Biocompatibility of transition metal-substituted cobalt ferrite nanoparticles

Transition metals of copper, zinc, manganese, and nickel were substituted into cobalt ferrite nanoparticles via a sol-gel route using citric acid as a chelating agent. The microstructure and elemental compositions of the nanoparticles were characterized using scanning electron microscopy combined with energy dispersive X-ray spectroscopy. The particle size of the nanoparticles was investigated using particle size analyzer, and the zeta potentials were measured using zeta potential analyzer. The phase components of the synthesized transition metal-substituted cobalt ferrite nanoparticles were studied using Raman spectroscopy. The biocompatibility of the nanoparticles was assessed using osteoblast-like cells. Results indicated that the substitution of transition metals strongly influences the physical, chemical properties, and biocompatibility of the cobalt ferrite nanoparticles. © 2014 Springer Science+Business Media.

Electrochemical and spectroscopic investigation of redox processes for labile metal dithiocarbamate complexes

Although metal dithiocarbamate complexes have been studied extensively, there is in sate cases a distinct lack of data concerning redox properties and the products thereof. This is particularly true for complexes of the late transition and main group metals which are important in agriculture, industry, and chemical analysis. Hence, using electrochemical techniques, the redox behaviour of dithiocarbamate complexes of zinc, cadmium, mercury, lead, and tellurium has been examined. The products of oxidation and reduction have also been characterized by spectroscopic techniques (NMR, EPR, UV, and IR), mass spectrometry, conductivity, and Where possible, crystallographic study of an isolated compound. The species studied were without exception labile with the result that electrochemistry at mercury electrodes was influenced by the great stability of the mercury dithiocarbamate (Hg(RR’dtc) 2) complexes. Investigation of the latter showed that oxidative processes in the presence of mercury led to a new class of expounds: polymeric mercury dithiocarbamato cations. Oily one of these could be isolated as a solid, with the formula [Hg5(RR’dtc) 8](C104)2 For R=R’=ethyl the crystal structure was determined. For other metal dithiocarbamates the electrochemical behaviour at mercury electrodes in many ways paralleled that of the mercury analogues. Thus oxidative processes involved oxidation of electrode mercury to form mixed metal cationic species. Polarographic reduction led to the metal amalgam, usually via formation of mercury dithiocarbamate. Electrochemical studies at inert electrode materials such as platinum yielded distinctly different responses, with both oxidation and reduction being more difficult. Oxidation products at platinum electrodes gave identical polarographic responses to those firm mercury electrodes due to rapid interaction of the former with electrode mercury. The results are in sharp contrast to much of the previous work on transition metal dithiocarbamates for which electrochemical redox processes are often metal based arid not explicated by interaction with the electrode material.

Plasma-assisted self-catalytic vapour-liquid-solid growth of β-SiC nanowires

Long and straight β-SiC nanowires are synthesized via the direct current arc discharge method with a mixture of silicon, graphite and silicon dioxide as the precursor. Detailed investigations with x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectroscopy, Raman scattering spectroscopy, transmission electron microscopy and selected area electron diffraction confirm that the β-SiC nanowires, which are about 100–200 nm in stem diameter and 10–20 µm in length, consist of a solid single-crystalline core along the (1 1 1) direction wrapped with an amorphous SiO_x layer. A broad photoluminescence emission peak with a maximum at about 336 nm is observed at room temperature. A direct current arc plasma-assisted self-catalytic vapour–liquid–solid process is proposed as the growth mechanism of the β-SiC nanowires. This synthesis technique is capable of producing SiC nanowires free of metal contamination with a preferential growth direction and a high aspect ratio, without the designed addition of transition metals as catalysts.

Pro-oxidative synergic bactericidal effect of NO: kinetics and inhibition by nitroxides

NO plays diverse roles in physiological and pathological processes, occasionally resulting in opposing effects, particularly in cells subjected to oxidative stress. NO mostly protects eukaryotes against oxidative injury, but was demonstrated to kill prokaryotes synergistically with H2O2. This could be a promising therapeutic avenue. However, recent conflicting findings were reported describing dramatic protective activity of NO. The previous studies of NO effects on prokaryotes applied a transient oxidative stress while arbitrarily checking the residual bacterial viability after 30 or 60min and ignoring the process kinetics. If NO-induced synergy and the oxidative stress are time-dependent, the elucidation of the cell killing kinetics is essential, particularly for survival curves exhibiting a "shoulder" sometimes reflecting sublethal damage as in the linear-quadratic survival models. We studied the kinetics of NO synergic effects on H2O2-induced killing of microbial pathogens. A synergic pro-oxidative activity toward gram-negative and gram-positive cells is demonstrated even at sub-μM/min flux of NO. For certain strains, the synergic effect progressively increased with the duration of cell exposure, and the linear-quadratic survival model best fit the observed survival data. In contrast to the failure of SOD to affect the bactericidal process, nitroxide SOD mimics abrogated the pro-oxidative synergy of NO/H2O2. These cell-permeative antioxidants, which hardly react with diamagnetic species and react neither with NO nor with H2O2, can detoxify redox-active transition metals and catalytically remove intracellular superoxide and nitrogen-derived reactive species such as (•)NO2 or peroxynitrite. The possible mechanism underlying the bactericidal NO synergy under oxidative stress and the potential therapeutic gain are discussed.