US20100063263A1 - Magnetic particles with a closed ultrathin silica layer, method for the production thereof and their use - Google Patents

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

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US20100063263A1
US20100063263A1 US11/917,922 US91792206A US2010063263A1 US 20100063263 A1 US20100063263 A1 US 20100063263A1 US 91792206 A US91792206 A US 91792206A US 2010063263 A1 US2010063263 A1 US 2010063263A1
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magnetic particles
silica
particles
nucleic acids
silicate
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Guido Hennig
Karlheinz Brand
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Siemens Healthcare Diagnostics GmbH Germany
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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N15/00—Mutation or genetic engineering; DNA or RNA concerning genetic engineering, vectors, e.g. plasmids, or their isolation, preparation or purification; Use of hosts therefor
    • C12N15/09—Recombinant DNA-technology
    • C12N15/10—Processes for the isolation, preparation or purification of DNA or RNA
    • C12N15/1003—Extracting or separating nucleic acids from biological samples, e.g. pure separation or isolation methods; Conditions, buffers or apparatuses therefor
    • C12N15/1006—Extracting or separating nucleic acids from biological samples, e.g. pure separation or isolation methods; Conditions, buffers or apparatuses therefor by means of a solid support carrier, e.g. particles, polymers
    • C12N15/1013—Extracting or separating nucleic acids from biological samples, e.g. pure separation or isolation methods; Conditions, buffers or apparatuses therefor by means of a solid support carrier, e.g. particles, polymers by using magnetic beads
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12Q—MEASURING OR TESTING PROCESSES INVOLVING ENZYMES, NUCLEIC ACIDS OR MICROORGANISMS; COMPOSITIONS OR TEST PAPERS THEREFOR; PROCESSES OF PREPARING SUCH COMPOSITIONS; CONDITION-RESPONSIVE CONTROL IN MICROBIOLOGICAL OR ENZYMOLOGICAL PROCESSES
    • C12Q1/00—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions
    • C12Q1/68—Measuring or testing processes involving enzymes, nucleic acids or microorganisms; Compositions therefor; Processes of preparing such compositions involving nucleic acids
    • C12Q1/6806—Preparing nucleic acids for analysis, e.g. for polymerase chain reaction [PCR] assay
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/12—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials
    • H01F1/34—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials non-metallic substances, e.g. ferrites
    • H01F1/36—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of soft-magnetic materials non-metallic substances, e.g. ferrites in the form of particles
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
    • H01F41/005—Impregnating or encapsulating
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F1/00—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
    • H01F1/01—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials
    • H01F1/03—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity
    • H01F1/032—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials
    • H01F1/10—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure
    • H01F1/11—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure in the form of particles
    • H01F1/112—Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties of inorganic materials characterised by their coercivity of hard-magnetic materials non-metallic substances, e.g. ferrites, e.g. [(Ba,Sr)O(Fe2O3)6] ferrites with hexagonal structure in the form of particles with a skin

Definitions

  • molecular diagnostics have become increasingly important.
  • Molecular diagnostics have entered into the clinical diagnosis of illnesses. This includes the measurement of molecular markers to improve the diagnosis of a disease, early detection, the monitoring of an illness during therapy, the prognosis of illnesses and the prediction of effects or side-effects of medicines (including the detection of infective agents, detection of mutations of the genome, the prediction of effects and side-effects of medicines on the basis of predetermined genetic patterns or those acquired in the course of an illness, detection of circulating tumor cells and the identification of risk factors for predisposition to an illness).
  • Methods of molecular diagnosis have meanwhile also been used in veterinary medicine, analysis of the environment and foodstuff testing.
  • a further application area is investigations by pathological/cytological institutes or in the course of forensic investigations. Genetic diagnosis has meanwhile also been used as part of healthcare (e.g. investigation of banked blood for freedom from infective agents), and legislation is planned to regulate such tests. Methods which are also used in clinical molecular diagnosis (such as hybridization or amplification techniques such as PCR (polymerase chain reaction), TMA (transcription mediated amplification), LCR (ligase chain reaction), bDNA (branched DNA) or NASBA (nucleic acid sequence based amplification) also form part of routine procedures in basic scientific work.
  • PCR polymerase chain reaction
  • TMA transcription mediated amplification
  • LCR ligase chain reaction
  • bDNA branched DNA
  • NASBA nucleic acid sequence based amplification
  • a precondition for performing an assay in molecular diagnostics is generally the isolation of DNA or RNA from the sample to be analyzed.
