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Synthesis, size-sorting and surface modification of magnetic nanoparticles

Paweł G. Krysiński ,  P. Majewski 

Warsaw University, Faculty of Chemistry, Pasteura 1, Warszawa 02-093, Poland


The magnetic ferrite nanoparticles are recently in focus of modern science and biotechnology due to their unique properties, giving them a variety of possible applications, including targeted drug delivery. Colloidal ferrites are usually synthesized in a relatively simple aqueous precipitation reaction, which can be easily adapted for big-scale preparations. However, the main disadvantage of this route is the high polydispersity of the product, unsatisfactory for further practical applications. Here, we propose an efficient way of sorting the particles by size. The colloidal suspension of nanoparticles is centrifuged at increasing rotational speed and the fraction sedimented on the bottom of the tube is collected after each run. The particles’ size distribution and the efficiency of the process is estimated by agarose gel electrophoresis. Quantitatively, the mean size in each fraction is measured by Small Angle X-Ray Scattering and Powder X-Ray Diffraction.



Fig.1. Top: Powder XRD patterns of samples collected at increasing centrifugal forces. Widening of the peaks is observed.  Crystallite size calculated from PXRD peak broadening for the unsorted sample: 14 +/- .5 nm.

 Sorted particles are further subjected to chemical modifications of their surface including, in the first step, the adsorption of simple surfactant molecules and/or growth of the colloidal silica layer. Two-dimensional arrays, (on aqueous subphase, Langmuir-type) of particles grafted with oleic acid are transferred onto the solid substrate by Langmuir-Blodgett technique.  Subsequently, they were characterized by neutron and X-ray reflectivity as well as IR spectroscopy. The second step includes the covalent attachment of drug molecules (e.g., anthraquinone derivatives) to the particle surface coated with silica. Magnetic properties allow for targeted medicine delivery while silica coating prevents the heavy-metal containing core from direct contact with the organism thus providing higher biocompatibility of these carriers.


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Related papers

Presentation: Keynote lecture at SMCBS'2007 International Workshop, by Paweł G. Krysiński
See On-line Journal of SMCBS'2007 International Workshop

Submitted: 2007-08-14 10:48
Revised:   2009-06-07 00:44