Patent ID: 8447379

Claim:
A method of determining the presence, location, quantity, or a combination thereof, of one or more biological substances, comprising: (a) exposing a sample to a plurality of targeted nanoparticles, where each targeted nanoparticle comprises a paramagnetic nanoparticle conjugated with one or more targeting agents that preferentially bind with at least one of the biological substances, under conditions that facilitate binding of at least one of the targeting agents to at least one of the one or more biological substances; (b) subjecting the sample to a magnetic field of sufficient strength to induce magnetization of the nanoparticles; (c) measuring a magnetic field of the sample after decreasing the magnetic field applied in step b below a threshold; (d) fitting a decay curve of the magnetic field as measured over a period of time to a log/exponential function to determine the magnetic field of the sample at the time the magnetic field was decreased in step c to determine the presence, location, quantity, or a combination thereof, of the one or more biological substances from the magnetic field measured in step c.