Bead assembly magnetorotation as a signal transduction method for protein detection

This paper demonstrates a proof-of-principle for a new signal transduction method for protein detection called Bead Assembly Magnetorotation (BAM). BAM is based on using the target protein to mediate the formation of aptamer-coated 1 μm magnetic beads into a bead assembly, formed at the bottom of a 1 μL hanging droplet. The size, shape and fractal dimension of this bead assembly all depend on the protein concentration. The protein concentration can be measured in two ways: by magnetorotation, in which the rotational period of the assembly correlates with the protein concentration, or by fractal analysis. Additionally, a microscope-free magnetorotation detection method is introduced, based on a simple laser apparatus built from standard laboratory components. In this paper, we chose to focus on the protein thrombin, a popular choice for proof-of-principle work in this field.