Fabrication and characterization of biocompatible nacre-like structures from α-zirconium hydrogen phosphate hydrate and chitosan

Composite materials with an ordered layered structure resembling that of nacre were fabricated by layer-by-layer assembly making use of presynthesized α-zirconium hydrogenphosphate hydrate (ZrP) platelets and chitosan. These two biocompatible materials were chosen in view of possible applications in the biomedical field, e.g., as bone or joint replacement implants. The effect of different concentrations of the inorganic ZrP platelets and the organic components (chitosan) on the composite assembly and structure was investigated. A high concentration of chitosan (0.1 wt.%) resulted in a misalignment of the inorganic platelets, while at very low concentrations (0.001 wt.%), the substrate was not fully covered by the polymer, again leading to misalignment. Also, the concentration of the α-ZrP platelets affected the composite assembly and structure. The number of dipping cycles was varied between 70 and 220, yielding a maximum thickness of approximately 6 μm. The pH value of the chitosan solution was also varied to investigate its influence on the composite assembly. The mechanical properties of the composites were tested with a nanoindenter. For samples prepared with the same number of dipping cycles, higher values of Young's modulus and hardness were obtained with improved alignment of the platelets in the samples. For samples prepared with 220 dipping cycles, a Young's modulus of 2.6 GPa and a hardness of 70 MPa were observed. Important general relationships are recognized between the preparation parameters, the degree of order within the nacre-like films and the resulting mechanical properties.     

Synthesis of 1,2-dihydroquinolin-2-ylphosphonates and 1,2-dihydroisoquinolin-1-ylphosphonates via three-component reactions

Abstract  

A facile stereoselective synthesis of 1,2-dihydroquinolin-2-ylphosphonate and 1,2-dihydroisoquinolin-1-ylphosphonate derivatives by the three-component reactions of quinoline or isoquinoline, dialkyl acetylenedicarboxylates, and hydrogen phosphonates is described.     

Zinc chloride catalyzed three-component Ugi reaction: synthesis of N-cyclohexyl-2-(2-hydroxyphenylamino)acetamide derivatives

The ability of zinc chloride as a catalyst to promote the three-component Ugi reaction of 2-aminophenols, aliphatic or aromatic aldehydes, and cyclohexyl isocyanide in methanol at room temperature is described. The N-cyclohexyl-2-(2-hydroxyphenylamino) amide products are obtained in high yields. When N,N-dimethylformamide dimethyl acetal and triethyl orthoformate, as two new components of the three-component Ugi reaction are used instead of the aldehyde the reaction gives N-cyclohexyl-2-(dimethylamino)-2-(2-hydroxyphenylamino)acetamide and N-cyclohexyl-2-(2-hydroxyphenylamino)-2-ethoxyacetamide derivatives, respectively.     

Computational study of the conformational space of methyl 2,4-diacetyl-beta-D-xylopyranoside: 4C1 and 1C4 chairs, skew-boats (2SO, 1S3), and B3,O boat forms

Ring and substituent rotamer conformations of methyl 2,4-diacetyl-beta-D-xylopyranoside, for which experimental results are controversial, were studied in the gas phase and in solvents of different polarity (CCl4, CHCl3, DMSO, and H2O) by B3LYP density functional theory. The 1C4 chair is the most stable ring form in the gas phase, followed by 4C1 and 2S0. Solvents of increasing polarity shift the equilibrium toward the 4C1 chair. Homodesmotic reaction energies show that the 1C4 and 2SO forms are stabilized by hydrogen bonding and anomeric effects and that steric repulsion is smallest in the 4C1 chair and largest in skew-boats.     

Electrochemistry and Adsorptive Stripping Voltammetric Determination of Amoxicillin on a Multiwalled Carbon Nanotubes Modified Glassy Carbon Electrode

The study of electrochemical behavior of amoxicillin (AMX), a β‐lactam antibiotic, is described on a multiwalled carbon nanotubes (MWCNTs) modified electrode by electrochemical impedance spectroscopy (EIS) and adsorptive stripping voltammetry for sensitive determination of AMX in pharmaceutical and human urine samples within a wide pH range from 2.0 to 10.0. Also, studies by Fe₂O₃ nanoparticles modified carbon paste electrode show that iron oxide impurities in the MWCNTs are not active sites for sensing of amoxicillin. Under optimized conditions, the oxidation peak has two linear dynamic ranges of 0.6–8.0 and 10.0–80.0 μM with a detection limit of 0.2 μM and a precision of <4%.     

Loading of ZIF-67 on silk with sustained release of iodine as biocompatible antibacterial fibers

Antibacterial fibers have great potential in numerous applications, including bandages, surgical robes, and surgical sutures, and play a significant role in our everyday lives. Here, zeolitic imidazolate framework-67 was synthesized using a green method on silk fibers through a layer-by-layer process under ultrasonic irradiation (ZIF-67@silk [U]) and without ultrasonic irradiation (ZIF-67@silk [B]). Then, iodine was loaded on ZIF-67@silk samples and were assessed as antibacterial fibers with iodine release. Four samples of ZIF-67@silk and I₂@ZIF-67@silk were characterized by FT-IR, PXRD, FE-SEM, TGA, BET, and UV–Vis spectroscopy. Finally, antibacterial activity of ZIF-67@silk (B and U) and I₂@ZIF-67@silk (B and U) on Staphylococcus aureus as Gram-positive bacteria and Escherichia coli as Gram-negative bacteria was investigated. In addition to ZIF-67@silk samples, iodine-loaded samples showed excellent antimicrobial facility.     

Enhanced bactericidal and in vivo wound healing potential of biosynthesized zinc oxide nanoparticles from psyllium mucilage

The multifunctional zinc oxide nanoparticles are synthesized using a cost-effective, efficient, eco-friendly, simple, and clean synthesis approach. Herein, we reported the antibacterial and wound healing potential of zinc oxide nanoparticles (ZnO-NPs) prepared using psyllium gel (PG) as the reducing and stabilizing agent. The PG-mediated zinc oxide nanoparticles (PG-ZnO-NPs) were characterized using UV–Vis, photoluminescence (PL), FTIR, XRD, Raman, and SEM. UV–Vis spectral studies confirmed the surface plasmonic resonance (SPR) band at 364 nm. PL results demonstrated the fluorescent or emission nature of PG-ZnO-NPs. FTIR analysis confirmed characteristic peaks at 873.82 and 619.88 cm⁻¹ due to the tetrahedral coordination of zinc and the formation of the Zn-O bond. XRD and Raman confirm the formation of PG-ZnO-NPs, whereas SEM analysis revealed PG-ZnO-NPs are rod-shaped, having hexagonal prism-like bases, and EDX exhibited the elemental composition of PG-ZnO-NPs. The as-synthesized PG-ZnO-NPs possessed prominent microbicidal potential against gram-positive (Bacillus subtilis and Bacillus licheniformis) and gram-negative (Escherichia coli and Salmonella shigella) bacterial strains in terms of zone of inhibition (ZOI), minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC). In vivo biological investigations with mice show that the synthesized PG-ZnO-NPs possess outstanding biocompatibility and wound healing potential. PG-ZnO-NPs dressing significantly speeds up full-thickness wound repair by triggering a decrease in MMP-1 and MMP-2 and escalating the mRNA levels of collagen types (I & III) and fibronectin. Thus, our work validates that the inclusion of PG-ZnO-NPs in dressing shows excellent potential for acute wound management.