Dorina Creanga

Chemically modified nanoparticles surface for sensing bacterial loading--experimental study based on fluorescence stimulation by iron ions.

The influence of iron ions supplied from magnetite nanoparticles with chemically modified surface on Pseudomonas aeruginosa germ was aimed--with experimental and theoretical approach of the intensity of the fluorescent signal emitted by the pyoverdine like siderophores. As the coated magnetic nanoparticles could function as probes, the possibility of designing a chemical device was considered based on the sensing of iron reduction from Fe(3+) into the more soluble Fe(2+), for detecting various levels of contamination (10 ÷ 10(8) cell/ml) of biological specimens and environmental samples. The proposed mathematical model estimated the fluorescence intensity due to siderophore synthesized by Pseudomonas, considering that the parameter describing the ion-bacteria interaction depends differently on the cell density for different magnetite nanoparticle coatings: linear dependence was found in the case of sodium oleate coating while power function was revealed for tetramethyl ammonium coating of magnetite nanocores, in both cases magnetite suspension being supplied in the same concentration (0.1 μl/ml). The calculated values of fluorescence intensity fitted the experimental data corresponding to magnetite supplied bacteria with graph slopes close to the unit and correlation coefficients of 0.999 and 0.996, while for the control samples, where that parameter was zeroed, correlation coefficient was found of 0.999.

Wet milling versus co-precipitation in magnetite ferrofluid preparation

Various uses of ferrofluids for technical applications continuously raise interest in the improvement and optimization of the preparation methods. This paper deals with the preparation of finely granulated magnetite particles coated with oleic acid in hydrocarbon suspensions following either chemical co-precipitation from iron salt precursors or wet milling of micron size mag- netite powder with the goal to compare the benefits and disadvantages of each method. Microstructural measurements showed that both methods gave similar- sized magnetite particles of 10-15 nm. The wet-milled magnetite suspension had a higher saturation magnetization than that obtained in the relatively rapid co-precipitation synthesis. The different efficacies of ferrophase incorporation into kerosene could be related to the different mechanisms of oleic acid bond- ing to the surface of the nanoparticles. Comparative data showed that wet milling represents a viable alternative to the traditional co-precipitation method since despite of longer processing time, the impact of chemicals on the envi- ronment and remnant water in the final product could be avoided.

Molecular modelling and spectral investigation of some triphenyltetrazolium chloride derivatives

The molecular parameters of 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) and some compounds based on triphenylformazans (TPFs) — resulting from the enzymatic transformation of TTC, were subjected to comparative investigation on the basis of semi-empirical quantum-chemical simulations, revealing some changes in dipole moment and polarisability in the TPFs in comparison with TTC. Chemical shift due to substituents was discussed using electronic absorption bands in the UV-VIS range recorded for diluted solutions in various solvents as well as the absorption spectra recorded in the infrared range for KBr dispersions. The correlation of the spectral shift of the electronic absorption bands with a specific function on the solvent refractive index, as recommended by theoretical studies focused on solute-solvent interactions, revealed the major role played by dispersive and induction forces. For several solvents, a different behaviour could be assigned to specific interactions overlapping with universal solute-solvent interactions.

Nanotechnological Application Based on CoFe2O4 Nanoparticles and Electromagnetic Exposure on Agrotechnical Plant Growth

This study is focused on the bioeffects of nanoparticulate metallic matter and electromagnetic exposure on agrotechnical plant cultures, designed in the general context of soil, water and air pollution. Nanotechnological procedure was carried out to yield magnetic nanoparticles (MNPs) similar to those used for various biomedical purposes for human life improvement but finally leading to MNPs delivery in the waste waters and consequently loading soil with metal ions. CoFe2O4 MNPs were synthesized by chemical route and suspended in deionized water. Microstructural and magnetic properties were evidenced by investigations through standard solid state methods. Equal volumes of 80 μl/l MNP suspension equivalent to 1016 MNPs/ml were supplied to Helianthus annuus seedlings for 12 days. Identical sample array was exposed also to low power density microwaves for 1-2-4 hours daily. Plant response was observed using measurements of assimilatory pigment contents in green tissues of seedlings.

