Superparamagnetic nanoparticle quantification using a giant magnetoresistive sensor and permanent magnets

Abstract

Magnetic nanoparticles are used in various biological applications such as magnetic resonance imaging (MRI), biological separation, drug delivery or as biomarker. In the case of biomarker, the magnetic particle and a measurand are combined via biological reactions and then detected by magnetic field sensors for a qualitative or quantitative measurement. In the present work, we introduce a commercially available giant magnetoresistive (GMR) sensor for the quantitative measurement of superparamagnetic nanoparticles, which were injected into a glass capillary tube. A pair of permanent magnets standing diagonally opposite to each other was utilized to provide vertical and horizontal magnetic fields for particle magnetization and sensor bias, respectively. In addition, the permanent magnets solved the uniformity problem of generated magnetic fields in previous biomarker detection systems. Using the proposed measurement setup, an output signal change of 0.407V was achieved for a 1μg change in the magnetic particle mass. The detection limit was 43.5ng.