CHARACTERIZATION OF
SUPERPARAMAGNETIC IRON
OXIDE NANOPARTICLES
IN BIOLOGICAL ENVIRONMENTS
Melissa M. van de Loosdrecht
a,*, Sebastiaan Waanders
a, Hendrikus J.G. Krooshoop
a, and Bennie ten Haken
aa Magnetic Detection and Imaging group, Faculty of Science and Technology, University of Twente, Enschede, the Netherlands
Correspondence to: m.m.vandeloosdrecht@utwente.nl
Sentinel nodes
Tumor Tracer
BACKGROUND
PURPOSE
SPIONs are used as a tracer material in sentinel node biopsies. To locate them in vivo it is important to characterize them in vitro. In this way, the most effective particle can be chosen and the measurement protocol can be optimized. To do this, we developed the SuperParamagnetic Quantifier (SPaQ), a coaxial magnetometer,
which uses AC excitation fields between 1 and 10 kHz with an amplitude of approximately 1 mT.
When a patient is diagnosed with cancer, it is important to know if the tumor has spread through the body. Sentinel node biopsies are used to determine if the tumor has spread via the lymphatic system (Figure 1) [1]. Consequently, patient care
will be personalized.
METHODS
RESULTS
CONCLUSION
Acknowledgements
Financial support by the Netherlands Organization for Scientific Research (NWO), under the research program Magnetic Sensing for Laparoscopy (MagLap) with project number 14322, is gratefully
acknowledged.
FIGURE 1 Sentinel node biopsy. A tracer is injected inside or close to the
tumor and will accumulate in the first lymph nodes it reaches. A dedicated probe [2] is used to detect these sentinel nodes followed by surgical removal.
FIGURE 3 Schematic overview of SPaQ measurements. (a) A continuous AC magnetic field and changing DC offset are applied
to the nanoparticles. (b) The response of the particles is given by their magnetization curve. (c) The resulting magnetization of the particles over time. (d) The resulting signal is the changing magnetization. (e) The envelope of the signal is found by phase-sensitive detection; this is the derivative of the magnetization curve in two directions (which are almost identical). (f) Integration yields the magnetization curve. The blue and red colors indicate the direction in which the curve is measured.
FIGURE 4 SPaQ results, measured on ResovistTM and SHP-25 samples containing 750
µg iron in a total volume of 150 µl. b is a numerical integration of a.
The SPaQ is capable of measuring the dynamic magnetization curve of SPIONs at low field strengths and frequencies between 1 and 10 kHz. Therefore, it can give invaluable information about SPIONs, which will improve mentioned applications.
References
[1] A. E. Giuliano and A. Gangi, Breast J., vol. 21, no. 1, 2015.
[2] S. Waanders et al. Phys. Med. Biol., vol. 61, no. 22, pp. 8120–8134, Nov. 2016.
-20 0 20 0
H [mT]
0 0.02 0.04 0.06 0.08dM/dH [a.u.]
Resovist SHP25 -20 0 20 0H [mT]
-0.4 -0.2 0 0.2 0.4M [a.u.]
Resovist SHP25a
b
-40 -20 0 20 40Applied field [mT]
Magnetization [a.u.]
-40 -20 0 20 40Applied field [mT]
0 0.5 1Time [s]
0 0.5 1Time [s]
Magnetization [a.u.]
0 0.5 1Time [s]
Signal [a.u.]
-40 -20 0 20 40Applied field [mT]
Signal [a.u.]
-40 -20 0 20 40Applied field [mT]
Magnetization [a.u.]
a
b
c
d
e
f
OTHER APPLICATIONS
Besides sentinel node biopsy, there are many applications for the superparamagnetic quantifier:
• Study particles used for controlled drug delivery
• Study of the dynamic protein corona formation process • Optimizing the design process of SPIONs
FIGURE 2 Schematic representation of the SPaQ. An excitation coil
(blue) and a pair of gradiometer detection coils (green) surround a 23 mm diameter sample bore. Samples are placed in the topmost detection coil, which has a homogeneous field region of 2.5 cm along the vertical axis, in this region the field deviates no more than 5 %. An outer field coil (purple) is wound around the main excitation coils to correct for field imbalances and undesirable offsets.
