Magnetic Nanoparticles in Hyperthermia Treatment
Transcript of Magnetic Nanoparticles in Hyperthermia Treatment
Wright State University Wright State University
CORE Scholar CORE Scholar
Special Session 5: Carbon and Oxide Based Nanostructured Materials (2012) Special Session 5
6-2012
Magnetic Nanoparticles in Hyperthermia Treatment Magnetic Nanoparticles in Hyperthermia Treatment
Gregory Kozlowski Wright State University - Main Campus, [email protected]
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MAGNETIC NANOPARTICLES IN HYPERTHERMIA TREATMENT
Gregory Kozlowski Wright State University, Physics Department, 3640 Col. Glenn Hwy., Dayton, OH 45435, USA
Magnetic hyperthermia represents a new non-surgical treatment of
cancerous tumors. In this treatment, some cancerous cells subjected to
elevated temperatures could be selectively destroyed leaving normal
cells unaffected. To achieve this, magnetic nanoparticles introduced to a
malignant tissue have to be subjected to an alternating (ac) magnetic
fields of sufficient intensities (kA/m) and frequencies (kHz - MHz). Due to
the ac magnetic field, the magnetic nanoparticles absorb energy and heat
the surrounding tissue, affecting only the infected cells. In my talk, I will
review the physics of heating mechanisms via magnetic nanoparticles
mostly determined by their sizes and magnetic properties. The
preparation techniques of mono- and bi-metallic magnetic nanoparticles
will be reviewed and their chemical, structural and physical properties will
be discussed in relation to hyperthermia treatment.
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Thtrapy
HYPERTHERMIA
Incorporation of Fe2O3 to mammal cell
Magnetic hyperthermia in cancer therapy
Overview
1. Introduction to magnetism
2. Single-domain nanoparticles
3. Magnetic heating (ferrites, Co, Fe, FePt)
4. Conclusions
5. Future work
1. Introduction to magnetism
Origin of Magnetism
Quantum mechanical phenomenon
Orbital motion and spin-1/2 rotational motion
of an electron are the source of magnetism
Dipole
• Maxwell's equations govern magnetism
Magnetic Variables
B, H and M
Magnetization
Magnetization is the measure of the strength of magnetism in a material.
It depends on density of magnetic dipole moments within material (N) and their magnitudes (mS).
ss NM m
Classification of Materials
H
M
Susceptibility (material’s ability to be magnetized due to presence of externally applied magnetic field)
Ferromagnetism : strong and attractive magnetic interaction toward a
magnetic pole.
χ >> 0. Highly dependent on temperature Paramagnetism : interaction is weakly attractive toward a magnetic pole.
χ > 0. Highly dependent on temperature Diamagnetism : interaction is weakly repulsive with respect to a magnetic
pole.
χ < 0. Independent of temperature
Hysteresis Loop (M-H graph)
Shows history nature of magnetization
Applicable for ferromagnetic materials
Magnetization is different with increasing fields as
compared to decreasing fields
M Saturaion
Retertivity
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Saturation
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Magnetic domains exist in order to reduce the
overall energy of the system.
Hysteresis Loop
• Saturation magnetization Ms occurs when all
the domains are perfectly aligned with the
field.
• Remnant magnetization Mr remains when
applied field is removed.
• Coercive field Hc should be applied in
opposite direction to reduce M to zero.
2. Magnetism of single-domain nanoparticles
Size restriction where material cannot
gain favourable energy configuration by
breaking into domains.
Particles smaller than the wall thickness
are single-domain nanoparticles.
Ferromagnetic materials tend to form magnetic domains as domain structure minimizes energy due to stray fields
Schematic of how a material becomes magnetised as the field increases.
Coercivity
• Larger for single-domain nanoparticles
• E.g., Fe (~15nm): 600 - 973 Oe
Fe (>>15nm): 2 Oe
• Process of magnetic reversal:
Domain wall motion
Magnetization rotation by rotation of atomic
spins
Size effect on ferromagnetic/superparamagnetic nanoparticles.
Ferromagnetic nanoparticles undergo a change from multi-domain to single
domain nanoparticles and further reduction in the size modifies their behavior
from ferromagnetic to superparamagnetic. The red curve corresponds to
superparamagnetic state while the blue/green curves are ferromagnetic states.
Superparamagnetism Defined by flips in the overall spin state of the system
due to temperature.
Neel relaxation time (H = 0): kT
KV
oe
• Ordering of the system is not lost, only the orientation of the
ordering (all spins may flip from up to down but retain their
average values)
• Occurs below Tc: Blocking temperature (Tb) by FC-ZFC
• Paramagnetic < χ < Ferromagnetic
Superparamagnetic
3. Magnetic Heating
MAGNETIC NANOPARTICLES
Absorption properties in radio-frequency and microwave range
Nanocrystalline Co2xNi0.5-xZn0.5-xFe2O4 (x = 0, 0.1, 0.2, 0.5) thin films (ferrites) have
been synthesized with various grain sizes by a sol–gel method on polycrystalline
silicon substrates. The morphology, magnetic and microwave absorption properties of
the films calcined in 1073 K were studied with XRD, SEM and vibrating sample
magnetometer. All films were uniform without microcracks. The Co content in Co-Ni-Zn
films resulted in the grain size ranging from 33.5 to 48.7 nm.
