Global environmental and toxicological impacts of polybrominated diphenyl ethers versus organophosphate esters: A comparative analysis and regrettable substitution dilemma.

The prevalence of organophosphate esters (OPEs) in the global environment is increasing, which aligns with the decline in the usage of polybrominated diphenyl ethers (PBDEs). PBDEs, a category of flame retardants, were banned and classified as persistent organic pollutants (POPs) through the Stockholm Convention due to their toxic and persistent properties. Despite a lack of comprehensive understanding of their ecological and health consequences, OPEs were adopted as replacements for PBDEs. This research aims to offer a comparative assessment of PBDEs and OPEs in various domains, specifically focusing on their persistence, bioaccumulation, and toxicity (PBT) properties. This study explored physicochemical properties (such as molecular weight, octanol-water partition coefficient, octanol-air partition coefficient, Henry's law constant, and vapor pressures), environmental behaviors, global concentrations in environmental matrices (air, water, and soil), toxicities, bioaccumulation, and trophic transfer mechanisms of both groups of compounds. Based on the comparison and analysis of environmental and toxicological data, we evaluate whether OPEs represent another instance of regrettable substitution and global contamination as much as PBDEs. Our findings indicate that the physical and chemical characteristics, environmental behaviors, and global concentrations of PBDEs and OPEs, are similar and overlap in many instances. Notably, OPE concentrations have even surged by orders of several magnitude compared to PBDEs in certain pristine regions like the Arctic and Antarctic, implying long-range transport. In many instances, air and water concentrations of OPEs have been increased than PBDEs. While the bioaccumulation factors (BAFs) of PBDEs (ranging from 4.8 to 7.5) are slightly elevated compared to OPEs (-0.5 to 5.36) in aquatic environments, both groups of compounds exhibit BAF values beyond the threshold of 5000 L/kg (log10 BAF > 3.7). Similarly, the trophic magnification factors (TMFs) for PBDEs (ranging from 0.39 to 4.44) slightly surpass those for OPEs (ranging from 1.06 to 3.5) in all cases. Metabolic biotransformation rates (LogKM) and hydrophobicity are potentially major factors deciding their trophic magnification potential. However, many compounds of PBDEs and OPEs show TMF values higher than 1, indicating biomagnification potential. Collectively, all data suggest that PBDEs and OPEs have the potential to bioaccumulate and transfer through the food chain. OPEs and PBDEs present a myriad of toxicity endpoints, with notable overlaps encompassing reproductive issues, oxidative stress, developmental defects, liver dysfunction, DNA damage, neurological toxicity, reproductive anomalies, carcinogenic effects, and behavior changes. Based on our investigation and comparative analysis, we conclude that substituting PBDEs with OPEs is regrettable based on PBT properties, underscoring the urgency for policy reforms and effective management strategies. Addressing this predicament before an exacerbation of global contamination is imperative.

Survey of medical students to assess their knowledge and attitudes toward organ transplantation and donation.

Kidney transplantation is the most preferred treatment modality for patients with end-stage renal disease (ESRD). This study aims at understanding the awareness, attitudes, and beliefs among the medical and nonmedical students. The study population consisted of 500 medical students and 39 nonmedical controls, who were surveyed using a reliable questionnaire that examined their knowledge and attitudes. A 24-item self-administered questionnaire, which assessed the levels of knowledge, attitude regarding organ donation with dichotomous scale and demographic data were used. Of the 500 medical students who received the questionnaire, 376 (75.2%) with a mean age of 22.1 ± 2.5 years responded; 39% were male, 43.6% were Bahraini, and 32.2% were from Saudi Arabia, 51.3% were in Grades-5 and 6 and 58.8% resided in big cities. The medical students had a highly positive attitude and great willingness toward organ donation. Majority of them (75.3%) knew the treatment of ESRD, and 70.7% recognized correctly that kidney transplantation is the optimal treatment for ESRD. However, only 10.4% knew that it is performed in Bahrain since 1995. A total of 241 participants (64.3%) reported positive attitude toward living kidney donation and 71.8% expressed their agreement to donation after death. More than half (66.8%) believed that their religion permits organ donation, although 56.6% of the participants believed that there is a danger after donating a kidney. When compared to nonmedical students, there was no statistically significant difference in the attitudes toward living kidney donation (P = 0.823) or organ donation after death (P = 0.066).

