Development of novel magnetic tweezers technologies: Applications to biomaterials characterization

Characterization of the mechanical properties of cells, as well as the tissues and extracellular matrices (ECM) in which they reside, requires microscale manipulation platforms that allow precise measurement of their local rheology. To achieve this, my laboratory has developed a suite of NdFeB-based magnetic tweezers devices optimized for biomaterials characterization. In this talk, I will present the design and construction of three new microscope-mounted magnetic tweezers devices that allow controlled forces to be applied locally to networks, cells, and tissues while their deformation is determined with nanometer accuracy: (1) high-force devices that enable the application of nN forces; (2) ring magnet devices that enable oscillatory microrheology without prestress; and (3) portable magnetic tweezers that enable visualization of the microscale deformation of soft materials under applied force through simultaneous fluorescence imaging. The utility of these devices will be demonstrated by measuring the mechanics of dense networks of microtubules, which are rigid cytoskeletal polymers. We find that crosslinker dynamics profoundly affect network elasticity and dynamics, and that it is possible to predict macroscale stiffness, strength, and stress propagation from the force-sensitive unbinding kinetics and compliance of single crosslinkers.