  • analysis methods such as bDNA-based tests that enable nucleic acid isolation and detection reaction to be carried out at the same time but PCR, as the most widely used molecular biological method in molecular diagnostics, almost always requires the use of previously purified nucleic acids because of their capacity to be influenced by exogenic factors.
  • the conventional preparation process for nucleic acids is in this case based on a fluid-fluid extraction.
  • An example of this is the phenol-chloroform extraction of DNA from body samples.
  • the great effort required and the need to sometimes perhaps use highly toxic substances means that this method has fallen considerably into disfavor in recent years compared with solid-phase based methods.
  • the sample preparation can be subdivided into the actual analysis operation, largely independent of the particular problem, into four basic steps: 1. Conditioning of the solid phase; 2. Selective or specific bonding of the analytes to the solid phase and removal of the remaining sample matrix; 3. Washing out any impurities from the solid phase and 4. Elution of the enriched and purified analytes.
  • nucleic acids to bond specifically to silicate-containing adsorbents such as glass powder [Proc. Natl. Acad. USA 76 (1979) 615-619, Anal. Biochem. 121 (1982) 382-387], diatomaceous earth [Methods Enzymol. 65 (1979) 176-182] or native silicon dioxide [J. Clin. Microbiol. 28 (1990) 495-503, EP 0 389 063 B1] under chaotropic or high-salt conditions, i.e. at high concentrations of chaotropes or other salts, has long been used for the selective and reversible bonding of nucleic acids.
  • silicate-containing adsorbents such as glass powder [Proc. Natl. Acad. USA 76 (1979) 615-619, Anal. Biochem. 121 (1982) 382-387], diatomaceous earth [Methods Enzymol. 65 (1979) 176-182] or native silicon dioxide [J. Clin.
  • a buffer containing water-soluble organic solvent usually a low aliphatic alcohol
  • impurities are then washed from the adsorbent, the carrier is dried and the adsorbed nucleic acids are eluated with distilled water or a so-called low-salt buffer, i.e. a buffer with a low ion strength.
  • magnetic particles of Fe 3 0 4 for electrographic toner with primary particle sizes of approximately 0.1 to 1 ⁇ m, e.g. available from the Lanxess company under the name Bayoxide E, meet almost ideal preconditions with regard to particle size.
  • particle sizes enable the important boundary condition of “suspension stability” important for biological applications to be achieved. This must on the one hand be sufficiently resistant to ensure that no significant sedimentation occurs within a few minutes, for example ten to fifteen minutes (adsorption of nucleic acids) after shaking, whereas the magnetic particles loaded with nucleic acids must be able to be completely separated as regards the shortest possible analysis times within a few minutes, for example within one to five minutes.
  • some magnetic particles produced on a large technical scale for example the Bayoxide E series from the Lanxess company, still have a certain nucleic acid bonding capacity even without special silica post-treatment, because they are produced in bulk and therefore also support SiOH groups on the surface in small amounts. Because of the low nucleic acid adsorption capacity, such products require corresponding relatively large amounts of magnetic particles, which means that the preparation of small sample volumes is hampered.
  • vessel walls such as glass or plastic walls of microtiter plates such as are routinely used for nucleic acid purification, that is unfavorable for the application described here. Therefore substantial amounts of the unmodified, relatively hydrophobic magnetic particles remain adsorbed in aqueous suspensions on the microtiter plate walls and thus lead to inaccuracies in pipetting and loss of yield.
  • Particles with a high density of SiOH surface groups which because of their hydrophilicity very advantageously roll off plastic walls in particular, such as the aforementioned microtiter plates, behave very favorably in this respect.
  • silica proportion is accordingly dominant compared with the magnetite proportion.
  • silica particles that can be magnetized by the magnetite inclusion are obtained by hydrolysis from reactive silica compounds such as tetraethoxysilane (TEOS) in the presence of magnetite particles.
  • TEOS tetraethoxysilane
  • the magnetic silica particles produced in this way have significantly more unfavorable morphological properties, such as very heterogeneous particle sizes and particle size distribution and it should be mentioned that large non-spherical particles can lead to blockages during automatic pipetting.
  • the nucleic acids isolated using the magnetic particle process are generally subject to further processes such as a PCR (polymerase chain reaction), TMA (transcription mediated amplification), LCR (ligase chain reaction) or NASBA (nucleic acid sequence based amplification).
