Aggregation and dispersion methods of magnetic particles, separation and detection methods using the same and detection kit

1. A method of separating a substance to be detected from a sample, comprising the steps of:

mixing an adsorbent and the sample in an aqueous solution to adsorb the substance to be detected on the adsorbent,

aggregating the adsorbent by changing a salt concentration in the aqueous solution at a given temperature without heating or cooling the aqueous solution; and

collecting the adsorbent from the aqueous solution by a magnetic force, wherein said adsorbent comprises a magnetic particle of an average particle size of 50 to 1000 nm, a surface of which is modified with a thermoresponsive polymer and is immobilized with a substance having an affinity for the substance to be detected.

2. The method according to claim 1 , wherein the thermoresponsive polymer is a polymer obtained by polymerization of at least one type of monomer selected from the group consisting of N-n-propylacrylamide, N-isopropylacrylamide, N-t-butylacrylamide, N-ethylacrylamide, N,N-dimethylacrylamide, N-acryloylpyrrolidine, N-acryloylpiperidine, N-acryloylmorpholine, N-n-propylmethacrylamide, N-isopropylmethacrylamide, N-ethylmethacrylamide, N,N-dimethylmethacrylamide, N-methacryloylpyrrolidine, N-methacryloylpiperidine and N-methacryloylmorpholine.

3. The method according to claim 1 , wherein the thermoresponsive polymer is a polymer obtained by polymerization of at least one type of monomer selected from the group consisting of N-acryloylglycinamide, N-acryloylnipecotamide and N-acryloylasparaginamide.

4. The method according to claim 1 , wherein the average particle size of the magnetic particle is from 50 to 200 nm.

5. The method according to claim 1 , wherein the salt contains at least one type of compound selected from the group consisting of lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate, ammonium sulfate, sodium carbonate and potassium carbonate.

6. The method according to claim 1 , wherein the salt contains at least one type of compound selected from the group consisting of a sodium monocarboxylate, a potassium monocarboxylate, a sodium dicarboxylate, a potassium dicarboxylate, a sodium tricarboxylate, a potassium tricarboxylate, a sodium tetracarboxylate and a potassium tetracarboxylate.

7. The method according to claim 6 , wherein the salt contains at least one type of compound selected from the group consisting of sodium acetate, sodium aspartate, disodium citrate, disodium ethylenediamine tetraacetate, sodium glutamate, sodium iminodiacetate, sodium maleate, sodium malonate, sodium oxalate, disodium succinate and sodium tartrate.

8. A kit for separating or detecting a substance to be detected in a sample, comprising an adsorbent and an aqueous salt solution but no heating or cooling means, wherein said adsorbent comprises a magnetic particle of an average particle size of 50 to 1000 nm, a surface of which is modified with a thermoresponsive polymer and is immobilized with a substance having an affinity for the substance to be detected.

9. A method of aggregating or dispersing magnetic particles, comprising the step of aggregating or dispersing magnetic particles having a surface modified with a thermoresponsive polymer, which are obtained by subjecting magnetic particles to surface modification with a thermoresponsive polymer, by changing a salt concentration in an aqueous solution at a given temperature without heating or cooling the aqueous solution.

10. The method according to claim 9 , wherein the magnetic particle having a surface modified with a thermoresponsive polymer has a substance having an affinity for a substance to be detected on its surface.

11. A method of detecting a substance to be detected in a sample, comprising the steps of:

separating the substance to be detected from the sample by adsorbing the substance to be detected on the adsorbent by the method according to claim 1 ; and

detecting the substance to be detected adsorbed on the adsorbent.