Magnetic composite particles, method for manufacturing the same, and immunoassay particles

Magnetic composite particles in which an outer shell is formed on the surfaces of the core particles containing an inorganic oxide or a polymer,

• wherein the outer shell comprises magnetic nanoparticles and a layer of a silicon compound,
• wherein the value of a volume average particle diameter (dTEM) of the magnetic composite particles measured by a transmission electron microscope is 30 nm or more to 210 nm or less, and the magnetic composite particles can be reversibly controlled to a cluster state or a dispersion state by application or removal of a magnetic field,
• wherein the magnetic composite particles exhibit a saturation magnetization of 30 Am2/kg to 200 Am2/kg, and
• wherein the layer of the silicon compound comprises tetraethylorthosilicate (TEOS) and a silane coupling agent, wherein the silane coupling agent is 3-methacryloxy propyltrimethoxysilane (MPTMS).

Magnetic composite particles in which an outer shell is formed on the surfaces of the core particles containing an inorganic oxide or a polymer,

• wherein the outer shell comprises magnetic nanoparticles and a silicon compound,
• wherein the value of a volume average particle diameter (dTEM) of the magnetic composite particles measured by a transmission electron microscope is 30 nm or more to 210 nm or less,
• wherein the magnetic composite particles are subjected to a magnetic field,
• wherein a cluster state of the magnetic composite particles is a strand-shaped cluster state, and
• wherein the silicon compound comprises tetraethylorthosilicate (TEOS) and a silane coupling agent, wherein the silane coupling agent is 3-methacryloxy propyltrimethoxysilane (MPTMS).

A method for manufacturing the magnetic composite particles comprising:

• producing a suspension of magnetic nanoparticles;
• producing core particles comprising an inorganic oxide or a polymer, and having a value of a volume average particle diameter measured from a transmission electron microscope image of 20 nm or more to 200 nm or less,
• adding the core particles to the suspension of the magnetic nanoparticles and producing a suspension of heteroaggregation particles,
• adding an aqueous solution of a silicon compound to the suspension of the heteroaggregation particles, thereby providing a layer of the silicon compound on the surfaces of the heteroaggregation particles, and producing a suspension of the magnetic composite particles in which a value of a volume average particle diameter (dTEM) measured from a transmission electron microscope image is 30 nm or more to 210 nm or less, and
• wherein the layer of the silicon compound comprises tetraethylorthosilicate (TEOS) and a silane coupling agent, wherein the silane coupling agent is 3-methacryloxy propyltrimethoxysilane (MPTMS).