MXene nanosheet-derived N, S-codoped graphene quantum dots for ultrasensitive and selective detection of 3-nitro-l-tyrosine in human serum.

3-Nitro-l-tyrosine (3NT) is an oxidative stress metabolite associated with neurodegenerative diseases such as Parkinson's disease and rheumatoid arthritis. In this study, the N, S-co-doped graphene quantum dots (NSGQDs) derived from nitrogen-doped Ti3C2Tx MXene nanosheet via the hydrothermal method in the presence of mercaptosuccinic acid was synthesized as an optical sensing probe to detect 3NT in human serum. Tetramethyl ammonium hydroxide, the nitrogen source and delamination agent, was used to prepare nitrogen-doped MXene nanosheets via one step at room temperature. The as-prepared NSGQDs are uniform with an average size of 1.2 ± 0.6 nm, and can be stable in aqueous solution for at least 90 d to serve as the fluorescence probe. The N atoms in N-MXene reduce the restacking and aggregation of MXene nanosheets, while the sulfur dopant in NSGQDs increases the quantum yield from 6.2 to 12.1 % as well as enhances the selectivity of 3NT over the other 12 interferences via coordination interaction with nitro group in 3NT. A linear range of 0.02-150 µM in PBS and 0.05-200 µM in human serum with a recovery of 97-108 % for 3NT detection is observed. Moreover, the limit of detection can be lowered to 4.2 and 7 nM in PBS and 1 × diluted human serum, respectively. Results obtained clearly indicate the potential application of the N-Ti3C2Tx derived NSGQD for effective detection of 3NT, which can open a window for the synthesis of doped GQDs via 2D MXene materials for ultrasensitive and selective detection of other biometabolites and biomarkers of neurodegenerative diseases in biological fluids.

Understanding Structure-Activity Relationship in Pt-loaded g-C3 N4 for Efficient Solar- Photoreforming of Polyethylene Terephthalate Plastic and Hydrogen Production.

Coupling the hydrogen evolution reaction with plastic waste photoreforming provides a synergistic path for simultaneous production of green hydrogen and recycling of post-consumer products, two major enablers for establishment of a circular economy. Graphitic carbon nitride (g-C3 N4 ) is a promising photocatalyst due to its suitable optoelectronic and physicochemical properties, and inexpensive fabrication. Herein, a mechanistic investigation of the structure-activity relationship of g-C3 N4 for poly(ethylene terephthalate) (PET) photoreforming is reported by carefully controlling its fabrication from a subset of earth-abundant precursors, such as dicyandiamide, melamine, urea, and thiourea. These findings reveal that melamine-derived g-C3 N4 with 3 wt.% Pt has significantly higher performance than alternative derivations, achieving a maximum hydrogen evolution rate of 7.33 mmolH2  gcat -1  h-1 , and simultaneously photoconverting PET into valuable organic products including formate, glyoxal, and acetate, with excellent stability for over 30 h of continuous production. This is attributed to the higher crystallinity and associated chemical resistance of melamine-derived g-C3 N4 , playing a major role in stabilization of its morphology and surface properties. These new insights on the role of precursors and structural properties in dictating the photoactivity of g-C3 N4 set the foundation for the further development of photocatalytic processes for combined green hydrogen production and plastic waste reforming.

Optimal Coatings of Co3 O4 Anodes for Acidic Water Electrooxidation.

Implementation of proton-exchange membrane water electrolyzers for large-scale sustainable hydrogen production requires the replacement of scarce noble-metal anode electrocatalysts with low-cost alternatives. However, such earth-abundant materials often exhibit inadequate stability and/or catalytic activity at low pH, especially at high rates of the anodic oxygen evolution reaction (OER). Here, the authors explore the influence of a dielectric nanoscale-thin oxide layer, namely Al2 O3 , SiO2 , TiO2 , SnO2 , and HfO2 , prepared by atomic layer deposition, on the stability and catalytic activity of low-cost and active but insufficiently stable Co3 O4 anodes. It is demonstrated that the ALD layers improve both the stability and activity of Co3 O4 following the order of HfO2 > SnO2 > TiO2 > Al2 O3 , SiO2 . An optimal HfO2 layer thickness of 12 nm enhances the Co3 O4 anode durability by more than threefold, achieving over 42 h of continuous electrolysis at 10 mA cm-2 in 1 m H2 SO4 electrolyte. Density functional theory is used to investigate the superior performance of HfO2 , revealing a major role of the HfO2 |Co3 O4 interlayer forces in the stabilization mechanism. These insights offer a potential strategy to engineer earth-abundant materials for low-pH OER catalysts with improved performance from earth-abundant materials for efficient hydrogen production.

