Reconfigurable Magnetic Microswarm for Accelerating tPA-Mediated Thrombolysis under Ultrasound Imaging

We propose a strategy to accelerate tissue plasminogen activator (tPA)-mediated thrombolysis using a microswarm under ultrasound imaging. The microswarm is formed in blood using an oscillating magnetic field and navigated with switchable locomotion modes. The aspect ratio of the microswarm can be reversibly tuned by modulating the input field, enabling the capability to adapt to different clot regions. Simulations show that three-dimensional flow is induced around the microswarm, which enhances the mass transfer and shear stress near the clot-fluid interface. Guided by ultrasound imaging, the microswarm can be navigated towards clot regions and deformed to adapt to blood clots with different widths. Affected by the enhanced fluid convection and shear stress, experimental results show that the microswarm-assisted lysis rate enhances up to 3.13-fold compared to that using tPA drug only. Moreover, the comparison between microswarm-assisted thrombolysis in phosphate buffered saline (PBS) and blood environments validates our modeling and simulation results. Our method provides a strategy to increase the efficiency of tPA-mediated thrombolysis by applying an ultrasound-localized microrobotic swarm, indicating that swarming micro/nanorobots have the potential as effective tools towards imaging-guided therapy.