Asynchronous Magnetic Bead Rotation (AMBR) Viscometer for Label-Free DNA Detection in Digestion and Quantitative PCR

Sensitive and low-cost DNA detection methods have a wide range of applications from clinical diagnostics and drug development to the food industry and forensic sciences. Here we report a cost-effective label-free DNA detection technology using asynchronous magnetic bead rotation (AMBR) viscometer. In our work, we have demonstrated theoretically and experimentally that the rotation period of the asynchronous motion is linearly proportional to the viscosity of a DNA solution surrounding a magnetic bead in a low Reynolds number regime. The viscosity of a DNA solution at a fixed temperature, which depends on the molecular weight of the DNA strands and the concentration of the solution, can be used to calculate DNA concentration. By measuring the rotation periods of magnetic beads, we have measured the viscosity of DNA aqueous solutions, digestion reaction solutions and quantitative PCR (qPCR) solutions with different initial template concentrations. The results prove the feasibility of viscosity-based DNA detection using AMBR method.