A new type of magnetic nanoparticles that are capable of constructing various types of functional proteins without damaging the activity have been developed for a wide range of applications such as analysis for gene function and research for lead compounds of medicinal products are revealed in U.S. Patent Application 20090325258.
Researchers at the Tokyo University of Agriculture and Technology (Fuchu-shi, JP) and Precision System Science Co,. Ltd (Matsudo-shi, JP) developed a process that makes it much easier to automatize a treatment with nano-size magnetic particles . This was achieved by fitting nano-size magnetic particles (about 1 nm to several 100 nm) such as bacterial magnetic particles produced by a magnetic bacterium, to a particulate carrier having a size on the order of micrometer (ranging from about 1 .mu.m to several 100 .mu.m) in accordance with the purpose of the treatment.
The magnetic particle holding carrier is formed of a micro-size nonmagnetic carrier and a plurality of nano-size magnetic particles bound to the carrier. Tadashi Matsunaga, Haruko Takeyama, Tomoko Yoshino and Hideji Tajima say
by virtue of the structure of a magnetic particle holding carrier having a micro-size nonmagnetic particulate carrier and a plurality of nano-size magnetic particles held on the carrier, magnetism can be imparted to the nonmagnetic carrier.
Furthermore, since a plurality of nano-size magnetic particles are massively deposited onto a micro-size nonmagnetic particulate carrier, magnetic force applied to a single particle can be increased.
At the same time, since the carrier is a micro-bead and the surface of the micro-bead is covered with nano beads, the surface area of such a structure comes to be increased, with the result that a surface area/volume ratio per particle can be reduced.
As shown in FIG. 1(a), the magnetic particle holding carrier 11 according to the first embodiment has a micro-size nonmagnetic particulate carrier 12 (for example, Streptavidin Coated Beads, 1 .mu.m YG manufactured by Polysciences, Ink.), which has a particle size of about 1 .mu.m and is formed of latex whose surface is coated with streptavidin 13 serving as the receptor; a nano-size super-magnetic single domain particle(s) 14, which serves as the magnetic particles and is coated with a substance having biotin 15 serving as a ligand and an amino group; and a fluorescent dye 16 (Cy3-NHS) introduced to the amino group.