Multicore magnetic nanoparticles (MMNPs) doped with Cs and FITC for the determination of biomarker in serum using ICP-MS.

Multicore magnetic nanoparticles (MMNPs) doped with Cs and FITC (Cs/FITC-doped MMNPs) were synthesized for the extraction and determination of biomarkers using inductively coupled plasma-mass spectrometry (ICP-MS). For demonstration, the MMNPs were used for magnetic separation to extract CA19-9 in serum nonspecifically, and the doped Cs was used as an internal standard for the ratiometric measurement of the tagged particle. This ratiometric method compensated for the particle loss in a magnetic separation and suppressed the signal fluctuation which increased the calibration linearity significantly. The obtained detection limit was 0.02 units/mL of CA19-9, which is more than 300 times lower than that reported by the ICP-MS with element tagging and about 500-fold improved compared to ELISA.