DFT study on the regio- and stereoselectivity of the organocatalytic aza-Diels-Alder reaction of crotonaldehyde and cyclic 1-aza-1,3-butadiene

The mechanism of 1,4-, 1,2-, and 3,4-cyclization reactions of cyclic 1-azadiene 1 with an organocatalyst 4 has been studied theoretically using DFT method. The reactions proceed in a stepwise fashion, with zwitterionic intermediates. The most favorable cyclization reaction takes place along the C–C pathway of the 1,4-cyclization reaction, under a combination of kinetic and thermodynamic control. The reaction is characterized by the nucleophilic attack of 4 (C₅) to the electrophilic center of 1 (C₁), leading to the formation of cycloadduct 6, which correctly explains the source of the regioselectivity.

     

Improving piezoelectric and pyroelectric properties of electrospun PVDF nanofibers using nanofillers for energy harvesting application

In this study, it was aimed to increase the piezoelectric and pyroelectric properties of electrospun polyvinylidene fluoride (PVDF) nanofibers simultaneously by using specific nanofillers. Graphene oxide (GO), graphene, and halloysite nanotubes with different concentrations (0, 0.05, 0.4, and 1.6% wt/wt) were combined with PVDF solution and were fabricated in the form of nanofibers through electrospinning. Pyroelectric properties of samples were measured by submerging sealed samples in hot water (360°K) and ice (270°K). The piezoelectric properties of the samples were evaluated through bending tests. The microstructural, mechanical, and thermal properties of the electrospun PVDF nanocomposite were investigated using scanning electron microscope, Instron instrument, and thermogravimetric analysis, respectively. To further support the experimental observations for generating electric voltage in the bended nanogenerator, the PVDF nanogenerator (PNG) was also modeled by a finite element analysis based on the theory of linear piezoelectricity using COMSOL Multiphysics simulation software. Experimental results showed that adding nanofillers could improve the piezoelectric and pyroelectric properties of all samples, associated with the increment of β‐phase in the nanofibers. It was concluded that adding nanofillers could increase pyroelectricity about 50% more than piezoelectricity in pristine PVDF nanofiber web. The PNG containing 1.6 wt% GO showed the highest efficiency in terms of piezoelectricity and pyroelectricity. In addition, the results showed that the ratio of piezoelectric to pyroelectric coefficients was constant (~1.5) and it was independent of the nanofiller type and content. The effect of external force and vibration frequency on the output voltage was also investigated. Increasing the compressive force and vibration frequency caused a greater output voltage. Finally, the fabricated nanogenerator was integrated on insole and elbow to investigate its energy harvesting capabilities from body movement.     

Collagen of porcine auricle has unique biochemical and biophysical characteristics

Collagen is a major component of the extracellular matrix and is used as a material in tissue engineering. We demonstrated the extraction of atelocollagen from porcine auricular and characterized its unique physical and biochemical properties. Extracted type I collagens of auricular collagen using acetic acid and pepsin (PAC) showed superior fibrillogenesis and viscoelasticity compared to type I collagen from porcine skin. The observation of PAC fibrils by transmission electron microscopy and Atomic Force Microscope under physiological conditions revealed long fibrils with pronounced 3D structures, while type I collagen from porcine skin revealed a flat structure. Furthermore, a PAC-coated plate promoted higher cell proliferation than when grown on a skin type I collagen-coated plate. Porcine auricular type I collagen has superior biophysical and biological properties in terms of viscoelasticity, fibrillogenesis, and cell proliferation, and can be used in further studies toward novel potential applications in the field of medical materials.     

Highly Efficient One‐Pot Three‐Component Synthesis and Antimicrobial Activity of 2‐Amino‐4H‐chromene Derivatives

A remarkably efficient three‐component reaction to synthesize 2‐amino‐4H‐chromenes derivatives from malononitrile, various aromatic aldehydes, and orcinol was described at room temperature in CH₂Cl₂ in the presence of catalytic amount of triethylamine. In a facile one‐pot procedure, excellent yields of products were achieved in less than 1 h. Some of the synthesized 2‐amino‐4H‐chromenes derivatives demonstrated potent antibacterial activities against Gram‐positive bacteria including Staphylococcus aureus and Bacillus anthracis, indicated by disk method, minimum inhibitory concentration, and minimum bactericidal concentration approaches. However, none of the tested compounds expressed any antibacterial activities against Enterococcus faecalis and Gram‐negative bacteria.     

A Synergistic Effect of Phthalimide-Substituted Sulfanyl Porphyrazines and Carbon Nanotubes to Improve the Electrocatalytic Detection of Hydrogen Peroxide

A sulfanyl porphyrazine derivative with peripheral phthalimide moieties was metallated with cobalt(II) and iron(II) metal ions. The purity of the macrocycles was confirmed by HPLC, and subsequently, compounds were characterized using various analytical methods (ES-TOF, MALDI-TOF, UV–VIS, and NMR spectroscopy). To obtain hybrid electroactive electrode materials, novel porphyrazines were combined with multiwalled carbon nanotubes. The electrocatalytic effect derived from cobalt(II) and iron(II) cations was evaluated. As a result, a significant decrease in the overpotential was observed compared with that obtained with bare glassy carbon (GC) or glassy carbon electrode/carbon nanotubes (GC/MWCNTs), which allowed for sensitive determination of hydrogen peroxide in neutral conditions (pH 7.4). The prepared sensor enables a linear response to H₂O₂ concentrations of 1–90 µM. A low detection limit of 0.18 μM and a high sensitivity of 640 μA mM⁻¹ cm⁻² were obtained. These results indicate that the obtained sensors could potentially be applied in biomedical and environmental fields.     

Synthesis of Novel Phthalazino[1,2‐b]quinazolinedione Derivatives: Efficient and Practical Reaction of 2‐Amino‐N′‐Arylbenzohydrazides and 2‐Formylbenzoic Acids

This work reported the synthesis of novel phthalazino[1,2‐b]quinazolinedione derivatives through the reaction of 2‐amino‐N′‐arylbenzohydrazides and 2‐formylbenzoic acids in the presence of TsOH in EtOH under reflux conditions.     

Radiolabeling of zoledronic acid with <Superscript>188</Superscript>Re as a new palliative agent radiotracer in treatment of bone tumors

Zoledronic acid is a bisphosphonates to treat bone problems. Rhenium-188-zoledronic acid could be used as a palliate agent in skeletal metastases. Radiolabeled product was prepared through optimized radiochemical procedures. The organs uptake especially bone uptake assessed in healthy animals mice. The radiochemical purity of the radiotracer was > 95% which was stable up to 24 h. Bone uptake (1.08?±?0.14% ID/g at 1 h) with retention of activity in bone up to 24 h (0.26?±?0.06% ID/g) was reached. This radiotracer can be used as a developing candidate for a palliative treatment of bone metastasis.