Low-Intensity Focused Ultrasound as a Strategy for Microclot lysis

Amyloid microclots have been implicated in thrombotic complications across various pathological conditions such as Long COVID symptoms, yet their resistance to enzymatic fibrinolysis causes a therapeutic challenge. In this study we examine the effects of three fibrinolytic enzymes rtPA, Lumbrokinase, and Nattokinase on plasma-derived amyloid microclots, in combination with ultrasound-induced microstreaming and microbubbles. A lab-on-chip platform was used to expose the clots to ultrasound at 150, 300, and 500 kHz. Quantitative analysis revealed that ultrasound alone significantly disrupted clot structures, particularly at 150 kHz, where mean clot diameter was reduced by over 60% and large-clot count (>30 µm) dropped by more than 80% compared to controls. The addition of fibrinolytic enzymes, however, did not produce statistically significant effects at 150 or 300 kHz which indicates that mechanical forces were the dominant contributors to clot disruption. At 500 kHz, where ultrasound alone was less effective, enzymatic treatment moderately enhanced the reduction in large-clot burden. These results show the potential of low-frequency ultrasound as a primary method of amyloid microclot breakdown, with enzyme co-treatment offering limited but measurable effect.