Liquid phase immunoassays utilizing magnetic markers and SQUID magnetometer.

Background: Immunoassays are one main detection system used in the field of clinical chemistry. Recent developments of a new detection method utilizing a magnetic marker and magnetic sensor have enabled rapid and sensitive immunoassay without the need for bound/free (BF) separation.

Methods: Newly-synthesized conjugated avidin was used as the magnetic marker for quantitative analysis of human interleukin-8 (hIL-8) and immunoglobulin E (hIgE) in several media.

Sonochemical coating of magnetite nanoparticles with silica.

Magnetite nanoparticles were coated with silica through the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) under ultrasonic irradiation. The ultrasonic irradiation was used to prevent the agglomeration of the magnetite particles and accelerate the hydrolysis and condensation of TEOS. TEM, DLS, XRF, VSM, TG and sedimentation test were used to characterize the silica-coated magnetite particles.

Sonochemical synthesis of monodispersed magnetite nanoparticles by using an ethanol-water mixed solvent.

The magnetite nanoparticles were synthesized in an ethanol-water solution under ultrasonic irradiation from a Fe(OH)(2) precipitate. XRD, TEM, TG, IR, VSM and UV/vis absorption spectrum were used to characterize the magnetite nanoparticles. It was found that the formation of magnetite was accelerated in ethanol-water solution in the presence of ultrasonic irradiation, whereas, it was limited in ethanol-water solution under mechanical stirring.

[Development of liquid phase immunoassay system using magnetic nanoparticles].

Biological immunoassay is a major detection system of biological materials from patient samples. Our group has been developing a highly sensitive immunoassay system using magnetic nanoparticles made from Fe3O4. Since unbound magnetic markers randomly move in solvent due to Brownian motion, there is no magnetic signal from unbound magnetic markers; therefore, the separation of bound from unbound markers (B/F separation) is not required.