Understanding the Role of (W, Mo, Sb) Dopants in the Catalyst Evolution and Activity Enhancement of Co3 O4 during Water Electrolysis via In Situ Spectroelectrochemical Techniques.

Unlocking the potential of the hydrogen economy is dependent on achieving green hydrogen (H2 ) production at competitive costs. Engineering highly active and durable catalysts for both oxygen and hydrogen evolution reactions (OER and HER) from earth-abundant elements is key to decreasing costs of electrolysis, a carbon-free route for H2 production. Here, a scalable strategy to prepare doped cobalt oxide (Co3 O4 ) electrocatalysts with ultralow loading, disclosing the role of tungsten (W), molybdenum (Mo), and antimony (Sb) dopants in enhancing OER/HER activity in alkaline conditions, is reported. In situ Raman and X-ray absorption spectroscopies, and electrochemical measurements demonstrate that the dopants do not alter the reaction mechanisms but increase the bulk conductivity and density of redox active sites. As a result, the W-doped Co3 O4 electrode requires ≈390 and ≈560 mV overpotentials to reach ±10 and ±100 mA cm-2 for OER and HER, respectively, over long-term electrolysis. Furthermore, optimal Mo-doping leads to the highest OER and HER activities of 8524 and 634 A g-1 at overpotentials of 0.67 and 0.45 V, respectively. These novel insights provide directions for the effective engineering of Co3 O4 as a low-cost material for green hydrogen electrocatalysis at large scales.

Solvent Etching Process for Graphitic Carbon Nitride Photocatalysts Containing Platinum Cocatalyst: Effects of Water Hydrolysis on Photocatalytic Properties and Hydrogen Evolution Behaviors.

In this study, we synthesized Pt/g-C3N4 photocatalysts modified by a solvent etching process where ethanol (Pt/CN0), water (Pt/CN100), and a 50:50 mixture (Pt/CN50) were used as a solvent, and investigated the optimal properties of g-C3N4 to prepare the best Pt/g-C3N4 for photocatalytic hydrogen evolution. From diverse characterizations, water was proven to be a stronger solvent agent, resulting in not only the introduction of more O-functional groups onto the g-C3N4 surface, but also the degradation of a regular array of tri-s-triazine units in the g-C3N4 structure. While the addition of O-functional groups positively influenced the oxidation state of the Pt cocatalyst and the hydrogen production rate, the changes to g-C3N4 structure retarded charge transfer on its surface, inducing negative effects such as fast recombination and less oxidized Pt species. Pt/CN50 that was synthesized with the 50:50 solvent mixture exhibited the highest hydrogen production rate of 590.9 µmol g-1h-1, while the hydrogen production rates of Pt/CN0 (with pure ethanol solvent) and Pt/CN100 (with pure water solvent) were 462.7, and 367.3 µmol g-1h-1, respectively.

Ethanol Solvothermal Treatment on Graphitic Carbon Nitride Materials for Enhancing Photocatalytic Hydrogen Evolution Performance.

Recently, Pt-loaded graphic carbon nitride (g-C3N4) materials have attracted great attention as a photocatalyst for hydrogen evolution from water. The simple surface modification of g-C3N4 by hydrothermal methods improves photocatalytic performance. In this study, ethanol is used as a solvothermal solvent to modify the surface properties of g-C3N4 for the first time. The g-C3N4 is thermally treated in ethanol at different temperatures (T = 140 °C, 160 °C, 180 °C, and 220 °C), and the Pt co-catalyst is subsequently deposited on the g-C3N4 via a photodeposition method. Elemental analysis and XPS O 1s data confirm that the ethanol solvothermal treatment increased the contents of the oxygen-containing functional groups on the g-C3N4 and were proportional to the treatment temperatures. However, the XPS Pt 4f data show that the Pt2+/Pt0 value for the Pt/g-C3N4 treated at ethanol solvothermal temperature of 160 °C (Pt/CN-160) is the highest at 7.03, implying the highest hydrogen production rate of Pt/CN-160 is at 492.3 µmol g-1 h-1 because the PtO phase is favorable for the water adsorption and hydrogen desorption in the hydrogen evolution process. In addition, the electrochemical impedance spectroscopy data and the photoluminescence spectra emission peak intensify reflect that the Pt/CN-160 had a more efficient charge separation process that also enhanced the photocatalytic activity.

Antenatal dexamethasone use and respiratory distress in late preterm infants: results from first Vietnamese matched cohort study.

