Nosocomial diseases are mainly caused by two common pathogens, Escherichia coli and Staphylococcus aureus, which are becoming more and more resistant to conventional antibiotics. Therefore, it is becoming increasingly necessary to find other alternative treatments than commonly utilized drugs. A promising strategy is to use nanomaterials such as selenium nanoparticles. However, the ability to produce nanoparticles free of any contamination is very challenging, especially for nano-medical applications. This paper reports the successful synthesis of pure selenium nanoparticles by laser ablation in water and determines the minimal concentration required for ~50% inhibition of either E. coli or S. aureus after 24 hours to be at least ~50 ppm. Total inhibition of E. coli and S. aureus is expected to occur at 107±12 and 79±4 ppm, respectively. In this manner, this study reports for the first time an easy synthesis process for creating pure selenium to inhibit bacterial growth.

In this paper a new atomic force sensing technique is presented for dynamically probing conformational changes in proteins. The method is applied to the light-induced changes in the membrane-bound proton pump bacteriorhodopsin (bR). The microsecond time-resolution of the method, as presently implemented, covers many of the intermediates of the bR photocycle which is well characterized by spectroscopical methods. In addition to the native pigment, we have studied bR proteins substituted with chemically modified retinal chromophores. These synthetic chromophores were designed to restrict their ability to isomerize, while maintaining the basic characteristic of a large lightinduced charge redistribution in the vertically excited Franck--Condon state. An analysis of the atomic force sensing signals lead us to conclude that protein conformational changes in bR can be initiated as a result of a light-triggered redistribution of electronic charge in the retinal chromophore, even when isomerization cannot take place. Although the coupling mechanism of such changes to the light-induced proton pump is still not established, our data question the current working hypothesis which attributes all primary events in retinal proteins to an initial transNcis isomerization.

A magnetically controlled elastically driven electroporation phenomenon, or magneto-elasto-electroporation (MEEP), is discovered while studying the interactions between core-shell magnetoelectric nanoparticles (CSMEN) and biological cells in the presence of an a.c. magnetic field. In this paper we report the effect of MEEP observed via a series of in-vitro experiments using core (CoFe2O4)-shell (BaTiO3) structured magnetoelectric nanoparticles and human epithelial cells (HEP2). The cell electroporation phenomenon and its correlation with the magnetic field modulated CSMEN are described in detail. The potential application of CSMEN in electroporation is confirmed by analyzing crystallographic phases, multiferroic properties of the fabricated CSMEN, influences of d.c. and a.c. magnetic fields on the CSMEN and cytotoxicity tests. The mathematical formalism to quantitatively describe the phenomena is also reported. The reported findings provide insights into the underlying MEEP mechanism and demonstrate the utility of CSMEN as an electric pulse-generating nano-probe in electroporation experiments with a potential application toward accurate and efficient targeted cell permeation.

The ability to produce nanoparticles free of any surface contamination is very challenging especially for bio-medical applications. Using a pulsed nanosecond Nd-YAG laser, pure selenium nanoparticles have been synthesized by irradiating selenium powder (99.999%) immerged in de-ionized water and ethanol. The wavelength of the laser beam has been varied from the UV to NIR (355, 532 and 1064 nm) and its effect on the particle size distribution has been studied by dynamic light scattering (DLS) and transmission electronic microscopy (TEM), revealing then the production of selenium quantum dots (size < 4 nm) by photofragmentation. It has been found that the crystallinity of the nanoparticles depends on their size. The zeta-potential measurement reveals that the colloidal solutions produced in de-ionized water were stable while the ones synthesized in ethanol agglomerate. The concentration of selenium has been measured using inductively coupled plasma mass spectrometry (ICP-MS). The anti-bacterial effect of selenium nanostructures has been analyzed on E. Coli bacteria. Finally, selenium quantum dots produced by this method can also be useful for quantum dot solar cells.

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