Cr-doped BiYO3 photocatalyst for degradation of oxytetracycline under visible light irradiation

Hernández-Arellano Diana L.,Durán-Álvarez Juan C.,Cortés-Lagunes Silvana,Zanella Rodolfo,Soto Tania E.,López-Juárez Rigoberto 한국세라믹학회 2023 한국세라믹학회지 Vol.60 No.1

Chromium-doped BiYO3 powders were synthesized by the Pechini method at low temperature between 400 and 800 °C for 1 h. From the XRD results it was observed the coexistence between tetragonal and cubic phases for samples calcined at 400 °C for 1 h. Meanwhile, for samples calcined at 600 and 800 °C, a single cubic phase was observed. The powders consisted of agglomerates of nanocrystals as shown in the SEM and TEM images. The specific surface area was in the order of 3.01–7.74 m2 g−1, obtained from BET analysis. The band gap of BiYO3 and Cr-doped BiYO3 was < 2.21 eV which corroborates that these materials absorb light in the visible region of the electromagnetic spectrum. The photocatalytic decomposition of oxytetracycline was successfully achieved using Cr-doped BiYO3, where the best performance was obtained with BiY0.98Cr0.02O3 ceramic powders calcined at 800 °C for 1 h. For this composition the removal of oxytetracycline after 240 min of visible light irradiation was 100% of degradation and 75% of mineralization. The photocatalytic process was driven by the photo-holes, as a negligible production of ·OH radicals was observed in tests using scavengers. The photocatalytic activity of the BiY0.995Cr0.005O3 and BiY0.98Cr0.02O3 materials was corroborated under more realistic conditions, using tap water and trace concentration of the antibiotic. The high stability of the photocatalyst was observed through four consecutive reaction cycles. The results demonstrate that the Cr-doping has clearly improved the catalytic performance of BiYO3 for degradation of oxytetracycline under visible light irradiation.

Multiresistant Tuberculosis and Its Paradoxical Manifestations

José Luis Soto-Hernández 대한감염학회 2016 Infection and Chemotherapy Vol.48 No.3

Challenges managing COVID vaccine-induced immune thrombotic thrombocytopenia in low-middle income countries

Céleo Ramírez,Ramón Jeremías Soto Hernández,Reyna M. Durón 대한백신학회 2021 Clinical and Experimental Vaccine Research Vol.10 No.3

Vaccine-induced immune thrombotic thrombocytopenia (VITT) is an extremely rare complication associated with the adenovirus-vectored coronavirus disease 2019 (COVID-19) ChAdOx1 nCoV-19 (AZD1222) vaccine. It is characterized by venous thrombosis, mainly cerebral venous sinus thrombosis, moderate to severe thrombocytopenia, and rarely, thrombosis in cerebral arteries. This syndrome is similar to the heparin-induced thrombocytopenia and presents mostly among women aged 18–55 years, without previous exposure to heparin, usually 5 to 20 days after vaccination. However, cases have been reported in men and older adults [1-4]. Unlike COVID-19, this adverse effect might not represent a public health problem in itself, but it is already causing vaccine hesitancy in population groups susceptible to severe COVID-19, and poses a challenge in low resource settings [5]. The first case reports showed evidence that VITT has a mortality around 40% [1-3]. So far, cases have been reported and treated in hospitals of highly developed countries with first-rate health systems that facilitate early detection and treatment of this severe adverse event. VITT is confirmed by using PF4-dependent enzyme-linked immunosorbent assay (ELISA) assay, which allows the differential diagnosis from other causes of thrombosis in patients with a history of ChAdOx1 nCoV-19 vaccination in previous days. However, it is likely that a large number of hospitals in many low-middle income countries do not have approved PF4-dependent ELISA assays for accurate diagnosis, nor immunoglobulins, glucocorticoids, and non-heparin anticoagulants needed for the treatment of this condition [1-4]. In times of this COVID-19 pandemic and precision medicine, problems and solutions should be considered global. Policies related to COVID-19 need to be addressed considering varied public health and socioeconomic contexts. The ChAdOx1 nCoV-19 vaccine is one of the most used vaccines in low-middle income countries, where special testing to confirm VITT is not widely available. Therefore, real figures are unknown, and underreporting of this adverse effect should be considered. Patient information, government, and hospital preparedness in these countries are needed to diagnose and manage VITT adequately, and to reduce morbidity and mortality from this complication. These strategies will have a positive impact on public acceptance and adherence to COVID vaccination.