Genotoxicity of Nanoparticulate Zinc Ferrite – Possible Application in Plant Biotechnology

Nanoparticulate matter, mainly nanoparticles containing metal ions could represent a promising biotechnological tool when preliminary testing could indicate the ability of inducing chromosomal changes in the plant tissues. Chemical route was applied as synthesis method of ZnFe2O4 powder with nanometric size, thus enabling plants to internalize the particles through endocytosis for further lysosomal digestion. Surface modification with long chain molecular shell was chosen to ensure nanoparticle stability in water dispersion. We present the results of some genetic effects induced by such prepared zinc ferrite nanoparticles as diluted suspension when supplied to agrotechnical plant species of large interest namely sunflower. Various and numerous chromosomal aberrations were identified that could be perpetuated in the form of genetic mutations through adequate biotechnology. Quantitative analysis emphasized remarkable influence of ZnFe2O4 nanoparticles on meristem tissues of freshly germinated seeds which suggested possible new biotechnological tool based on nanotoxicity application in genetics research.

Iron oxide-silica nanocomposites yielded by chemical route and sol–gel method

Magnetic nanoparticles yielded by chemical route were surface modified with stabilizing agents being further coated by sol–gel method with silica shell to be used for various applications. Iron oxide magnetic cores were dispersed in water by single citrate layer and, respectively, by double oleate hydrophilic coating. Sol–gel reaction with tetraethylorthosilicate provided further coating with silica that confers increased reactivity for ligand coupling. Microstructural and magnetic properties were investigated by standard methods evidencing nanometric size, good crystallinity, and superparamagnetic behavior. Comparative analysis evidenced similar crystallite size for both citrate- and oleate-coated magnetic nanoparticles, while granularity was changed after silica adding. Saturation magnetization diminished less for oleate-stabilized nanoparticles than for citrate-stabilized ones after silica coating and moderate thermal treatment. Such prepared magnetic nanocomposites could have possible utilization as magnetic vectors for targeted biomolecules.Graphical Abstract

Oleate Coated Magnetic Cores Based on Magnetite, Zn Ferrite and Co Ferrite Nanoparticles—Preparation, Physical Characterization and Biological Impact on Helianthus Annuus Photosynthesis

Sodium oleate was used as coating shell for magnetite, Zn ferrite and Co ferrite powders to stabilize them in the form of aqueous magnetic suspensions. The physical characterization was carried out by applying X‐ray diffraction and magnetization measurements. Both crystallite size and magnetic core diameter ranged between 7 and 11 nm. The influence of magnetic nanoparticle suspensions (corresponding to magnetic nanoparticle levels of 10−14–10−15/cm3) on sunflower seedlings was studied considering the changes in the photosynthesis pigment levels. Similar responses were obtained for magnetite and cobalt ferrite nanoparticle treatment consisting in the apparent inhibition of chlorophyll biosynthesis while for zinc ferrite nanoparticles some concentrations seemed to have stimulatory effects on the chlorophylls as well as on the carotene levels. But the chlorophyll ratio was diminished in the case of all three types of magnetic nanoparticles meaning their slight negative effect on the light harvesting complex ...

Computational and solvatochromic study of pyridinium-acetyl-benzoyl-methylid (PABM)

Pyridinium-acetyl-benzoyl-methylid is a cycloimmonium ylid studied here from structural and spectral point of view. Quantum mechanical analysis offers information about the most stable spatial structure, the electro-optical properties in the ground electronic state as well as the QSAR parameters of PABM. The solvatochromic study of the visible absorption band of PABM was made in order to establish the electro-optical features of the ylid in the excited electronic state and also to approximate the contribution of different types of intermolecular interactions in solutions with different solvents. The ternary solutions of PABM were used to estimate the difference between the interaction energies in molecular pairs of the types: ylid-inactive solvent and ylid-active solvent from interaction point of view.

Small-angle neutron scattering investigations of Co-doped iron oxide nanoparticles. Preliminary results

Preliminary small-angle neutron scattering investigations on aqueous suspensions of several cobalt doped ferrites (CoxFe3-xO4, x=0; 0.5; 1) nanoparticles prepared by chemical co-precipitation method, are reported. The measurements were accomplished at the YuMO instrument in function at the IBR-2 reactor. Results of intermediary data treatment are presented and discussed.

Antioxidant properties evidenced by polyphenols content in two Romanian red grape cultivars in Iasi area

Environment protection and management includes preservation of agroindustrial plant species with certificated biological features as source of healthy and safe foods and drinks. Antioxidant properties of fruits were evidenced by total polyphenols content of different parts of grapes (skins, pulps and seeds) in two grape cultivars (Cabernet Sauvignon and Merlot) from two experimental fields (Copou and Bucium vineyards). The total phenolic contents of seeds ranged from 116.56 to 127.90 mg GAE/g lyophilized matter in Merlot cultivars and from 101.64 to 109.29 mg GAE/g lyophilized matter in Cabernet cultivars. Our research reveal that there are variations in total polyphenols content within investigated grape cultivars, both in terms of analyzed fruit components as well as by the location of the two collecting points.