In this work, the time-dependent phase lag θ of biofunctionalized magnetic nanoparticles (BMNs) conjugated with biotargets is studied with a home-made alternating current (ac) susceptometor for liquid phase immunoassays. The sensing unit of the ac susceptometor composed of excitation, pick-up, and compensation coils are balanced to 0.03 ppm. The BMNs are anti-goat C-reactive protein coated onto dextran-coated magnetic nanoparticles composed of Fe 3O4, labeled as Fe3O4-antiCRP. The bio-targets are human CRP. As the human CRP is conjugated with reagents Fe 3O4-antiCRP, the magnetic clusters of Fe3O 4-antiCRP-CRP are formulated. Due to the clustering effect, the Brownian relaxation of BMNs will be depressed, which in turn enhances the effective relaxation time. By monitoring the dynamic phase lag, we demonstrate a sensitive platform of assaying human CRP. The detection platform is robust, easy to use and can be applied for assaying a wide variety of biotargets including viruses, proteins, tumor markers, chemicals, etc.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)