Fluid-structure interaction of a tensile fabric structure subjected to different wind speeds

Jesús G. Valdés-Vázquez,Adrián D. García-Soto,Alejandro Hernández-Martínez,José L. Nava 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.6

Despite the current technologic developments, failures in existent tensile fabric structures (TFS) subjected to wind do happen. However, design pressure coefficients are only obtained for large projects. Moreover, studies on TFSs with realistic supporting frames, comparing static and dynamic analyses and discussing the design implications, are lacking. In this study, fluid-Structure analyses of a TFS supported by masts and inclined cables, by subjecting it to different wind speeds, are carried out, to gain more understanding in the above-referred aspects. Wind-induced stresses in the fabric and axial forces in masts and cables are assessed for a hypar by using computational fluid dynamics. Comparisons are carried out versus an equivalent static analysis and also versus loadings deemed representative for design. The procedure includes the so-called form-finding, a finite element formulation for the TFS and the fluid formulation. The selected structure is deemed realistic, since the supporting frame is included and the shape and geometry of the TFS are not uncommon. It is found that by carrying out an equivalent static analysis with the determined pressure coefficients, differences of up to 24% for stresses in the fabric, 5.4% for the compressive force in the masts and 21% for the tensile force in the cables are found with respect to results of the dynamic analysis. If wind loads commonly considered for design are used, significant differences are also found, specially for the reactions at the supporting frame. The results in this study can be used as an aid by designers and researchers.

Production and characterization of Al2O3-Cu composite materials

Enrique Rocha-Rangel,José G. Miranda-Hernández,Socorro Moreno-Guerrero,Ana B. Soto-Guzmán 한양대학교 세라믹연구소 2006 Journal of Ceramic Processing Research Vol.7 No.4

Using an intense powder mixture of Al2O3 with different copper contents (1, 5, 10, 20 or 30 mass %) several Al2O3-Cu composite materials were fabricated. The microstructure of the composites was observed by optical and scanning electron microscopy. The observations show a microstructure formed by an Al2O3 ceramic matrix with fine Cu metallic networks. Due to the liquid sintering mechanism, the relative density reached by the samples was higher than 95%, this together with the fine and homogeneous microstructure present in the samples let us obtain composite materials with good values of toughness, hardness, elastic modulus and electrical properties. The incorporation of a ductile metal inside a hard ceramic matrix increments its toughness. The probable toughening mechanism is crack bridging due to the presence of a homogeneous ductile metal networks in the material’s microstructure. The values of density, hardness, elastic modulus and electrical resistance of the composites are directly dependent on the copper content in the matrix, because with an increase in copper content the density of the composites is larger, whereas, the hardness, elastic modulus and electrical resistance are reduced. Using an intense powder mixture of Al2O3 with different copper contents (1, 5, 10, 20 or 30 mass %) several Al2O3-Cu composite materials were fabricated. The microstructure of the composites was observed by optical and scanning electron microscopy. The observations show a microstructure formed by an Al2O3 ceramic matrix with fine Cu metallic networks. Due to the liquid sintering mechanism, the relative density reached by the samples was higher than 95%, this together with the fine and homogeneous microstructure present in the samples let us obtain composite materials with good values of toughness, hardness, elastic modulus and electrical properties. The incorporation of a ductile metal inside a hard ceramic matrix increments its toughness. The probable toughening mechanism is crack bridging due to the presence of a homogeneous ductile metal networks in the material’s microstructure. The values of density, hardness, elastic modulus and electrical resistance of the composites are directly dependent on the copper content in the matrix, because with an increase in copper content the density of the composites is larger, whereas, the hardness, elastic modulus and electrical resistance are reduced.

Antivirulence Activity of a Dietary Phytochemical: Hibiscus Acid Isolated from Hibiscus sabdariffa L. Reduces the Virulence of Pseudomonas aeruginosa in a Mouse Infection Model

Humberto Cortes-López,Javier Castro-Rosas,Rodolfo García-Contreras,José Salud Rodríguez-Zavala,Bertha González-Pedrajo,Miguel Díaz-Guerrero,Javier Hernández-Morales,Naybi Muñoz-Cazares,Marcos Soto-Her 한국식품영양과학회 2021 Journal of medicinal food Vol.24 No.9