Cobalt-based nanoparticles prepared from MOF-carbon templates as efficient hydrogenation catalysts.

The development of efficient and selective nanostructured catalysts for industrially relevant hydrogenation reactions continues to be an actual goal of chemical research. In particular, the hydrogenation of nitriles and nitroarenes is of importance for the production of primary amines, which constitute essential feedstocks and key intermediates for advanced chemicals, life science molecules and materials. Herein, we report the preparation of graphene shell encapsulated Co3O4- and Co-nanoparticles supported on carbon by the template synthesis of cobalt-terephthalic acid MOF on carbon and subsequent pyrolysis. The resulting nanoparticles create stable and reusable catalysts for selective hydrogenation of functionalized and structurally diverse aromatic, heterocyclic and aliphatic nitriles, and as well as nitro compounds to primary amines (>65 examples). The synthetic and practical utility of this novel non-noble metal-based hydrogenation protocol is demonstrated by upscaling several reactions to multigram-scale and recycling of the catalyst.

MOF-derived cobalt nanoparticles catalyze a general synthesis of amines.

The development of base metal catalysts for the synthesis of pharmaceutically relevant compounds remains an important goal of chemical research. Here, we report that cobalt nanoparticles encapsulated by a graphitic shell are broadly effective reductive amination catalysts. Their convenient and practical preparation entailed template assembly of cobalt-diamine-dicarboxylic acid metal organic frameworks on carbon and subsequent pyrolysis under inert atmosphere. The resulting stable and reusable catalysts were active for synthesis of primary, secondary, tertiary, and N-methylamines (more than 140 examples). The reaction couples easily accessible carbonyl compounds (aldehydes and ketones) with ammonia, amines, or nitro compounds, and molecular hydrogen under industrially viable and scalable conditions, offering cost-effective access to numerous amines, amino acid derivatives, and more complex drug targets.

Molecular Retrofitting Adapts a Metal-Organic Framework to Extreme Pressure.

Despite numerous studies on chemical and thermal stability of metal-organic frameworks (MOFs), mechanical stability remains largely undeveloped. To date, no strategy exists to control the mechanical deformation of MOFs under ultrahigh pressure. Here, we show that the mechanically unstable MOF-520 can be retrofitted by precise placement of a rigid 4,4'-biphenyldicarboxylate (BPDC) linker as a "girder" to afford a mechanically robust framework: MOF-520-BPDC. This retrofitting alters how the structure deforms under ultrahigh pressure and thus leads to a drastic enhancement of its mechanical robustness. While in the parent MOF-520 the pressure transmitting medium molecules diffuse into the pore and expand the structure from the inside upon compression, the girder in the new retrofitted MOF-520-BPDC prevents the framework from expansion by linking two adjacent secondary building units together. As a result, the modified MOF is stable under hydrostatic compression in a diamond-anvil cell up to 5.5 gigapascal. The increased mechanical stability of MOF-520-BPDC prohibits the typical amorphization observed for MOFs in this pressure range. Direct correlation between the orientation of these girders within the framework and its linear strain was estimated, providing new insights for the design of MOFs with optimized mechanical properties.

Calcium l-Lactate Frameworks as Naturally Degradable Carriers for Pesticides.

