One of the most interesting uses of magnetic particles is for the in vivo capture, detection, concentration, or isolation of the target. This has been reported in various papers but only a few patents. One patent  describes a technique to isolate and remove an analyte from a body fluid. A molecule ligand, specific to the target, is immobilized on the surface of a magnetic particle. The particle is then introduced in vivo (in the body fluid) where it is tolerated long enough to enable the ligand to bind biologically to the target. Once the complex (ligand-target) is formed, it is retrieved from the body fluid by the application of a magnetic field.
The method is particularly fitted for detection of substance in gingival crevices for the diagnosis of periodontal disease. IgG against cachectin or interleu-kin-1 is chemically grafted to carboxyl groups. The magnetic particles are introduced in the cavity with a microdispenser. A magnetic field applied with a device anatomically compatible with the body cavity and adapted for the magnetic dispersion used then collects the magnetic particles.
Magnetic particles for in vivo applications are composed of a magnetic core bearing a hydrophilic-biocompatible biodegradable polymer shell layer or basic silica layer ; cells or tissues recognized by the particular bioaffinity adsorbent grafted on the magnetic particle are located, and therapeutic agents immobilized on the particles are delivered by magnetic direction to pathological sites.
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