BACKGROUND: Respiratory distress syndrome (RDS) is one of the leading causes of early neonatal morbidity and mortality in late preterm infants (LPIs) worldwide. This matched cohort study aimed to assess how the antenatal dexamethasone use affect the respiratory distress (RD) proportion in preterm newborns between 34 0/7 weeks and 36 6/7 weeks of gestation. METHODS: This was a prospective cohort study on 78 women with singleton pregnancy who were in threatened preterm birth and had not received prior dexamethasone, who were admitted between 34 0/7 weeks and 36 6/7 weeks at Hue University of Medicine and Pharmacy Hospital from June 2018 to May 2020. The matched control group without dexamethasone use included 78 pregnant women diagnosed with threatened late preterm births who were at similar gestational ages and estimated fetal weights as the treatment group. The treatment group received 6 mg intramuscular dexamethasone every 12 h for a total of 4 doses or until delivery. Primary outcome was the rate of neonatal RD. Secondary neonatal outcomes included the need for respiratory support, neonatal intensive care unit (NICU) admission, hypoglycemia, necrotizing enterocolitis, intraventricular hemorrhage, and neonatal death. Statistical analyses were performed by using SPSS software, version 26.0. RESULTS: The proportion of RD in LPI was significantly lower in the treatment group than in the matched control group (10.3% vs. 23.1%, respectively), adjusted Odds Ratio [aOR] 0.29; 95% confidence interval [CI] 0.10 - 0.83 and p = 0.021. Neonatal hypoglycemia was more common in the dexamethasone group than in the matched group (25.6% vs. 12.8%, respectively; aOR, 2.59; 95% CI, 1.06 - 6.33; p = 0.037). There were no significant between-groups differences in the incidence of respiratory support, NICU admission or length of hospital stay. CONCLUSIONS: Administration of antenatal dexamethasone to women at risk for late preterm birth could help to lower the proportion of respiratory distress in late preterm infants.

Expression patterns of bovine CD1 in vivo and assessment of the specificities of the anti-bovine CD1 antibodies.

Research addressing the in vivo effects of T cell activation by lipids, glycolipids, and lipopeptides is hampered by the absence of a suitable animal model. Mice and rats do not express CD1a, CD1b, and CD1c molecules that present pathogen-derived lipid antigens in humans. In cattle, two CD1A and three CD1B genes are transcribed. The proteins encoded by these genes differ in their antigen binding domains and in their cytoplasmic tails, suggesting that they may traffic differently in the cell and thus have access to different antigens. In the current study, we describe the genomic organization of the bovine CD1 locus and transcription of bovine CD1 genes in freshly isolated dendritic cells and B cells from different tissues. After determining the specificity of previously only partly characterized anti-CD1 antibodies by testing recombinant single chain bovine CD1 proteins and CD1-transfected cells, we were able to determine cell surface protein expression on freshly isolated cells. Our study suggests that CD1b1 and CD1b3 are more broadly expressed than CD1b5, and CD1a2 is more broadly expressed than CD1a1. Pseudoafferent lymph dendritic cells express CD1B genes, but no transcription is detected in lymph nodes. Even though B cells transcribe CD1B genes, there is no evidence of protein expression at the cell surface. Thus, patterns of CD1 protein expression are largely conserved among species.

Early host response in the mammary gland after experimental Streptococcus uberis challenge in heifers.

Streptococcus uberis is a highly prevalent causative agent of bovine mastitis, which leads to large economic losses in the dairy industry. The aim of this study was to examine the host response during acute inflammation after experimental challenge with capsulated Strep. uberis. Gene expression in response to Strep. uberis was compared between infected and control quarters in 3 animals. All quarters (n=16) were sampled at 16 different locations. Microarray data showed that 239 genes were differentially expressed between infected and control quarters. No differences in gene expression were observed between the different locations. Microarray data were confirmed for several genes using quantitative PCR analysis. Genes differentially expressed due to early Strep. uberis mastitis represented several stages of the process of infection: (1) pathogen recognition; (2) chemoattraction of neutrophils; (3) tissue repair mechanisms; and (4) bactericidal activity. Three different pathogen recognition genes were induced: ficolins, lipopolysaccharide binding protein, and toll-like receptor 2. Calgranulins were found to be the most strongly upregulated genes during early inflammation. By histology and immunohistochemistry, we demonstrated that changes in gene expression in response to Strep. uberis were induced both in infiltrating somatic milk cells and in mammary epithelial cells, demonstrating that the latter cell type plays a role in milk production as well as immune responsiveness. Given the rapid development of inflammation or mastitis after infection, early diagnosis of (Strep. uberis) mastitis is required for prevention of disease and spread of the pathogen. Insight into host responses could help to design immunomodulatory therapies to dampen inflammation after (early) diagnosis of Strep. uberis mastitis. Future research should focus on development of these early diagnostics and immunomodulatory components for mastitis treatment.

