Development of magnetic sensor technologies for point-of-care testing: Fundamentals, methodologies and applications

Abstract

Immunoassay based on the detection of magnetic nanoparticles (MNPs) has drawn great attention in the point-of-care testing (POCT) fields. Benefiting from the unique magnetic properties of MNPs, magnetic immunoassay possesses many advantages with more complete information of the labels and less interference from background. The developments of magnetic sensor technologies play vital roles in the quantification of MNPs and determine the directions and prospects of magnetic immunoassay. In this review, two kinds of magnetic sensor technologies including magnetoresistance (MR) sensor technology and magnetic induction (MI) sensor technology are discussed and their fundamentals as well as the applications of lateral flow immunoassay test (LFIT) strips or microfluidic biochips are summarized. MR sensor technology achieves detection with high accuracy and sensitivity by measuring the stray fields from MNPs under external excitation magnetic field. And magnetic induction sensor technology mainly detects the change of several magnetic physical quantities to realize the quantification of MNPs. Their different operating principles, measurement mechanisms and detection performances are given focus. In the meantime, their merits as well as limitations in practical applications are elaborated and compared. Future developments of magnetic immunoassay are expected to design integrated sensors with greater functions, which can accommodate smart detection and mobile detection supporting high performance.