ABSTRACT
In situ generated gold nanoparticles inside the nanospaces of periodic mesoporous organosilica with an imidazolium framework (Au@PMO-IL) were found to be highly active, selective, and reusable catalysts for the aerobic oxidation of activated and nonactivated alcohols under mild reaction conditions. The catalyst was characterized by nitrogen adsorption-desorption measurement, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), elemental analysis (EA), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The catalyst exhibited excellent catalytic activity in the presence of either Cs2CO3 (35 °C) or K2CO3 (60 °C) as reaction bases in toluene as a reaction solvent. Under both reaction conditions, various types of alcohols (up to 35 examples) including activated benzylic, primary and secondary aliphatic, heterocyclic, and challenging cyclic aliphatic alcohols converted to the expected carbonyl compounds in good to excellent yields and selectivity. The catalyst was also recovered and reused for at least seven reaction cycles. Data from three independent leaching tests indicated that amounts of leached gold particles were negligible (<0.2 ppm). It is believed that the combination of bridged imidazolium groups and confined nanospaces of PMO-IL might be a major reason explaining the remarkable stabilization and homogeneous distribution of in situ generated gold nanoparticles, thus resulting in the highly active and recyclable catalyst system.
Subject(s)
Alcohols/chemistry , Gold/chemistry , Ionic Liquids/chemistry , Metal Nanoparticles/chemistry , Catalysis , Organosilicon Compounds/chemistry , Oxidation-ReductionABSTRACT
In recent years, the problems associated with bacterial resistance to antibiotics caused nanodrugs to be considered as a new way for infectious diseases treatment. The main purpose of this study was to develop a new agent against Pseudomonas aeruginosa, a very difficult bacterium to treat, based on azlocillin antibiotic and silver nanoparticles (AgNPs). Azlocillin was conjugated with AgNPs by chemical methods and its antimicrobial activity was studied against P. aeruginosa using well diffusion agar method. Then, minimum inhibitory concentration and minimum bactericidal concentration of the new conjugate was specified with macro-dilution method. The animal study showed the considerable enhanced antibacterial effect of azlocillin in conjugation with AgNPs against P. aeruginosa in comparison with azlocillin alone, AgNPs alone and azlocillin in combination with AgNPs.
Subject(s)
Anti-Bacterial Agents/pharmacology , Azlocillin/pharmacology , Metal Nanoparticles/chemistry , Pseudomonas aeruginosa/drug effects , Silver/pharmacology , Animals , Female , Mice , Mice, Inbred BALB C , Microbial Sensitivity Tests , Silver/chemistry , Spectroscopy, Fourier Transform InfraredABSTRACT
Even though the therapeutic efficacy of numerous antimicrobial drugs has been well established, inefficient delivery can result in an inadequate therapeutic index. Gold nanoparticles have unique physicochemical properties such as large surface area to mass ratio and functionalizable structure. These properties can be applied to facilitate the administration of antimicrobial drugs, thereby overcoming some of the limitations in traditional antimicrobial therapeutics. In this study, gold nanospheres were used as a drug carrier system for gentamicin delivery to Staphylococcal infected foci. Conjugation of gentamicin with gold nanospheres was performed in HEPES buffer. The attachment of gentamicin to gold nanospheres was confirmed by UV/Vis spectroscopy. The HPLC and atomic absorption spectrometer analyses showed that 347 gentamicin molecules were attached to each gold nanosphere. Minimum inhibitory concentration and minimum bactericidal concentration studies showed the enhanced antibacterial effect of gentamicin-gold nanospheres complex in comparison with free gentamicin. The biodistribution study showed the localization of the complex at the site of Staphylococcal infection foci with high sensitivity in mouse model.
