Electric Discharge Plasmochemical Synthesis of Carbon Nanomaterials

High-energy electric discharge technologies (electric breakdown and HF volume discharge in organic media) for a large scale synthesis of amorphous carbon (AC) are developed. A destruction of hydrocarbon molecules into separate fragments occurs during such processing of organic media, what results in AC formation in the process of ultra-fast cooling of the clusters. To investigate the influence of chemical nature of working media, organic liquids and gases from the class of arenes with sp2-hybridisation of carbon atoms in molecule and alkanes with sp3-hybridisation were used. Performed XRD, HRTEM and Raman studies showed that produced powders are typical amorphous materials with significant degree of disorder. But only in the case of electric breakdown of alkanes, carbon nanomaterials with complex core-shell structure were discovered. Individual particles of onion-like carbon (OLC) consist of ~ 5 nm core surrounded by graphitic shell of 5-6 layers. Synthesized OLC is used as antifriction additives to industrial oils and as material for electromagnetic waves shielding. The statistical analysis of the atomic structure of the synthesized materials using reverse Monte Carlo and Voronoi-Delaunay methods was performed. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3509

Effects of Antibiotic Physicochemical Properties on Their Release Kinetics from Biodegradable Polymer Microparticles

Purpose: This study investigated the effects of the physicochemical properties of antibiotics on the morphology, loading efficiency, size, release kinetics, and antibiotic efficacy of loaded poly(DL-lactic-co-glycolic acid) (PLGA) microparticles (MPs) at different loading percentages. Methods: Cefazolin, ciprofloxacin, clindamycin, colistin, doxycycline, and vancomycin were loaded at 10 and 20 wt% into PLGA MPs using a water-in-oil-in water double emulsion fabrication protocol. Microparticle morphology, size, loading efficiency, release kinetics, and antibiotic efficacy were assessed. Results: The results from this study demonstrate that the chemical nature of loaded antibiotics, especially charge and molecular weight, influence the incorporation into and release of antibiotics from PLGA MPs. Drugs with molecular weights less than 600 Da displayed biphasic release while those with molecular weights greater than 1,000 Da displayed triphasic release kinetics. Large molecular weight drugs also had a longer delay before release than smaller molecular weight drugs. The negatively charged antibiotic cefazolin had lower loading efficiency than positively charged antibiotics. Microparticle size appeared to be mainly controlled by fabrication parameters, and partition and solubility coefficients did not appear to have an obvious effect on loading efficiency or release. Released antibiotics maintained their efficacy against susceptible strains over the duration of release. Duration of release varied between 17 and 49 days based on the type of antibiotic loaded. Conclusions: The data from this study indicate that the chemical nature of antibiotics affects properties of antibiotic-loaded PLGA MPs and allows for general prediction of loading and release kinetics