Drug – bio-affecting and body treating compositions – In vivo diagnosis or in vivo testing – Magnetic imaging agent
Patent
1997-06-25
2000-04-11
Hollinden, Gary E.
Drug, bio-affecting and body treating compositions
In vivo diagnosis or in vivo testing
Magnetic imaging agent
424 932, 424646, 424648, 514 6, 514 54, 514 59, 514 60, A61B 5055
Patent
active
060485159
DESCRIPTION:
BRIEF SUMMARY
This invention relates to iron-containing nanoparticles having a modular structure, their production, and their use for diagnostic and therapeutic purposes.
Substances that show maximum magnetization even at a low field strength (high saturation magnetization) but no remanence after the external magnetic field is switched off, as the thermal energy counteracts the permanent alignment of spontaneously magnetized Weiss' domains, are called superparamagnetic substances. This category includes iron-containing crystals that are developed as parenteral MR contrast materials. A characteristic property of said substances is their strong impact on proton relaxation times and thus their great efficacy as a contrast medium in this diagnostic procedure. In medical diagnostics, the focus of examining superparamagnetic substances was placed on iron oxides having a "magnetite-like", crystal structure of the kind found in magnetite or maghemite (spinel, inverse spinel).
The superparamagnetic iron oxides to be used as MR contrast materials have similar properties in that they strongly influence proton relaxation in their close range (high relaxivity), and that they are particles having a "magnetite-like" crystal structure.
A great number of methods have been described for the production of iron-containing crystals (iron oxides) having superparamagnetic properties. These methods can be classified according to various aspects. Two basic methods to produce superparamagnetic crystals can be distinguished between: sintering at high temperatures and subsequent mechanical comminution, or wet chemical synthesis in solution. Up to now, only those particles that were produced by wet synthesis have been investigated for medical applications, while the sintering method has been described for the manufacture of iron oxides for technological (sound carriers, paint pigments and toners) and biotechnological applications such as the magnetic separating method [Schostek S., Beer A.; DE 3,729,697 A1; Borelli N. F., Luderer A. A., Panzarino J. N.; U.S. Pat. No. 4,323,056; Osamu I., Takeshi H., Toshihiro M. et al.; JP 60,260,463 A2]. Wet chemical synthesis can be subcategorized. There is "two-pot synthesis", which first produces an iron-containing core (iron oxide) to which a stabilizer is added to ensure the physical and galenic quality. The production of an iron core using ion exchangers is a variant of "two-pot synthesis". With "single-pot synthesis", the iron oxides are produced in the presence of the stabilizer which already coats the cores during nucleation and precipitation of the iron salts, thereby preventing aggregation and sedimentation of the nanocrystals.
Apart from distinguishing "two-pot" and "single-pot" methods according to the processes involved, there is another distinction based on the type of solvent used, namely between aqueous [Hasegawa M., Hokukoku S.; U.S. Pat. No. 4,101,435; Fuji Rebio K. K.; JP 59,195,161] and non-aqueous methods [Porath J., Mats L.; EP 179,039 A2; Shigeo A., Mikio K., Toshikatzu M.; J. Mater. Chem. 2(3); 277-280; 1992; Norio H., Saturo O.; JP 05,026,879 A2].
Particles that were produced in a "two-pot" process using non-aqueous solvents are mainly used in engineering. Magnetic iron oxides for use as contrast materials in human diagnostics require an aqueous dispersing agent for medical and toxicological reasons. A special place is held in this categorization by those particles that were produced in a non-aqueous solvent but can be stable when dispersed in an aqueous medium after production. Such particles are currently used, in general, in ex-vivo diagnostics, e.g. in magnetic separation engineering [Chagnon M. S., Groman E. V., Josephson L., et al.; U.S. Pat. No. 4,554,088] but have also been proposed for in-vivo diagnostics [Pilgrimm H.; U.S. Pat. No. 5,160,725].
Particles produced in a "two-pot" process were mainly used in the early experimental examinations up to the mid-1980s, while today's tests involving iron oxides are described only for materials produced by a "single-pot synthesis". The "si
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Ebert Wolfgang
Elste Volker
Gaida Josef
Herrmann Anja
Jukl Monika
Der Freien Universitat Berline
Hollinden Gary E.
Institut fur Diagnostikforschung GmbH
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