  • PCR polymerase chain reaction
  • TMA transcription mediated amplification
  • LCR ligase chain reaction
  • NASBA nucleic acid sequence based amplification
  • the magnetic particles produced for the nucleic acid purification must fulfill particular purity requirements. If iron oxides, such as Bayoxide from the Lanxess company produced using technical mass production, are used this problem is certainly not insignificant because the magnetite particles have a certain porosity and surface roughness. Therefore, impurities can become included in the micropores both from the process of iron oxide production and in the succeeding silica treatment that as enzyme toxins or in the case of colored impurities can interfere with the photometric evaluation during subsequent processes.
  • the object of this invention is to produce, on the basis of commercially available magnetic particles, silica-modified magnetic particles with a high density of SiOH surface groups and a closed and tight surface layer of silicate. Neither the morphology nor the very good magnetic properties of the initial products should be substantially influenced by the silica modification. Equally, the wetting behavior on plastic surfaces should be positively influenced by the silica coating. Furthermore, the silica-modified magnetic particles should be optimized with regard to extractable impurities to the extent that the release of impurities or iron compounds from the magnetite core is prevented and no interference is possible with either the biological detection reactions or the photometric evaluation.
  • WO 03/058649 describes a smart process for silica deposition on the particle surface using sodium silicate solutions, for example sodium silicate HK 30 from the Cognis company.
  • sodium silicate solutions for example sodium silicate HK 30 from the Cognis company.
  • silica-modified magnetic particles described in WO 03/058649 have good properties with regard to surface structure and nucleic acid bonding behavior, very disadvantageous yellow-brown supernatants can be observed in the long-term behavior (after standing for a few weeks) of the relevant aqueous suspensions. In biological assays during which surfactants are generally used, this effect can be observed even after short stand times. An analysis shows that, in addition to sodium silicate components, traces of iron compounds and very fine magnetite particles can be found in these colored supernatants. Clearly, these impurities became locked into the porous magnetic particle structure through the silica surface, from where they diffuse outwards in the course of time. These observations also indicate that the silicate layer is not completely closed or is irregularly distributed by the batch method described in WO 03/058649 and therefore cannot prevent the release of iron compounds.
  • Bayoxide E 8707 with a pH of 6.5 has a slightly acid surface, a neutral pH value, or depending on the batch even a slightly alkali value (pH 7.5), is found with the Bayoxide E 8706 now used. Surprisingly, it was found that even these slightly alkali surface properties can induce sodium silicate deposition. Normally, the silica deposition takes place from the very alkali sodium silicate solutions by the addition of acids.
  • silica-modified magnetic particles produced in this way have a novel, i.e. ultrathin, silica structure on the silica surface, with which the improved purification or increased purity can be correlated.
  • This silica nanolayer is characterized by a silica layer of up to 5 nm distributed uniformly over the complete particle surface.
  • the method according to the invention however also describes a layer thickness of 2 nm and also, quite particularly preferred, layer thicknesses of 0.5 nm to 0.2 nm.
  • the particles coated in this way have a surface coating which is characterized in that it, for example, prevents the escape of irons into the surrounding solution.
  • the inventive method is characterized by a closed and tight silica layer, which is also associated with the improved purity or reduced observed contamination effect in the supernatant.
  • the purity of these silica-coated magnetic particles produced according to the inventive method is substantially better compared with the method described in WO 03/058649.
  • visible discoloration of the supernatant after production and washing no longer occurs (see examples 2 and 3).
  • the tight and closed silica layer prevents the escape of visible, or also invisible, impurities, for example iron ions, which can disturb the amplification methods or the optical evaluation of biological experiments (see examples 4 and 5).
  • magnetic particles coated with silica includes magnetite cores that are coated with a nanolayer of silica.
  • closed and tight silica layer includes a uniform, homogenous single to multiple molecular silica layer in a range of less than 5 nm, with a layer thickness of 2 nm being particularly preferred and a layer thickness of 0.5 to 0.2 nm being quite particularly preferred. This closed silica layer particularly prevents the release of iron compounds and iron ions to the environment of the silica-coated magnetic particle.
  • the expression “improved methods of production” includes a washing process with the aid of a micro- or ultra-filtration unit that is easy to perform but is very intensive and leads to extreme purity of the silica-coated magnetic particle.
  • a slow, controlled and continuous dilution, and therefore a reduction of the pH value to neutral pH values in the reaction solution occurs after an initial precipitation of the nanolayer of silicate onto the particle surface, thus forming an extremely uniform, tight, closed and homogenous layer of silicate on the surface of the magnetite.
