Magnetic glass particles, method for their preparation and uses thereof

Abstract

This invention relates to magnetic particles having a glass surface which are substantially spherical. This invention also relates to methods for making them, as well as to suspensions thereof and their uses for the purification of DNA or RNA in particular in automated processes.

1 . A composition of magnetic glass particles 
 wherein 
 the magnetic glass particles comprise at least one magnetic object with a mean diameter between 5 to 500 nm.  
   
     
     
         2 . The composition of  claim 1   wherein 
 the magnetic object has a mean diameter between 10 to 200 nm, preferably between 15 to 50 nm.  
   
     
     
         3 . The composition of  claim 1   wherein 
 the half-life period for the sedimentation of a 3 mg/ml weight-per-volume suspension of the composition in isopropanol is more than 3 min.  
   
     
     
         4 . The composition of  claim 1   wherein 
 the half-life period is more than 6 min.  
   
     
     
         5 . The composition of  claim 1   wherein 
 the magnetic object has a mean diameter of 23 nm.  
   
     
     
         6 . The composition of  claim 1   wherein 
 the diameter ratio of the magnetic body to the glass shell is less than 1 to 10.  
   
     
     
         7 . The composition of  claim 1   wherein 
 the magnetic glass particles have a mean diameter between 0.5 μm and 5 μm.  
   
     
     
         8 . The composition of  claim 7   wherein 
 the magnetic glass particles have a mean diameter between 1 μm to 2 μm.  
   
     
     
         9 . The composition of  claim 1   wherein 
 the magnetic glass particles are microporous.  
   
     
     
         10 . The composition of  claim 1   wherein 
 the pore surface of the magnetic glass particles is less than 10% of the total surface.  
   
     
     
         11 . The composition of  claim 1   wherein 
 the magnetic object is superparamagnetic.  
   
     
     
         12 . The composition of  claim 1   wherein 
 the magnetic object is ferrimagnetic or ferromagnetic.  
   
     
     
         13 . The composition of  claim 1   wherein 
 the magnetic object comprises iron or iron oxide.  
   
     
     
         14 . The composition of  claim 13   wherein 
 the iron oxide is Fe 3 O 4  or γ-Fe 2 O 3 .  
   
     
     
         15 . The composition of  claim 1   wherein 
 the magnetic glass particles have a surface area of more than 4 m 2 /g.  
   
     
     
         16 . The composition of  claim 15   wherein 
 the magnetic glass particles have a surface area between 5 to 100 m 2 /g, preferably in the range of 10 to 50 m 2 /g, most preferably in the range of 15 to 30 m 2 /g.  
   
     
     
         17 . The composition of  claim 1   wherein 
 the magnetic glass particles are substantially spherical.  
   
     
     
         18 . A suspension comprising a composition of magnetic glass particles according to  claim 1  in a liquid.  
     
     
         19 . The suspension of  claim 18   wherein 
 the liquid comprises an alcohol.  
   
     
     
         20 . The composition of  claim 19   wherein 
 the alcohol is isopropanol or ethanol.  
   
     
     
         21 . The composition of  claim 19   wherein 
 the liquid is 70% (V/V) ethanol.  
   
     
     
         22 . The suspension of  claim 18   wherein 
 the liquid is a buffered aqueous solution.  
   
     
     
         23 . The suspension of  claim 22   wherein 
 the solution is buffered by Tris-hydroxymethylamine, phosphate, N-(2-Hydroxyethyl)piperazine-N′-(2-ethanesulfonic acid) or a salt thereof.  
   
     
     
         24 . The suspension of  claim 22   wherein 
 the solution further contains substances modifying the ionic strength or metal-complexing agents.  
   
     
     
         25 . The suspension of  claim 22   wherein 
 the suspension additionally contains DNA or RNA.  
   
     
     
         26 . The suspension of  claim 22   wherein 
 the suspension contains additionally DNA or RNA or both in a mixture with one or more compounds selected from the group of proteins, fatty acids, carbohydrates or any other biological material.  
   
     
     
         27 . The suspension of  claim 18   wherein 
 the suspension additionally contains a chaotropic agent.  
   
     
     
         28 . The suspension of  claim 27   wherein 
 the chaotropic agent is selected from the group consisting of sodium iodite, sodium perchlorate, guanidinium thiocyanate, guanidinium isothiocyanate or guanidinium hydrochloride.  
   
     
     
         29 . The suspension of  claim 27   wherein 
 the chaotropic agent is present in a concentration between 2 and 8 mol/l, and preferably between 4 and 6 mol/l.  
   
     
     
         30 . The suspension of  claim 18   wherein 
 the suspension contains 5 to 60 mg/ml of a composition of magnetic glass particles  
   wherein 
 the magnetic glass particles comprise at least one magnetic object with a mean diameter between 5 to 500 nm.  
   
     
     
         31 . A tube containing the composition of  claim 1 .  
     
     
         32 . A storage container containing the composition of  claim 1 .  
     
     
         33 . A kit of parts comprising the tube of  claim 1  or the storage container of  claim 1 .  
     
     
         34 . The kit of parts of  claim 1  further comprising a washing solution or an eluent.  
     
     
         35 . The kit of parts of  claim 1  further comprising reagents suitable for the purification of a nucleic acid.  
     
