Surface Study of Fe3O4 Nanoparticles Functionalized With Biocompatible Adsorbed Molecules.

Surfaces of iron oxide of ferrimagnetic magnetite (Fe3O4) nanoparticles (MNPs) prepared by Massart's method and their functionalized form (f-MNPs) with succinic acid, L-arginine, oxalic acid, citric acid, and glutamic acid were studied by dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR-S), UV-vis, thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS), and reflection electron energy loss spectroscopy (REELS). The XPS analysis of elements and their chemical states at the surface of MNPs and f-MNPs revealed differences in chemical bonding of atoms, content of carbon-oxygen groups, iron oxide forms, iron oxide magnetic properties, adsorbed molecules, surface coverage, and overlayer thickness, whereas the Auger parameters (derived from XPS and Auger spectra) and elastic and inelastic scattering probabilities of electrons on atoms and valence band electrons (derived from REELS spectra) indicated modification of surface charge redistribution, electronic, and optical properties. These modified properties of f-MNPs influenced their biological properties. The surfaces biocompatible for L929 cells showed various cytotoxicity for HeLa cells (10.8-5.3% of cell death), the highest for MNPs functionalized with oxalic acid. The samples exhibiting the largest efficiency possessed smaller surface coverage and thickness of adsorbed molecules layers, the highest content of oxygen and carbon-oxygen functionalizing groups, the highest ratio of lattice O2- and OH- to C sp2 hybridizations on MNP surface, the highest ratio of adsorbed O- and OH- to C sp2 hybridizations on adsorbed molecule layers, the closest electronic and optical properties to Fe3O4, and the lowest degree of admolecule polymerization. This high cytotoxicity was attributed to interaction of cells with a surface, where increased content of oxygen groups, adsorbed O-, and OH- may play the role of additional adsorption and catalytic sites and a large content of adsorbed molecule layers of carboxylic groups facilitating Fenton reaction kinetics leading to cell damage.

Surface plasmon excitations in cylindrical nanorods by electron-hole pair creation.

In this work we study the effect of the excitation of surface plasmons in a metallic cylindrical nanorod by a suddenly created electron-hole pair, using a classical model for the emerging electron and a quantum-mechanical model for the plasmon field in the cylinder. The electron and the hole interact independently with the plasmon field, generating electron density oscillations. Two different trajectories for the emerging electron (parallel to the axis and radial) are studied in an aluminum nanorod. The average number of excited plasmons indicates how important is the role of the hole in the excitation process. We found that the results can be very different according to the trajectory of the emerging electron. We also found that the distinction between intrinsic and extrinsic process is sometimes not applicable.

Urokinase-like plasminogen activators of unusually high molecular weight secreted by a cell line derived from a human lung cancer case.

The HPL-SK-1 cell line derived from the pleural exudate of a lung cancer patient has been shown to secrete plasminogen activators of very high molecular weights (greater than or equal to 2 and 1 million), as shown by gel filtration on Sepharose 6B or CL-6B. The size of these activators could not be reduced by chromatography in buffers containing 2% sodium dodecyl sulfate, 8 M urea, or 1 M KSCN. Goat anti-urokinase antibody inhibited these activators only partially. Trypsin digestion of the 2 million-dalton species yielded several active fragments including one of the size of urokinase, 55,000 daltons. These large activators could be purified only by a double antibody immunoadsorption technique which consisted of the formation of a soluble immune complex between the activators and goat anti-urokinase IgG, followed by the adsorption of this complex to rabbit anti-goat IgG coupled to Affi-Gel 10. The eluted activators were purified 50-fold (2 million daltons) and 130-fold (1 million daltons), respectively. Reduction of the two largest species in the presence of sodium dodecyl sulfate resulted in the appearance of smaller molecular weight active fragments of differing size, indicating that these activators are disulfide-linked oligomers. Among the fragments of the 2 million-dalton species was found a 10,000-dalton enzyme which had lost activator and antigenic specificity and retained only a non-specific protease activity. A similar fragment was also isolated from reduced, purified 55,000-dalton urinary urokinase.