Hydrazone analogues with promising antibacterial profiles: Synthesis, morphology, in vitro and in silico approaches.

The emergence of resistance to antibacterial drugs remains an important global threat that necessitates an urgent need for the discovery of alternative drugs. This study was undertaken to synthesize some novel nitroaryl/heteroaryl hydrazone derivatives as potential antibacterial agents. After synthesizing by a simple reaction between quinoline/quinazoline hydrazine and nitroaryl/heteroaryl aldehydes, all the compounds were screened for their antibacterial activities, cytotoxicity and in silico investigations. The compound, 2-(4-nitrobenzylidene)-1-(quinazolin-4-yl)hydrazine (1b), displayed significant antimicrobial activity against several susceptible and resistant bacteria without any cytotoxicity. Moreover, scanning electron microscopy (SEM) revealed the complete destruction of Staphylococcus aureus and Escherichia coli following exposure to this compound after 2 h exposure. The in silico studies confirmed the better binding energy of these compounds in comparison with the reference drugs in complex with topoisomerase IV and bacterial ribosomal receptor. Compound 1b can be considered a promising lead compound for the development of broad-spectrum antibacterial medications after further studies.

Fabrication of copper(II)-coated magnetic core-shell nanoparticles Fe3O4@SiO2-2-aminobenzohydrazide and investigation of its catalytic application in the synthesis of 1,2,3-triazole compounds.

In the present work, an attempt has been made to synthesize the 1,2,3-triazole derivatives resulting from the click reaction, in a mild and green environment using the new copper(II)-coated magnetic core-shell nanoparticles Fe3O4@SiO2 modified by isatoic anhydride. The structure of the catalyst has been determined by XRD, FE-SEM, TGA, VSM, EDS, and FT-IR analyzes. The high efficiency and the ability to be recovered and reused for at least up to 6 consecutive runs are some superior properties of the catalyst.

Biological and nano-indentation properties of polybenzoxazine-based composites reinforced with zirconia particles as a novel biomaterial.

INTRODUCTION: The biological and mechanical properties of substances are relevant to their application as biomaterials and there are many efforts to enhance biocompatibility and mechanical properties of bio-medical materials. OBJECTIVES: In this study, to achieve a low rate of shrinkage during polymerization, good mechanical properties, and excellent biocompatibility, benzoxazine based composites were synthesized. METHODS: Benzoxazine monomer was synthesized using a solventless method. FTIR and DSC analysis were carried out to determine the appropriate polymerization temperature. The low viscosity of the benzoxazine monomer at 70°C attract us to use in situ polymerization after high speed ball milling of the benzoxazine and it mixture with different weight fractions of zirconia particles. Dispersion and adhesion between the ceramic and polymer components were evaluate by SEM. To evaluate the biological properties and toxicity of the polybenzoxazine-based composite samples reinforced with zirconia particles, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay was conducted. The micromechanical properties of each composite were evaluated by more than 20 nanoindentation tests and 3 nanoscratching tests. Surface topography of scratched regions was investigated using Atomic Force Microscopy. Shrinkage was simulated by Materials Studio software. RESULTS: SEM images showed good dispersion and adhesion between the ceramic and polymer components. Biocompatibility assay showed excellent in vitro biocompatibility. Nano-indentation force-displacement curves showed matrix, reinforcement and interphase regions in specimens and excellent homogeneity in mechanical properties. The nanoindentation results showed that the addition of zirconia particles to the polybenzoxazine matrix increased the modulus and hardness of the neat polybenzoxazine; however, by adding more than an optimum level of reinforcement particles, the mechanical properties decreased due to the agglomeration of reinforcement particles and weak interphase that cause inappropriate load transferring between matrix and reinforcement particles. Results of nano-scratching tests showed effects of zirconia particles as reinforcement on the coeffiecient of friction of the synthesized composites. Shrinkage simulation showed a low rate of shrinkage for polybenzoxazine in comparison with other low shrinkage polymers, such as Bis-GMA. CONCLUSION: Polybenzoxazine based composites that reinforced with an optimum amount of zirconia particles (60% wt micro and 10% wt nano-particles) could be used as a novel biomaterial duo to its excellent biocompatibility, good mechanical properties, appropriate viscosity and low rate of polymeization shrinkage.

The exponent 3/2 at pyramidal nanoindentations.

The analysis of published loading curves reveals the exponent 3/2 to the depth for nanoindentations with sharp pyramidal or conical tips. This has geometric reasons, as it occurs independent on the bonding states and indentation mechanisms. Nevertheless, most mathematical deductions and finite element simulations of nanomechanical parameters in the literature continue using the experimentally not supported Hertzian exponent 2. Therefore, numerous published loading curves of various authors are plotted using the experimental exponent 3/2 to present unbiased proof for its generality with metals, oxides, semiconductors, biomaterials, polymers, and organics. Linearity is independent of equipment and valid for load controlled, or depth controlled, or continuous stiffness, or AFM force measurements. The linearity with exponent 3/2 often extends from the nano- into the microindentation ranges. The tip rounding and taper influence of the "geometrical similar" indenters are discussed. When kinks occur in such linear plots through the origin, these indicate change of the materials' mechanical properties under pressure by phase transition. These events are discussed for nanoindentations with respect to the known hydrostatic transformation pressures that are, of course, always higher than the necessary indentation mean pressure. Numerous Raman, as well as X-ray and electron diffraction results from the literature support the phase transitions that are now easily detected. Nanoporous materials first fill the pores upon indentation. Published loading curves exhibit more information than hitherto assumed.