     
         36 . A tube containing the suspension of  claim 18 .  
     
     
         37 . A storage container containing the suspension of  claim 18 .  
     
     
         38 . A kit of parts comprising the tube of  claim 36  or the storage container of  claim 37 .  
     
     
         39 . A method for the production of a composition of magnetic glass particles comprising the steps of 
 a) suspending magnetic objects with a diameter between 5 and 500 nm in a sol,    b) spray-drying the suspension in a two-nozzle spray-drier, and    c) sintering the spray-dried powder.    
     
     
         40 . The method of  claim 39   wherein 
 the inlet temperature of the two-nozzle spray-drier is between 120° C. and 500° C.,  
 the outlet temperature is chosen according to the boiling point of the sol and the spray pressure is at least 3 bar.  
   
     
     
         41 . The method of  claim 39   wherein 
 the inlet temperature of the two-nozzle spray-drier is between 170° C. and 230° C., preferably between 190° C. and 210° C.  
   
     
     
         42 . The method of  claim 39   wherein 
 the inlet temperature of the two-nozzle spray-drier is 200° C.  
   
     
     
         43 . The method of  claim 39   wherein 
 the spray pressure is between 4 and 6 bar.  
   
     
     
         44 . The method of  claim 39   wherein 
 the sol contains ethanol as solvent.  
   
     
     
         45 . The method of  claim 44   wherein 
 the outlet temperature is between 50° C. and 300° C.  
   
     
     
         46 . The method of  claim 44   wherein 
 the outlet temperature is between 90° C. and 100° C.  
   
     
     
         47 . The method of  claim 39   wherein 
 the sinter temperature is between 400° C. to 1200° C., preferably between 720° C. and 770° C.  
   
     
     
         48 . The magnetic glass particles produced by the method of  claim 1 .  
     
     
         49 . A procedure for isolating a biological material comprising 
 a) contacting a sample that contains the biological material in a liquid with a composition of magnetic glass particles wherein the magnetic glass particles comprise at least one magnetic object with a mean diameter between 5 to 500 nm under conditions in which the biological material binds directly to the surface of the magnetic glass particles, and    b) separating the biological material from the liquid.    
     
     
         50 . The procedure of  claim 49  wherein the biological material is a nucleic acid.  
     
     
         51 . The procedure of  claim 49  wherein the biological material contains a mixture of nucleic acids, wherein the target nucleic acid or target nucleic acids is/are present in low abundance.  
     
     
         52 . The procedure of  claim 49  wherein 
 the separation is accomplished with the aid of a magnet.  
 
     
     
         53 . The procedure of  claim 49  wherein 
 the magnetic particles are not premagnetized when brought into contact with the sample.  
 
     
     
         54 . The procedure of  claim 49  wherein the procedure is automatized.  
     
     
         55 . The procedure of  claim 49  wherein 
 the procedure is in a high-throughput format.  
 
     
     
         56 . The procedure of  claim 49  wherein 
 during the procedure a suspension of magnetic glass particles, wherein the magnetic glass particles comprise at least one magnetic object with a mean diameter between 5 to 500 nm, is taken from a storage container and partial volumes of the suspension are added to different reaction vessels.  
 
     
     
         57 . The procedure of  claim 49  wherein 
 the nucleic acid is detected after the purification.  
 
     
     
         58 . The procedure of  claim 49  wherein the nucleic acid is detected after an amplification step.  
     
     
         59 . The procedure of  claim 57   wherein 
 the nucleic acid is detected by a process comprising: 
 a) contacting the sample with an oligonucleotide comprising a sequence complementary to a region of the target nucleic acid and a labeled oligonucleotide comprising a sequence complementary to a second region of the same target nucleic acid sequence strand, but not including the nucleic acid sequence defined by the first oligonucleotide, to create a mixture of duplexes during hybridization conditions, wherein the duplexes comprise the target nucleic acid annealed to the first oligonucleotide and to the labeled oligonucleotide such that the 3′-end of the first oligonucleotide is adjacent to the 5′-end of the labeled oligonucleotide;  
 b) maintaining the mixture of step a) with a template-dependent nucleic acid polymerase having a 5′ to 3′ nuclease activity under conditions sufficient to permit the 5′ to 3′ nuclease activity of the polymerase to cleave the annealed, labeled oligonucleotide and release labeled fragments; and  
 c) detecting and/or measuring the signal generated by the hydrolysis of the labeled oligonucleotide.  
 
   
     
     
         60 . The procedure of  claim 59   wherein 
 the detection is carried out in the presence of a blocking oligonucleotide.  
   
     
     
         61 . The procedure of  claim 60   wherein 
 the blocking oligonucleotide is an aptamer.  
   
     
     
         62 . The procedure of  claim 61   wherein 
 the aptamer has the sequence SEQ ID NO: 23.  
   
     
     
         63 . The procedure of  claim 60   wherein the amplification and detection reaction is carried out in a homogeneous solution-phase multiplex assay format for the simultaneous detection of multiple targets.    
     
     
         64 . The procedure of  claim 60   wherein for at least 5 cycles of the polymerase chain reaction, the annealing temperature is less than 8° C., preferably less than 3° C. above the dissociation temperature of the polymerase-aptamer complex.