Magnetic particles with a closed ultrathin silica layer, method for the production thereof and their use

Abstract

The invention relates to magnetic particles coated with silica (Si02), whereby the silicate layer is closed and tight and is characterized by having an extremely small thickness on the scale of a few nanometers—hereafter also referred to as a silica nanolayer. This invention also relates to an improved method for producing these silicate-containing magnetic particles that, in comparison to the prior art, lead to a product having a closed silicate layer and thus entail a highly improved purity. In addition, the novel method prevents an uncontrolled formation of aggregates and clusters of silicates on the magnetite surface, thereby having a positive influence on the properties and biological applications cited below. The novel method also enables the depletion of nanoparticulate solid substance particles on the basis of a fractionated centrifugation. The inventive magnetic particles exhibit an optimized magnetization and suspension behavior as well as a very advantageous run-off behavior from plastic surfaces. These highly pure magnetic particles coated with silicon dioxide are preferably used for isolating nucleic acids from cell and tissue samples, whereby the separating out from a sample matrix ensues by means of magnetic fields. These particles are particularly well suited for the automatic purification of nucleic acids, mostly from biological body samples for the purpose of analyzing them with different amplification methods.

1 . Silica-coated magnetic particles, characterized in that they have a closed surface coating with silicate with a maximum layer thickness of 5 nm. 
   
   
       2 . The silica-coated magnetic particles as claimed in  claim 1  with a maximum layer thickness of silicate of 2 nm. 
   
   
       3 . The silica-coated magnetic particles as claimed in  claim 1  with a maximum layer thickness of silicate of 0.5 nm. 
   
   
       4 . The silica-coated magnetic particles as claimed in  claim 1 , with the magnetic material being iron oxide or magnetite. 
   
   
       5 . The silica-coated magnetic particles as claimed in  claim 4 , characterized in that the grain size distribution is between 0.1 and 1 μm. 
   
   
       6 . A method for the production of particles as claimed in  claim 1 , characterized in that the initial silicate deposition from sodium silicate or silica sol on the magnetic particles is triggered by the surface properties of the iron particles and the surface is then smoothed and sealed by slow, continuous dilution and reduction of the pH value to neutral pH values. 
   
   
       7 . The method for the purification of nucleic acids from biological body samples using magnetic particles as claimed in  claim 1 . 
   
   
       8 . The method as claimed in  claim 7 , characterized in that the nucleic acids are RNA or DNA. 
   
   
       9 . The method as claimed in  claim 7 , characterized in that it relates to RNA of HCV or HIV. 
   
   
       10 . The method as claimed in  claim 7 , characterized in that the RNA or DNA is from fixed body samples.