  • unwanted formations of aggregates or clusters of silicates are prevented or largely reduced.
  • the expression “depletion of nano particulate components with the aid of the centrifugation technique” includes the application of centrifugation techniques or simple gravitational techniques. This produces sedimentation of the required fractions, with it being possible to reject the unwanted nano particulate components by removing the supernatant. By determining the particle size distribution using ultra-centrifugation, this effect can be detected by means of the depleted minute fractions.
  • the centrifugation technique With the centrifugation technique, the initial suspension is centrifuged for fifteen minutes at approximately 3000 g, the supernatant is removed and an equal amount of water or buffer is added and then re-suspended and this step is repeated several times (up to ten times).
  • the gravitation technique simply means that instead of the centrifugation a long time is allowed to elapse until a large proportion of the particles has settled on the bottom of the vessel and the aqueous supernatant is then replaced.
  • optimum magnetization behavior includes the property of the inventive particles to have the largest possible amount of magnetite and thus be completely separated from the sample matrix during the purification within a few minutes, for example within one to five minutes, when a magnetic field is applied from outside to a reaction vessel. This is particularly noteworthy with respect to the shortest possible purification times in an automated process using a pipetting robot and for the use of the cheapest possible magnets with a limited magnetic field strength as hardware components.
  • suspension behavior includes the property of the inventive particles to behave in such a way that due to an optimum grain size distribution no significant sedimentation occurs within a few minutes, for example ten to fifteen minutes (adsorption phase of the nucleic acids) after shaking during the purification phase.
  • the expression “optimum run-off behavior from plastic surfaces” includes the property the inventive particles have of a low affinity to the plastic articles used in biological purification processes due to a hydrophilic surface quality.
  • the plastic articles used mainly include polystyrene, polyethylene and polypropylene vessels or “microtiter” plates of comparable plastics of any shape or size.
  • the specific silica layer of the inventive magnetic particles enables a repelling interaction with these plastic surfaces, so that the coated magnetic particles roll off these surfaces and undergo no great interactions, which in the end could lead to a loss of yield during a biological purification process of nucleic acids.
  • isolation means the purification of nucleic acids from a biological sample using the aforementioned silica-coated magnetic particles and is divided into the following steps.
  • automated purification includes variations of these processes in which the manual labour by humans is replaced either completely or only partially in steps, especially with the biological body sample being dissolved with a special buffer during the steps, the addition of magnetic particles, the incubation at a specific temperature, the removal of non-absorbed sample constituents, the washing steps, the elution of bonded nucleic acids from the particles at a specific temperature and the separation of the eluate from the particle suspension.
  • nucleic acids includes oligomer and polymer ribonucleotides or 2′-desoxy-ribonucleotides with a chain length of more than 10 monomer units.
  • the monomer units in nucleic acids are linked by phosphoric acid diester compounds between 3′- and 5′-hydroxyl groups of adjacent monomer units and the 1′-atom of the respective carbohydrate component is glycosidically bonded to a heterocyclic base.
  • Nucleic acids can form double and triple strands due to the development of intermolecular hydrogen bridge bonds.
  • This also includes protein/nucleic acid complexes and nucleic acids with synthetic nucleotides such as morpholinos or PNAs (peptide-nucleic acids).
  • biological body sample includes biological material containing nucleic acid, such as whole blood, blood serum or blood plasma, especially serum or plasma containing a virus, very particularly serum samples infected with HIV and HCV, “Buffy Coat” (white blood cell fraction of the blood), faeces, ascites, swabs, sputum, organ aspirates, biopsies, tissue sections, in this case very particularly differently fixed tissue sections, especially those fixed with fixing agents containing formalin, and paraffin-embedded tissue sections, secretions, liquor, bile, lymphatic fluid, urine, stool, sperm, cells and cell cultures.
  • This can also include nucleic acids that originate from biochemical processes and are then to be purified.
  • the expression “detection with various amplification methods” includes the duplication of purified nucleic acids using various molecular-biological technologies, especially PCR, transcription-mediated amplification (TMA), LCA or also NASBA and the succeeding or simultaneous detection of the amplification products. This also includes detection using signal amplification methods such as of bDNA, i.e. without nucleic acid amplification. Detection of the PCR in particular can be carried out by the application of kinetic methods with the aid of fluorescence technology under real-time conditions or can be carried out using a conventional agarose gel. The real-time PCR in particular enables a very good quantitive determination of nucleic acids by using suitable calibrators. What is critical and limiting for clinical sensitivity (avoidance of false negative results) in this case is the efficient purification of the nucleic acids (i.e. efficient bonding to the magnetic particle and the reversible release under PCR-compatible conditions).
