Abstract: The present invention relates to latex particles for measurement reagents, said latex particles having a coefficient of variation in particle diameters of 10% or less and an average particle diameter of 250 to 1000 nm. Each of the latex particles contains 20% by weight or more of a compound having a refractive index of 1.60 or more. The depth of a supernatant is 5 mm or less when a liquid dispersion having a solid matter concentration of 1% by weight, which is prepared by dispersing the latex particles in ultrapure water, is placed in a tubular 10-ml measuring cylinder having a body inner diameter of 10.8 mm and is then allowed to leave for 10 days. According to the particles, a measurement of a measurement sample can be performed at a high sensitivity even when the concentration of a substance to be tested in the measurement sample is low.

Abstract: Disclosed is a sensitized magnetic responsive particle including: a magnetic responsive particle having a core particle and at least one magnetic layer disposed on the core particle, the magnetic layer containing microparticles of a magnetic metal and/or an oxide thereof; and a substance that specifically interacts with an analyte, the substance being supported on the magnetic responsive particle, wherein, assuming that a volume and a weight of the core particle are respectively vc and wc, and that a volume and a weight of the magnetic responsive particle are respectively ve and we, the magnetic material density [(we?wc)/(ve?vc)] satisfies the following expression 1: 2.0?(we?wc)/(ve?vc) ??Expression 1 The magnetic responsive particle has a high magnetic collection property in spite of a small particle size. When the magnetic responsive particle is used, a reagent for an immunoassay having excellent magnetic separability and capable of realizing high sensitivity can be provided.

Abstract: Disclosed is a sensitized magnetic responsive particle including: a magnetic responsive particle having a core particle and at least one magnetic layer that is disposed on the core particle and includes microparticles of a magnetic metal and/or an oxide thereof; and a substance that is supported on the magnetic responsive Particle and interacts specifically with an analyte, wherein the coefficient of variation in the weight-average particle size of the magnetic responsive particles is 15% or less. The magnetic responsive particle provided has excellent magnetic separability.

Abstract: The present invention relates to latex particles for measurement reagents, said latex particles having a coefficient of variation in particle diameters of 10% or less and an average particle diameter of 250 to 1000 nm. Each of the latex particles contains 20% by weight or more of a compound having a refractive index of 1.60 or more. The depth of a supernatant is 5 mm or less when a liquid dispersion having a solid matter concentration of 1% by weight, which is prepared by dispersing the latex particles in ultrapure water, is placed in a tubular 10-ml measuring cylinder having a body inner diameter of 10.8 mm and is then allowed to leave for 10 days. According to the particles, a measurement of a measurement sample can be performed at a high sensitivity even when the concentration of a substance to be tested in the measurement sample is low.