Magnetic nanoparticles having improved magnetic properties
The invention relates to a method for producing magnetic nanoparticles which are made of metal oxide-polymer composites and are provided with an increased magnetic mobility, among other things, due the high metal oxide content and the morphological structure thereof. High-pressure homogenization has proven to be a reliable technique for producing the inventive magnetic nanoparticles. According to said technique, the components metal oxide and polymer are processed in a carrier medium. Water is used in most cases at pressures ranging from 500 bar to 1200 bar while using great shearing forces. High pressure homogenization creates a colloidally stable magnetic particle population having a diameter ranging below 200 nm while also resulting in the produced magnetic nanoparticles being provided with greater magnetic moments than the metal oxide used as an initial material at low magnetic field strengths. The inventive particles are particularly suitable for applications in the bioanalytical and diagnostic field, in bioseparation processes, and as a carrier material in high throughput screening.
1. Magnetic nanoparticles comprising iron oxide and a polymer and produced by subjecting the iron oxide and the polymer to high pressure homogenization in an aqueous medium, the nanoparticles comprising at least 50 mass percent iron, having hydrodynamic diameter of less than 200 nm and higher magnetization at low magnetic field strengths than the iron oxide from which the magnetic nanoparticles were produced.
2. Magnetic nanoparticles according to claim 1 , wherein the nanoparticles have the properties of forming in water or an aqueous solution a colloid which is stable for a long period in the absence of an external magnetic field.
3. Magnetic nanoparticles according to claim 1 , wherein the nanoparticles have the property of being separable by permanent magnets from a medium in which the nanoparticles are contained.
4. Magnetic nanoparticles according to claim 2 wherein the nanoparticles have the property of being separable from the water or the aqueous solution in which they have formed a colloid.
5. Magnetic nanoparticles according to claim 1 , wherein the iron oxide comprises magnetite or maghemite or a mixture of magnetite and maghemite.
6. Magnetic nanoparticles according to claim 5 , wherein the iron oxide or mixture of iron oxides contains at least one bivalent or trivalent metal ion other than iron ions.
7. Magnetic nanoparticles according to claim 1 , wherein the polymer comprises synthetic polymer.
8. Magnetic nanoparticles according to claim 1 , wherein the polymer comprises natural or derivatized polysaccharide.
9. Magnetic nanoparticles according to claim 8 , wherein the polysaccharide comprises dextrane.
10. Magnetic nanoparticles according to claim 9 , wherein the dextrane is derivatized with functional groups or substructures.
11. Magnetic nanoparticles comprising iron oxide and a polymer and produced by sequentially subjecting the iron oxide and a combination of iron oxide and polymer to high pressure homogenization in an aqueous medium, the nanoparticles comprising at least 50 mass percent iron, having hydrodynamic diameter of less than 200 nm and higher magnetization at low magnetic field strengths than the iron oxide from which the magnetic nanoparticles were produced, wherein the subjecting comprises the steps of:
providing an aqueous suspension of iron oxide in a high pressure homogenizer,
homogenizing the suspension of iron oxide in the high pressure homogenizer at a pressure of 500 bar,
combining an aqueous solution of a polymer with the homogenized suspension of iron oxide in the high pressure homogenizer,
homogenizing the resulting combination in the high pressure homogenizer at a pressure of 500 to 1200 bar to form a suspension of the magnetic nanoparticles, and
separating the magnetic nanoparticles from the suspension of magnetic nanoparticles under the action of a magnetic field.
12. The magnetic nanoparticles of claim 11 wherein the magnetic field in the separation step is provided by a permanent magnet.
13. Magnetic nanoparticles comprising iron oxide and a polymer and produced by subjecting the iron oxide to high pressure homogenization in an aqueous medium, the nanoparticles comprising at least 50 mass percent iron, having hydrodynamic diameter of less than 200 nm and higher magnetization at low magnetic field strengths than the iron oxide from which the magnetic nanoparticles were produced, wherein the subjecting comprises the steps of:
providing an aqueous suspension of iron oxide in a high pressure homogenizer,
homogenizing the suspension of iron oxide in the high pressure homogenizer at a pressure of 500 bar,
combining an aqueous solution of a polymer with the homogenized suspension of iron oxide in the high pressure homogenizer,
adjusting the pH of the combined aqueous suspension of iron oxide and aqueous solution of polymer by adding an alkaline substance to obtain the magnetic nanoparticles, and
washing the magnetic nanoparticles with water under the influence of a high gradient magnetic field.
14. The magnetic nanoparticles of claim 1 wherein the homogenization step is carried out at a pressure of 500 to 1200 bar.
15. The magnetic nanoparticles of claim 1 wherein the iron oxide is produced in situ in the aqueous medium, wherein the aqueous medium has a pH>7.
16. The magnetic nanoparticles of claim 15 wherein the aqueous medium comprises a solution of ammonia and water.