  • a further object of the invention is a kit for performing a method according to the invention that contains the following components:
  • This invention thus represents an important contribution to nucleic acid diagnostics.
  • Exact reaction conditions for the respective nucleic acids to be purified are given in these examples, but nevertheless various parameters such as magnetic particle quantity, incubation temperature and washing temperature, incubation and washing times and the concentration of lysis buffer, washing buffer and elution buffer can vary depending on the particular nucleic acid to be purified.
  • the stirrer After the stirrer is switched off, the silica-coated magnetite beads settle. This process can be accelerated if necessary by applying a magnetic field. After a waiting time of one hour, the supernatant is drawn off. For purification, 4 l of water is added whilst stirring for approximately ten minutes. The supernatant is again drawn off. This washing process is repeated at least four times until the last wash water has achieved a pH value of 7.5-7.0.
  • Example 1 The reaction part described in Example 1 was repeated but the processing took place not gradually or batchwise but instead with the aid of the “Centramate®” micro filtration unit from PALL with a 0.2 ⁇ m Supor® membrane cassette.
  • the magnetic particle suspension was drawn off via a hose by means of a pump and passed through the membrane cassette, with the permeate being rejected but the retentate being fed back into the reaction vessel. The amount equivalent to the permeate was then resupplied to the particle suspension.
  • the particle suspension purified by ultrafiltration showed no discoloration in the supernatant even after standing for several months at room temperature.
  • Example 2 The end product described in Example 2 was centrifuged for seven minutes at 3225g with the aid of a centrifuge (Eppendorf 5810). Whereas the main part (>98%) of the product was sedimented, a dark brown colored supernatant remained that was discarded.
  • the aqueous supernatants of the silica-coated magnetic particles HIE13266 had an absorption behavior similar to water.
  • the absorption lines of the supernatants of HIE12106R2 showed a clearly changed and elevated absorption behavior up to a range of approximately 500 nm.
  • aqueous supernatants of the two differently silica-coated magnetic particles were processed using magnetization.
  • Particle lot HIE13266 was produced using the inventive production method with continuous washing in a microfiltration unit (see Examples 2 and 3).
  • Particle lot HIE12106R2 was produced by repeated sequential washing (see WO 03/058649 A1) based on Bayoxide E 8707. Both supernatants were then subjected to a quantitive RT-PCR intervention:
  • the so-called quantitative RT (reverse transcription)-PCR intervention was carried out on the MX 4000 from Stratagene. As part of this, 5 ⁇ l of the supernatants of both of the particle supernatants, and 5 ⁇ l of water as a control, was added to 20 ⁇ l of Mastermix. This contains the following components: 400 nM Primer A, 400 nM Primer B, 10 ng MCF-7 RNA (Ambion), Taqman Primer 200 nM, 1 ⁇ Buffer A, 5 mM MgCl 2 ; 1.2 mM dNTPs, 8 U RNaseInhibitor, 20 U MuLV Reverse Transcriptase, 1.25 U Taq Gold (all from Applied Biosystems). The PCR program was: 30 min at 45° C., 10 min at 95° C., 45 cycles of 15 seconds at 96° C., 60 seconds at 63° C. and 30 sec at 72° C.
  • the preparations were placed in a 96-well microtiter plate (Stratagene), sealed and placed in the analysis device.
  • an individual C 1 value (number of cycle at which the selected base value intersects the amplification curve) was assigned to each sample at a selected basic value (fluorescence intensity) in the exponential amplification range of the signal curves.
  • the amplification curves with supernatants of particles HIE13266 are comparable with the amplification curves with water as a sample.
  • a shift of the amplification curves of approximately 3 C 1 values with supernatants from HIE12106R2 can be seen on the right-hand side, which indicates interference or negative influence on the efficiency of the RT-PCR.

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US11/917,922 2005-06-23 2006-06-13 Magnetic particles with a closed ultrathin silica layer, method for the production thereof and their use Abandoned US20100063263A1 (en)

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US20170159043A1 (en) 2017-06-08
US9617534B2 (en) 2017-04-11
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US10385331B2 (en) 2019-08-20
CN104810126A (zh) 2015-07-29
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EP1894214B1 (de) 2011-01-19
EP1894214B9 (de) 2018-05-23
ATE496380T1 (de) 2011-02-15
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US20150191718A1 (en) 2015-07-09

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