Effect of Magnetite Nanoparticle Agglomerates on the Destruction of Tumor Spheroids Using High Intensity Focused Ultrasound  Vincent H.B. Ho, Moira J. Smith, Nigel K.H. Slater  Ultrasound in Medicine and Biology  Volume 37, Issue 1, Pages 169-175 (January 2011) DOI: 10.1016/j.ultrasmedbio.2010.09.007 Copyright © 2011 World Federation for Ultrasound in Medicine & Biology Terms and Conditions

Fig. 1 Schematic of the HIFU experimental setup. The HeLa multicellular spheroid was resting at the bottom of the agar well and was insonated by the HIFU transducer. The HIFU-induced inertial cavitation was detected by the PCD. Ultrasound in Medicine and Biology 2011 37, 169-175DOI: (10.1016/j.ultrasmedbio.2010.09.007) Copyright © 2011 World Federation for Ultrasound in Medicine & Biology Terms and Conditions

Fig. 2 Graph of average ICD against time for the HIFU insonation of spheroids. The HIFU setup was operating at a frequency of 1.1 MHz, 1.67-kHz PRF and peak negative focal pressure of 7.2 MPa. Spheroids were insonated for 10 s and at the indicated duty cycles (DC). Five percent DC without () and with () magnetite nanoparticle agglomerates (MNP); and 50% DC without (♦) and with (●) MNP. Data represent the mean ± SE of four experiments performed in duplicate. Ultrasound in Medicine and Biology 2011 37, 169-175DOI: (10.1016/j.ultrasmedbio.2010.09.007) Copyright © 2011 World Federation for Ultrasound in Medicine & Biology Terms and Conditions

Fig. 3 Cell viability assay of HeLa multicellular spheroids using live/dead stain with calcein AM and ethidium homodimer-1. Viable cells appear as green, whereas nonviable cells appear as red. The spheroids were insonated with HIFU at a frequency of 1.1 MHz, 1.67-kHz PRF, peak negative focal pressure of 7.2 MPa for 10 s and at the indicated duty cycles (DC) in the presence or absence of magnetite nanoparticle agglomerates. (a) 0% DC without magnetite particles. (b) 0% DC with magnetite particles. (c) 5% DC without magnetite particles. (d) 5% DC with magnetite particles. (e) 50% DC without magnetite particles. (f) 50% DC with magnetite particles. Ultrasound in Medicine and Biology 2011 37, 169-175DOI: (10.1016/j.ultrasmedbio.2010.09.007) Copyright © 2011 World Federation for Ultrasound in Medicine & Biology Terms and Conditions

Fig. 4 (a) Quantitative analysis of spheroid destruction. The HeLa spheroids were insonated with HIFU in the absence (blank) or presence (grey) of magnetite nanoparticle agglomerates at different duty cycles with a frequency of 1.1 MHz, 1.67-kHz PRF and peak negative focal pressure of 7.2 MPa for 10 s. The areas, expressed in arbitrary units (a.u.), occupied by the spheroids, were measured and correlated to the structural integrity of spheroids. Data represent the mean ± SE of four experiments performed in duplicate. *p ≤ 0.001. (b) Phase contrast image of HeLa spheroid. Scale bar represents 250 μm. (c) Phase contrast image after HIFU insonation. Ultrasound in Medicine and Biology 2011 37, 169-175DOI: (10.1016/j.ultrasmedbio.2010.09.007) Copyright © 2011 World Federation for Ultrasound in Medicine & Biology Terms and Conditions