Effect of magnetite nanoparticle agglomerates on the destruction of tumor spheroids using high intensity focused ultrasound.

Magnetite (Fe(3)O(4)) nanoparticle agglomerates have been shown to enhance the degree of inertial cavitation induced by high-intensity focused ultrasound (HIFU). To investigate the effect of these particles on the destruction of tumor spheroids using HIFU, HeLa spheroids were insonated in the presence and absence of magnetite nanoparticle agglomerates. The HIFU transducer was operated with a frequency of 1.1 MHz, pulse repetition frequency of 1.67 kHz, 5% and 50% duty cycles and peak negative focal pressure of 7.2 MPa for 10 s. The significant increase in the HIFU-induced inertial cavitation caused by the presence of magnetite particles at 50% duty cycle was sufficient to cause cell lysis and disintegrate the whole spheroid (p ≤ 0.001). This suggests that magnetite nanoparticle agglomerates can enhance the efficacy of HIFU in tumor ablation and other related therapies.