Hibiscus sabdariffa L. (Hs) calyxes, rich in organic acids, are included in diets in different countries. In recent years, some phytochemicals have been shown to reduce bacterial virulence at sublethal concentrations by interfering with quorum sensing (QS) systems. Therefore, in this study the antivirulence properties of Hs calyxes and two γ-lactones (hibiscus acid [HA] and its methyl ester) in Pseudomonas aeruginosa were analyzed. Acetone and methanol extracts of Hs showed anti-QS activity by inhibiting violacein production (60% to 80% with 250 μg/mL). In molecular docking analysis, the γ-lactones registered a good binding score, which suggests strong interaction with the active site of LasR protein. To verify their effect in vitro, they were isolated from Hs and evaluated in six QS-regulated phenotypes, as well as in ExoU toxin that is released by the type III secretion system (T3SS). At 500 μg/mL they reduced alkaline protease (29–52%) and elastase (15–37%) activity, biofilm formation (∼75%), and swarming (50%), but there was no effect on pyocyanin production, hemolytic activity, or type III secretion. In a mouse abscess/necrosis model, HA at sublethal concentrations (15 and 31.2 μg/mL) affected infection establishment and prevented damage and systemic spread. In conclusion, HA is the first molecule identified with antivirulence properties in Hs with the potential to prevent infections caused by P. aeruginosa.

Direct and Indirect Targeting of PP2A by Conserved Bacterial Type-III Effector Proteins

Jin, Lin,Ham, Jong Hyun,Hage, Rosemary,Zhao, Wanying,Soto-Herná,ndez, Jaricelis,Lee, Sang Yeol,Paek, Seung-Mann,Kim, Min Gab,Boone, Charles,Coplin, David L.,Mackey, David Public Library of Science 2016 PLoS pathogens Vol.12 No.5

<▼1><P>Bacterial AvrE-family Type-III effector proteins (T3Es) contribute significantly to the virulence of plant-pathogenic species of <I>Pseudomonas</I>, <I>Pantoea</I>, <I>Ralstonia</I>, <I>Erwinia</I>, <I>Dickeya</I> and <I>Pectobacterium</I>, with hosts ranging from monocots to dicots. However, the mode of action of AvrE-family T3Es remains enigmatic, due in large part to their toxicity when expressed in plant or yeast cells. To search for targets of WtsE, an AvrE-family T3E from the maize pathogen <I>Pantoea stewartii</I> subsp. <I>stewartii</I>, we employed a yeast-two-hybrid screen with non-lethal fragments of WtsE and a synthetic genetic array with full-length WtsE. Together these screens indicate that WtsE targets maize protein phosphatase 2A (PP2A) heterotrimeric enzyme complexes via direct interaction with B’ regulatory subunits. AvrE1, another AvrE-family T3E from <I>Pseudomonas syringae</I> pv. tomato strain DC3000 (<I>Pto</I> DC3000), associates with specific PP2A B’ subunit proteins from its susceptible host Arabidopsis that are homologous to the maize B’ subunits shown to interact with WtsE. Additionally, AvrE1 was observed to associate with the WtsE-interacting maize proteins, indicating that PP2A B’ subunits are likely conserved targets of AvrE-family T3Es. Notably, the ability of AvrE1 to promote bacterial growth and/or suppress callose deposition was compromised in Arabidopsis plants with mutations of PP2A genes. Also, chemical inhibition of PP2A activity blocked the virulence activity of both WtsE and AvrE1 <I>in planta</I>. The function of HopM1, a <I>Pto</I> DC3000 T3E that is functionally redundant to AvrE1, was also impaired in specific PP2A mutant lines, although no direct interaction with B’ subunits was observed. These results indicate that sub-component specific PP2A complexes are targeted by bacterial T3Es, including direct targeting by members of the widely conserved AvrE-family.</P></▼1><▼2><P><B>Author Summary</B></P><P>Gram-negative bacterial pathogens employ type-III effector (T3E) proteins to suppress host immunity and promote disease symptoms. AvrE-family T3Es, which are widely distributed among plant-pathogenic bacteria, suppress host defense responses and also contribute to water-soaking, which is perhaps the most common symptom of bacterial diseases and likely results in the release of nutrients from host cells to promote pathogen growth. Despite the central virulence functions of AvrE-family T3Es, their mode of action remains enigmatic largely due to their cell toxicity. We report here that two AvrE-family T3Es, WtsE from the maize pathogen <I>Pantoea stewartii</I> subsp. <I>stewartii</I> and AvrE1 from the tomato and Arabidopsis pathogen <I>Pseudomonas syringae</I> pv. tomato, each target protein phosphatase 2A (PP2A) complexes in susceptible hosts via direct interaction/association with specific B’ regulatory subunits. Chemical inhibitors were used to demonstrate that PP2A activity is required for the virulence functions of WtsE and AvrE1. PP2A isoform specificity was also tested using mutants of Arabidopsis. More generally, PP2A subunits regulate, both positively and negatively, rapid pattern-triggered immune responses in Arabidopsis. Thus, bacterial T3Es target sub-component specific PP2A complexes to manipulate host immunity and cause disease symptoms during infection.</P></▼2>