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      Magnetic Nanoparticles: Surface Effects and Properties Related to Biomedicine Applications

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          Due to finite size effects, such as the high surface-to-volume ratio and different crystal structures, magnetic nanoparticles are found to exhibit interesting and considerably different magnetic properties than those found in their corresponding bulk materials. These nanoparticles can be synthesized in several ways (e.g., chemical and physical) with controllable sizes enabling their comparison to biological organisms from cells (10–100 μm), viruses, genes, down to proteins (3–50 nm). The optimization of the nanoparticles’ size, size distribution, agglomeration, coating, and shapes along with their unique magnetic properties prompted the application of nanoparticles of this type in diverse fields. Biomedicine is one of these fields where intensive research is currently being conducted. In this review, we will discuss the magnetic properties of nanoparticles which are directly related to their applications in biomedicine. We will focus mainly on surface effects and ferrite nanoparticles, and on one diagnostic application of magnetic nanoparticles as magnetic resonance imaging contrast agents.

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          SENSE: Sensitivity encoding for fast MRI

          New theoretical and practical concepts are presented for considerably enhancing the performance of magnetic resonance imaging (MRI) by means of arrays of multiple receiver coils. Sensitivity encoding (SENSE) is based on the fact that receiver sensitivity generally has an encoding effect complementary to Fourier preparation by linear field gradients. Thus, by using multiple receiver coils in parallel scan time in Fourier imaging can be considerably reduced. The problem of image reconstruction from sensitivity encoded data is formulated in a general fashion and solved for arbitrary coil configurations and k-space sampling patterns. Special attention is given to the currently most practical case, namely, sampling a common Cartesian grid with reduced density. For this case the feasibility of the proposed methods was verified both in vitro and in vivo. Scan time was reduced to one-half using a two-coil array in brain imaging. With an array of five coils double-oblique heart images were obtained in one-third of conventional scan time. Magn Reson Med 42:952-962, 1999. Copyright 1999 Wiley-Liss, Inc.
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            In vitro cytotoxicity testing of polycations: influence of polymer structure on cell viability and hemolysis.

            A comparative in vitro cytotoxicity study with different water-soluble, cationic macromolecules which have been described as gene delivery systems was performed. Cytotoxicity in L929 mouse fibroblasts was monitored using the MTT assay and the release of the cytosolic enzyme lactate dehydrogenase (LDH). Microscopic observations were carried out as indicators for cell viability. Furthermore, hemolysis of erythrocytes was quantified spectrophotometrically. To determine the nature of cell death induced by the polycations, the nuclear morphology after DAPI staining and the inhibition of the toxic effects by the caspase inhibitor zVAD.fmk were investigated. All assays yielded comparable results and allowed the following ranking of the polymers with regard to cytotoxicity: Poly(ethylenimine)=poly(L-lysine)>poly(diallyl-dimethyl-ammonium chloride)>diethylaminoethyl-dextran>poly(vinyl pyridinium bromide)>Starburst dendrimer>cationized albumin>native albumin. The magnitude of the cytotoxic effects of all polymers were found to be time- and concentration dependent. The molecular weight as well as the cationic charge density of the polycations were confirmed as key parameters for the interaction with the cell membranes and consequently, the cell damage. Evaluating the nature of cell death induced by poly(ethylenimine), we did not detect any indication for apoptosis suggesting that the polymer induced a necrotic cell reaction. Cell nuclei retained their size, chromatin was homogenously distributed and cell membranes lost their integrity very rapidly at an early stage. Furthermore, the broad spectrum caspase inhibitor zVAD.fmk did not inhibit poly(ethylenimine)-induced cell damage. Insights into the structure-toxicity relationship are necessary to optimize the cytotoxicity and biocompatibility of non-viral gene delivery systems.
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              Theory of the Structure of Ferromagnetic Domains in Films and Small Particles


                Author and article information

                Int J Mol Sci
                Int J Mol Sci
                International Journal of Molecular Sciences
                Molecular Diversity Preservation International (MDPI)
                November 2013
                25 October 2013
                : 14
                : 11
                : 21266-21305
                [1 ]Department of Physics, College of Science, United Arab Emirates University, Al Ain, 15551, UAE; E-Mail: iobaidat@ 123456uaeu.ac.ae
                [2 ]Superconductivity & Magnetic Measurements Laboratory, Physics Department, Jordan University of Science and Technology, Irbid 22110, Jordan; E-Mail: baalbiss@ 123456just.edu.jo
                [3 ]Department of Mechanical Engineering, College of Engineering, United Arab Emirates University, Al Ain, 15551, UAE; E-Mail: yhaik@ 123456uaeu.ac.ae
                [4 ]Centre of Research Excellence in Nanobioscience 203, Eberhart Building University of North Carolina, Greensboro, NC 27412, USA
                Author notes

                These authors contributed equally to this work.

                [* ]Author to whom correspondence should be addressed; E-Mail: b.issa@ 123456uaeu.ac.ae ; Tel.: +971-3-713-6316; Fax: +971-3-713-6944.
                © 2013 by the authors; licensee MDPI, Basel, Switzerland

                This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license ( http://creativecommons.org/licenses/by/3.0/).



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