The bovine CD1D gene has an unusual gene structure and is expressed but cannot present α-galactosylceramide with a C26 fatty acid.

Although CD1d and NKT cells have been proposed to have highly conserved functions in mammals, data on functions of CD1d and NKT cells in species other than humans and rodents are lacking. Upon stimulation with the CD1d-presented synthetic antigen α-galactosylceramide, human and rodent type I invariant NKT cells release large amounts of cytokines. The two bovine CD1D (boCD1D) genes have structural features that suggest that they cannot be translated into functional proteins expressed on the cell surface. Here we provide evidence that despite an intron-exon structure and signal peptide that are different from all other known CD1 genes, boCD1D can be translated into a protein that is expressed on the cell surface. However, in vivo treatment of cattle (Bos taurus) with 0.1, 1, or 10 µg kg⁻¹ of the most commonly used α-galactosylceramide, which has a C26 fatty acid, did not lead to an increase in body temperature and serum cytokine levels of the animals. This lack of reactivity is not due to a complete inability of boCD1d to present glycosphingolipids because α-galactosylceramide variants with shorter fatty acids could be presented by boCD1d to human NKT cells in vitro. This suggests that the natural ligands of boCD1d are smaller lipids.

Immune response of cattle immunized with a conjugate of the glycolipid glucose monomycolate and protein.

Strong anti glycolipid IgG responses can occur in humans and animals, but contrary to anti protein responses and anti glycoprotein responses, the exact mechanism of induction is unknown. We have previously shown that experimental immunization with the glycolipid glucose monomycolate (GMM) causes the development of specific T cell responses, but not of anti GMM antibodies. However, cattle naturally infected with Mycobacterium avium ssp. paratuberculosis produce high levels of anti GMM IgG. In the present study, we tested whether vaccination with GMM conjugated to a protein mimics natural infection in its capacity to induce the production of antibodies against GMM. Cattle were immunized (n=5 per group) with GMM conjugated to a protein, or GMM and protein non-conjugated and administered at contralateral locations, or carrier only. Although immunization with the GMM-protein conjugate vaccine and the non-conjugated vaccine induced protein specific antibody responses, GMM specific antibodies were not detected in either of the groups. In conclusion, the generation of isotype-switched anti lipid antibodies appears to require more than providing peptide epitopes for T helper cells to support glycolipid specific B cells in antibody production.

Low cross-reactivity of T-cell responses against lipids from Mycobacterium bovis and M. avium paratuberculosis during natural infection.

Although CD1 proteins are known to present mycobacterial lipid antigens to T cells, there is little understanding of the in vivo behavior of T cells restricted by CD1a, CD1b and CD1c, and the relative immunogenicity and immunodominance of individual lipids within the total array of lipids that comprise a bacterium. Because bovines express multiple CD1 proteins and are natural hosts of Mycobacterium bovis and Mycobacterium avium paratuberculosis (MAP), we used them as a new animal model of CD1 function. Here, we report the surprisingly divergent responses against lipids produced by these two pathogens during infection. Despite considerable overlap in lipid content, only three out of 69 animals cross-react with M. bovis and MAP total lipid preparations. The unidentified immunodominant compound of M. bovis is a hydrophilic compound, whereas the immunodominant lipid of MAP is presented by CD1b and was identified as glucose monomycolate (GMM). The preferential recognition of GMM antigen by MAP-infected cattle may be explained by the higher expression of GMM by MAP than by M. bovis. The bacterial species-specific nature of the CD1-restricted, adaptive T-cell response affects the approach to development of lipid based immunodiagnostic tests.

The mycobacterial glycolipid glucose monomycolate induces a memory T cell response comparable to a model protein antigen and no B cell response upon experimental vaccination of cattle.

Glycolipids are presented to T cells by human group 1 CD1 proteins, but are not used as subunit vaccines yet. Experimental immunizations with pure mycobacterial glucose monomycolate (GMM) and keyhole limpet haemocyanin (KLH) in cattle, a species which, unlike mice, expresses group 1 CD1, showed that GMM was equally efficient as KLH in generating T cell responses in blood, but not in the draining lymph node. Also, KLH induced strong antibody responses whereas GMM did not. These data suggest that non-overlapping T cell populations are targeted and demonstrate the potential of glycolipids as a special class of subunit vaccine candidates.