The Size-Dependent Heating of Magnetic Iron. Oxide Nanoparticles

Transcription

1 The Size-Dependent Heating of Magnetic Iron Oxide Nanoparticles Sheng Tong 1, Christopher A. Quinto 2, Linlin Zhang 1, Priya Mohindra 2 and Gang Bao 1,2 * 1 Department of Bioengineering, Rice University, Houston, TX 77030, USA 2 Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA 30332, USA Supporting Information 1

2 Figure S1 Figure S1. XRD patterns of iron oxide nanocrystals. The nanocrystals dispersed in toluene were precipitated with ethanol and dried in a vacuum chamber overnight. Approximately 10~20 mg of each sample was used in the XRD analysis with an X-ray Diffractometer (Rigaku SmartLab). The patterns were collected within 15 and 90 in 2θ. 2

3 Figure S2 Figure S2. Inductive coils used in SAR measurements. The SAR measurements were carried out with two inductive coils, a small coil (7.5 turns, ID = 2.5 cm and height = 3 cm) and a large coil (5 turns, ID = 5 cm and height = 3 cm). A and C are the geometries of the two coils built in the COMSOL Multiphysics software respectively. The small cylinders in the coils represent the location of the samples. B and D are the magnetic fields simulated with the software. The currents in the two coils were 115 A and 130 A respectively. The rectangles in B and D represent the location and the volume of the samples. 3

4 Figure S3 Figure S3. Heating profiles of MIONs in water. Representative heating profiles are plotted for water and MIONs from 6 to 40 nm. The starting temperature was approximately 25 C. The temperature was recorded with a fiber optic temperature probe (Lumasense m3300) at a second interval. The concentrations were 1 mg Fe/mL for MIONs from 6 to 19 nm (solid lines) and 0.5 mg Fe/mL for MIONs from 25 to 40 nm (dashed lines) so that the temperature of the solution was within the effective measuring range of the temperature probe. The AMF was set at 20.7 ka/m and 325 khz. 4

5 Figure S4 Figure S4. Equilibrium magnetic properties of iron oxide nanocrystals. A. and B. are the normalized coercivity and remanence of the iron oxide nanocrystals extracted from the micro hysteresis measurements (Figures 3B and 3C). 5

6 Figure S5 Figure S5. Dependence of hysteresis of MIONs on field strength. A. Hysteresis of 40 nm iron oxide nanocrystals was scanned within the designated field strength. B. Loss per cycle calculated from the hysteresis loop shown in A. Note that in the micro hysteresis measurement, the 40 nm MIONs were scanned at quasi-static states determined by the DC scanning time of SQUID, not a theoretical equilibrium state. The curves shown in A were scanned at the frequencies determined by the instrument and varied with the range of the field. 6

7 Figure S6 Figure S6. ZFC and FC curves of iron oxide nanocrystals. ZFC and FC curves were scanned from 5 to 300 K with a magnetic field of 796 A/m (10 Oe). 7

8 Figure S7 Figure S7. AC susceptibility of iron oxide nanocrystals. A through H. Out-of-phase magnetic susceptibility of iron oxide nanocrystals scanned from 5 to 320 K and with an AC field of 1 Hz to 1000 Hz at 332 A/m (4Oe). 8

9 Figure S8 Figure S8. Anisotropy constants of iron oxide nanocrystals. A Linear plot of the inverse of maximum temperature of each frequency according to the Arrhenius law (6, 8 and 11 nm) and according to the Vogel-Fulcher law (15 nm). B. Anisotropy constants of iron oxide nanocrystals. For 6 to 15 nm nanocrystals, K A was calculated based on the linear fitting in A. K A of bulk magnetite was used for 19 to 40 nm nanocrystals. 9

10 Figure S9 Figure S9. Simulated dynamic hysteresis loops. Dynamic hysteresis loops were simulated for three representative MIONs, 11 nm, 19 nm and 33 nm, using a Matlab program based on a statistical physics model developed by Carrey et al. A, B and C plot the evolution of the hysteresis loops with the frequency of the magnetic field with the peak field strength equal to 20 ka/m. D plot the hysteresis for 33 nm MIONs but the peak field strength was increased to 30 ka/m. 10

11 Figure S10 Figure S10. MR images of mouse cross sections. MIONs (50 µg Fe) were dispersed in 10 µl of PBS and injected into the center of the tumors over 10 minutes with a syringe pump. The images were acquired with a 7T small animal MRI instrument (PharmaScan, Bruker) before and after injection of PBS, 6 nm, 19 nm and 40 nm MIONs respectively. 11

12 Figure S11 Figure S11. In vivo MFH set up. A tumor-bearing mouse anesthetized with isoflurane was placed in a customized polycarbonate cradle with a heating pad underneath to maintain body temperature. The mouse was placed in the coil with 5 cm inner diameter, while the tumor was centered inside the coil. 12

13 Figure S12 Figure S12. In vivo tumor heating profiles. AMF was exerted on the mice for 60 minutes. The temperature of the tumor was recorded with a fiber optic temperature probe bluntly inserted into the tumor. 13

14 Table S1. Comparison of SAR and α values of MIONs of sizes 6-40 nm under different applied magnetic field Size Field Strength Frequency SAR nm ka/m khz α Reference W/g Fe [26] [13] [22] [12] [22] 14