Two porous, chiral metal-organic frameworks (MOFs), Ca14(l-lactate)20(acetate)8(C2H5OH)(H2O) (MOF-1201) and Ca6(l-lactate)3(acetate)9(H2O) (MOF-1203), are constructed from Ca2+ ions and l-lactate [CH3CH(OH)COO-], where Ca2+ ions are bridged by the carboxylate and hydroxyl groups of lactate and the carboxylate group of acetate to give a three-dimensional arrangement of Ca(-COO, -OH) polyhedra supporting one-dimensional pores with apertures and internal diameters of 7.8 and 9.6 Å (MOF-1201) and 4.6 and 5.6 Å (MOF-1203), respectively. These MOFs represent the first examples of extended porous structures based on Ca2+ and lactate. They show permanent porosity of 430 and 160 m2 g-1, respectively, and can encapsulate an agriculturally important fumigant, cis-1,3-dichloropropene. MOF-1201 shows a 100 times lower release rate compared with liquid cis-1,3-dichloropropene under the same test conditions (25 °C, air flow rate of 1 cm3 min-1). The hydrolysis of MOF-1201 in water makes it the first example of a degradable porous solid carrier for such fumigants.

Plasmon-Enhanced Photocatalytic CO(2) Conversion within Metal-Organic Frameworks under Visible Light.

Materials development for artificial photosynthesis, in particular, CO2 reduction, has been under extensive efforts, ranging from inorganic semiconductors to molecular complexes. In this report, we demonstrate a metal-organic framework (MOF)-coated nanoparticle photocatalyst with enhanced CO2 reduction activity and stability, which stems from having two different functional units for activity enhancement and catalytic stability combined together as a single construct. Covalently attaching a CO2-to-CO conversion photocatalyst ReI(CO)3(BPYDC)Cl, BPYDC = 2,2'-bipyridine-5,5'-dicarboxylate, to a zirconium MOF, UiO-67 (Ren-MOF), prevents dimerization leading to deactivation. By systematically controlling its density in the framework (n = 0, 1, 2, 3, 5, 11, 16, and 24 complexes per unit cell), the highest photocatalytic activity was found for Re3-MOF. Structural analysis of Ren-MOFs suggests that a fine balance of proximity between photoactive centers is needed for cooperatively enhanced photocatalytic activity, where an optimum number of Re complexes per unit cell should reach the highest activity. Based on the structure-activity correlation of Ren-MOFs, Re3-MOF was coated onto Ag nanocubes (Ag⊂Re3-MOF), which spatially confined photoactive Re centers to the intensified near-surface electric fields at the surface of Ag nanocubes, resulting in a 7-fold enhancement of CO2-to-CO conversion under visible light with long-term stability maintained up to 48 h.

Weaving of organic threads into a crystalline covalent organic framework.

A three-dimensional covalent organic framework (COF-505) constructed from helical organic threads, designed to be mutually weaving at regular intervals, has been synthesized by imine condensation reactions of aldehyde functionalized copper(I)-bisphenanthroline tetrafluoroborate, Cu(PDB)2(BF4), and benzidine (BZ). The copper centers are topologically independent of the weaving within the COF structure and serve as templates for bringing the threads into a woven pattern rather than the more commonly observed parallel arrangement. The copper(I) ions can be reversibly removed and added without loss of the COF structure, for which a tenfold increase in elasticity accompanies its demetalation. The threads in COF-505 have many degrees of freedom for enormous deviations to take place between them, throughout the material, without undoing the weaving of the overall structure.

Production of silver nanoparticles with strong and stable antimicrobial activity against highly pathogenic and multidrug resistant bacteria.

AIMS: To synthesize, characterize, and analyze antimicrobial activity of AgNPs of Escherichia hermannii (SHE), Citrobacter sedlakii (S11P), and Pseudomonas putida (S5). METHODS: The synthesized AgNPs were examined using ultraviolet-visible spectroscopy (UV-vis) and, zeta potential, and the size and the morphology obtained from the three different isolates were also confirmed by TEM. RESULTS: Among the three isolates tested, SHE showed the best antimicrobial activity due to the presence of small (4-12 nm) and stable (-22 mV) AgNPs. Stability of AgNPs was also investigated and found to be dependent on the nature of isolates. CONCLUSION: Produced AgNPs showed particle stability and antimicrobial efficacy up to 90 days of production. Our AgNPs exhibited greater antimicrobial activity compared with gentamicin against P. aeruginosa isolates and vancomycin against S. aureus and MRSA isolates at very low concentration (0.0002 mg per Microliters).