The saturation and remnant magnetization increased with increasing the grain size,
while the coercivity demonstrated a drop due to multi-domain behavior of crystallites
for a given value of x. The complex permittivity of the Co-Ni-Zn ferrite films was
measured in the frequency range of 2–15 GHz. The maximum absorption band shifted
from 13 to 11 GHz as the cobalt content was increased from x = 0.1 to 0.2.
RF HEATING SYSTEM
Fiber Optics T. Probe
Coil
Current
Frequency generator
Water Cooling
Vacuum
Supply
HEATING PROCESSES
i. Hysteretic losses
ii. Neel and Brown relaxation M
losses
iii. Frictional losses in viscous
suspensions
Power loss Ferromagnetic
Pf = - f
Superparamagnetic(at lower frequencies)
Ps = m0p0H02f2N/B
Frictional losses
Pfric = 2pf
Specific Power Loss
Since nanoparticles are going to be irradiated by a magnetic field, they are
going to liberate heat to their surroundings.
The term specific power loss (SPL), or more commonly known as
specific absorption rate (SAR) in the medical field, represents the standard
measure of the heating performance of magnetic nanoparticles and is the
power per unit weight of nanoparticles.
DQ = mc DT and P = DQ/Dt
SPL = c (DT/Dt) = P/m
Specific power loss
• Choice of frequency: 100kHz - 400kHz
• Determination of SPL (W/g) or SPL1 (W/g2)
1. Hysteretic loop
2. Calorimetric method
i. Dry powder
ii. Suspension in gel
The diameter of the coil is 3
cm and the length is 4 cm. (a) The magnetic field relative to the position
inside the coil, (b) the legend for the intensity of the field. (a)
Our custom coil consists of insulated
copper sheets wrapped around each other
20 times in the form of a spiral.
(b)
Ambrell EASYHEAT induction heater - The power supply with a coil
mounted on the work head in a zoomed image of the LCD panel and
touchpad. It displays the current flowing through the coil and the frequency
of oscillation.
Inner Diameter: 27 mm Tube Diameter: 6.35 mm
Length: 80 mm
Spacing between the tubes: 6 mm
The magnetic field relative to the position inside the coil with the corresponding legend.
Ni0.5Zn0.5Fe2O4
Ni0.5Zn0.5Fe2O4
RESULTS OF RF HEATING MEASUREMENTS
0
10
20
30
40
50
60
70
SP
L(W
/g)
0 100 200 300 400 500 600 700
Hc (Oe) at 75.6A
Co NANOPARTICLES with several COATING OPTIONS to avoid oxidation
Nanoparticle Diameter
[nm]
Coating
thickness
[nm]
Coating
Co31 6.5 ~0.3 - 0.6
bis(2-
ethylhexyl)
sulfosuccinate
Co51 7.3 ~1 Oleic acid+
Dibutylamine
Co41 8.2 <2
Oleic acid+
Triphenyl
phosphine
Co1 8.7 ~1 Oleic acid
Co21 20.0 ~1.6 PVP
CRITICAL DIAMETER for SINGLE DOMAIN = 15 nm
CRITICAL DIAMETER for SUPERPARAMAGNETISM = 6 nm
Specific Power Loss for Co NANOPARTICLES
Nanoparticle Diameter
[nm]
Coercivity
[Oe]
SPL1(15 A, 348 kHz)
[W/g2] Type
Co31 6.5 0 0.351 Superparamagnet
Co51 7.3 0 0.378 Superparamagnet
Co41 8.2 0 1.316 Superparamagnet
Co1 8.7 ~0 0.176 Single-domain
Ferromagnet
Co21 20.0 601 0.147 Multi-domain
Ferromagnet
CRITICAL DIAMETER for SINGLE DOMAIN = 15 nm
CRITICAL DIAMETER for SUPERPARAMAGNETISM = 6 nm
4. Conclusions
A. Ferromagnetic (ferrites) nanoparticles with
• High saturation magnetization
• Very low coercivity
have the highest specific power loss (SPL).
B. Maximum heating in superparamagnetic
regime is observed for Co nanoparticles
with diameter of 8.2 nm.
5. Future work RF heating characteristics and magnetic properties of
solid colloidal FePt nanoparticles
Typical RF heating curve at 15 A and 200 kHz - temperature
of superparamagnetic nanoparticle (BKFePt3) versus time
Sample Mean diameter (nm)
BKFePt2 8.781
BKFePt3 5.540
BKFePt5 4.407
BKFePt6 2.785
BKFePt7 7.352
BKFePt8 8.295
BKFePt9 3.838
COLLABORATORS
Cambridge University – P. Abdulkin, B. Knappett and A. Wheatley
Queens University, Belfast – T. Houlding and V. Degirmenci
Wright State University, Dayton – A. Sheets, Z. Jagoo and A. Lukawska
AFRL – Z. Turgut, H. Kosai and T. Bixel
FUNDING AGENCIES
AFOSR, EOARD, BRITISH COUNCIL, DAGSI, AFRL, NSF
Thank you