Optical Transmittance for Analysis of the Dynamics of Self-Assembled Rotating Chains of Superparamagnetic Micro- and Nano Beads in Solution

Optically monitoring biosensing procedures based on the dynamics of an aqueous solution containing functionalized superparamagnetic beads in the application of the external rotating magnetic field has been developed for a rapid, highly sensitive, and inexpensive bioassay. Typically, the dynamics of micrometer diameter beads is observed by conventional optical microscopes. For greater affinity to biomolecules, there is a demand which necessitates the use of nanometer sized superparamagnetic beads, comparable size to actual biomolecules. However, a limited amount of work for monitoring the dynamics of nanometer sized beads has been performed thus far due to the maximum resolution of microscopes. Here, we propose a novel protocol enabling us monitor the dynamics of nanometer-diameter beads via change in the optical transmittance.