Patent ID: 7560289

Claim:
A method of quantitatively measuring an amount of biomolecules in a sample comprising: providing a solution having magnetic nanoparticles; coating bioprobe molecules to surfaces of the magnetic nanoparticles in the solution; measuring a first alternating current (ac) magnetic susceptibility of the solution at a mixture frequency (mf 1 +nf 2 ), wherein m or n is independently an integer larger than zero, f 1 is integral times of f 2 ; adding a sample containing the biomolecules to be detected to the solution, so that the biomolecules in the sample conjugate with the bioprobe molecules coated on the nanoparticles; measuring a second ac magnetic susceptibility of the solution at the mixture frequency (mf 1 +nf 2 ) after adding the sample, so as to obtain an ac magnetic susceptibility reduction at the mixture frequency (mf 1 +nf 2 ) between the first and the second magnetic susceptibility to determine the amount of the biomolecules.