Pulsed magnetic field-driven translational dynamics and estimated mechanical loading of magnetic particle clusters for thrombolysis

Limited molecular accessibility and insufficient local structural disruption can restrict fibrinolytic therapy. Here, a pulsed magnetic field (PMF)-driven magnetic particle cluster (MPC) strategy was developed for mechanically assisted thrombolysis using silicified carbonyl iron particles. A single PMF pulse rapidly assembled dispersed particles into compact spindle-like MPCs, while synchronized PMF output and coil reciprocation enabled their repeated translation within the thrombus region. An experimentally calibrated dynamic model reconstructed the axial magnetic driving force acting on 0.2 mg of MPCs, yielding estimated peak values of approximately 0.19–1.04 mN under PMFs with peak amplitudes of 0.25–1 T. In vitro thrombolysis experiments conducted using a 0.5 T PMF showed that the combined PMF + carbonyl iron powder (CIP)@SiO2 + tissue plasminogen activator (tPA) treatment achieved an apparent clot mass-loss rate of 0.104 mg min−1, exceeding the arithmetic sum of the rates produced by tPA alone and PMF-driven CIP@SiO2 alone. Subsequent dynamic fluorescence imaging showed concurrent thrombus structural disruption and penetration of a fluorescent tracer. After 60 min, the mean DiI fluorescence intensity decreased to approximately 51% of its initial value, whereas the dextran-positive area increased to approximately 55% of the initial thrombus area. These findings quantitatively characterize the translational response and available mechanical loading of pulsed magnetic field (PMF)-driven MPCs and demonstrate their potential to enhance tPA-mediated clot removal.