Detection of 8 nM Diameter Superparamagnetic Beads by Magnetically-Induced Manipulation of Micrometer-Sized Magnetic Beads: A Novel Protocol for Magnetically-Labeled Biosensing

摘要

Biosensing platforms based on functionalized superparamagnetic beads acting as "magnetic-labels" show tremendous potential for rapid and highly-sensitive point of care medical diagnosis. Recently, for greater quantification, there are increasing demands for the use of magnetic labels with diameters of 8-150 nm, which are comparable in size to actual biomolecules. However, detection of small numbers of sub-150nm sized magnetic beads by magnetoresistive device-based platforms is extremely challenging due to the intrinsic noise of these electronic devices. Here, we describe an easy and economical detection method of low areal -densities of 8-nm-diameter superparamagnetic "target beads" immobilized over millimeter-sized substrates by optically monitoring the magnetically induced "capture" of easily visible, micrometer sized superparamagnetic "columnar beads" by the targets in less than a few tens of seconds.