Harmonic Responses And Cavitation Activity Of Encapsulated Microbubbles Coupled With Magnetic Nanoparticles

By coupling encapsulated microbubbles with magnetic nano-particles, a new type of dual-modality agents, which can be used to achieve the functions in both ultrasonic and magnetic resonance imaging, have attracted broad attentions in both acoustic and medical communities. Whereas, However, the dynamic responses of this kind of dual-modality agents generated in clinical applications have not been well understood. Here, a dual-modality agent was synthesized by integrating superparamagnetic iron oxide nanoparticles (SPIOs) into albumin-shelled bubbles (shorten for SPIO-albumin MBs). Then, both the stable and inertial cavitation (SC and IC) thresholds of this dual-modality agent were measured at varied SPIO concentrations and acoustic driving parameters (e.g., frequency, pressure amplitude, and pulse length). The results show that, at a fixed driving frequency, both the SC and IC thresholds of SPIO-albumin MB should be reduced by enhancing SPIO concentration and acoustic driving pulse length. The IC threshold of SPIO-albumin MBs also decreases with the increase in the acoustic driving frequency, while the minimum sub-and ultra-harmonic thresholds appear at twice and two thirds resonance frequency, respectively. It is also noticed that both the SC and IC thresholds of SonoVue bubbles are similar to those measured for dual-modality MBs with a SPIO concentration of 114.7 μg/ml. The current work would give us in-depth knowledge on the influence of the integrated magnetic nanoparticles on the dynamic motions (especially the SC and ICactivities) of dual-modality microbubbles, and suggest the shell composition of dual-modality agents should be appropriately designed to improve the practical performances of dual-modality MBs in clinics.