<0.05).</p

Decreased miR-204 in H. pylori-Associated Gastric Cancer Promotes Cancer Cell Proliferation and Invasion by Targeting SOX4

<div><p>Background</p><p>The molecular mechanism between Helicobacter pylori (H. pylori) infection and gastric cancer remained largely unknown. In this study, we determined the role of miRNA in H. pylori induced gastric cancer.</p><p>Methods and Results</p><p>We found that miR-204 was decreased in H. pylori positive tissues by qRT-PCR. Knockdown of miR-204 enhanced the invasion and proliferation ability of gastric cancer cells in vitro. Luciferase assay revealed that SOX4 was target gene of miR-204, which was found up-regulated in H. pylori positive tissues. Down-regulation of miR-204 and over-expression of SOX4 promoted epithelial-mesenchymal transition process.</p><p>Conclusion</p><p>Taken together, our findings demonstrated that miR-204 may act as a tumor suppressor in H. pylori induced gastric cancer by targeting SOX4.</p></div