Study of spin dynamics in ferrite-based MNPs Dott. Martina Basini Supervised by: Alessandro...
Transcript of Study of spin dynamics in ferrite-based MNPs Dott. Martina Basini Supervised by: Alessandro...
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Study of spin dynamics
in ferrite-based MNPs
Dott. Martina BasiniSupervised by: Alessandro Lascialfari
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OUTLINE• Introduction to nanomagnetism
• SUPERPARAMAGNETIC nanoparticles (MNPs):– Biomedical appications– MNPs as theranostic agents
• MY RESEARCH :– Samples– Magnetic measurement– NMR Profiles – Results
• CONCLUSIONS and PERSPECTIVES
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SuperparamagnetismFerromagnetism
SOME CRITICAL DIAMETER:
INTRODUCTION TO NANOMAGNETISM
All the spin move coherently
COMPETITION between ANISOTROPY and THERMAL
ENERGY
Spins filipping in Nèel time
tN = t0(E) exp [DEa/Kb (T-T0)]
B = 0Ea = Barrier
d < Dc
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SUPERPARAMAGNETIC NANOPARTICLES
MAGNETIC CORE: MAGHEMITE (γ-Fe2O3) /
MAGNETITE (Fe3O4)
HOW ARE MNPs MADE?
HYDROPHOBIC COATING: OLEIC ACID
SOLVENTHEXANE / ACQUEUS MEDIA
POSSIBILITY OF FUNCTIONALIZATION
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Proteins
Virus
Cells
0.1 nm 1 nm 10 nm 100 nm 1 m 10 m 100 m
Gene (width) Bacteria
DNA
Human hair
pollen
Aspirin molecule
nanoparticles
SUPERPARAMAGNETIC NANOPARTICLESWHY ARE THEY APPEALING FOR BIOMEDICAL APPLICATIONS?
DIMENSION
MAGNETIC TRANSPORT
CAN BE BIOCOMPATIBLE
POSSIBLE
FUNCTIONALIS
ATION
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SUPERPARAMAGNETIC NANOPARTICLES
DIAGNOSTIC: CONTRAST AGENT (CA)
FOR MRI
With CAWithout CATHERANOSTIC AGENTS:
THERAPY: MAGNETIC
FLUIDHYPERTEMIA
TARGETING: DRUGS, ANTIBODY
THE IDEAL TASK: A single theranostic nano-object !!
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THE ROLE OF PHYSICIST
INVESTIGATION OF
FUNDAMENTAL magnetic properties and
relaxation rates’ mechanisms
CORRELATION WITH APPLICATIVE
properties
NMR RELAXATION
DISPERSION CURVES
MAGNETIC MEASUREMENTS
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Few words on NMR TECHNIQUENMR
RELAXATIONNUCLEI
(T2n)
ELECTRONS(T2e)
PHONONS
T1n
T1n T1e
LOCAL HYPERFINE INTERACTION
BETWEEN NUCLEI AND ELECTRON
NOW (Mz = 0): Start recording relaxation to equilibriumB1
90° PULSE
1/T1n ATJe(ωN)
1/T2n Je(0)Electronic
spectral densityJe(ω) = FT [G(r , t)]
1H relaxation:LOCAL PROBE
through the
EYES of HF INTERACTION!!
Probe: 1H (high natural abundance)Measure: relaxation time of 1H
• ALONE THEY WOULD RELAX IN YEARS• Interacting with MNP’s THEY RELAX IN t
< s
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dcore = 4 nm = 0.15
dcore = 8.5 nm = 0.07
dcore = 20 nm = 0.09
L = 8.5 nm
A
B
C
D
Solvent: HEXAN
Solvent: ACQUEOUS MEDIA
C_acq
D_acq
TEM
MY STUDY: SAMPLESGOALS:
APPLICATIVE: IDENTIFY NEW possible MRI Contrast AgentsFUNDAMENTAL: Study of SPIN DYNAMICS
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MY STUDY: AC and DC Magnetic measurement
-1400-1200-1000-800 -600 -400 -200 0 200 400 600 800 100012001400-10
0
10
M (
emu/
g)
H (Oe)
5K
-60000 -40000 -20000 0 20000 40000 60000-30
-20
-10
0
10
20
30
M (
em
u/g
)
H (Oe)
5K
0 20 40 60 80 100 120 140 160 180-0,5
0,0
0,5
1,0
1,5
2,0
2,5
CH
I (em
u/g)
T (K)
ZFC
FC
T < TB
TB
0 20 40 60 80 100 120 140 160 180
0,000
0,005
0,010
0,015
0,020
0,025
0,030
X (
em
u/g
)
T (K)
frequency
t = t0(E) exp [DEa/KB (T-T0)]
Max RESPONSE at TMAX TB
such thatω 1
BLOCKING-SPIN TEMPERATURE
ACD
C
HYSTERESIS Spins are bloked (H = 0 ; M 0)
DEa
t0
T0 MEASURE THE INTERACTIONS
10 -10 - 10-12 s
B = 0
B ≠ 0
M
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MY STUDY: NMR relaxation curves
1H relaxation times (T1 and T2) depend on the
capability to EXCHANGE ENERGY
with the sorrounding:
!! LOCAL PROBE !!
MNPs shorten the relaxation
time T2 of 1H of healty cells:
CONTRAST AGENTS
Key parameter for MNPs CA efficiency :
r2 ~ 1 / T2
Magnetic Resonant Imaging
MRI signal is:
s(t) = N(1H) e-TE/T2 (1-e-TR/T1)
Magnetic Resonant Imaging
MRI signal is:
s(t) = N(1H) e-TE/T2 (1-e-TR/T1)
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MY STUDY: NMR Results
0,01 0,1 1 10 100
0
5
10
15
20
25
30
35
40
45
50
55 M8 d = 4 nm M3 d = 8 nm M5 d = 20 nm
r2 (
s-1m
M-1)
freq (MHz)0,01 0,1 1 10 100
0
10
20
30
40
50
M3_HEX M3_EMU
r2 (
s-1m
Mo
l-1)
freq (MHz)
0,1 1 10 1000
10
20
30
M3 d = 8 nm SPHERIC M2 d = 8 nm CUBIC
r2
(s-1m
M-1)
freq (MHz)
HEXAN
Acqueus media INCREASE CA EFFICIENCY
SPHERICAL SHAPE
4 nm promising as negative CA!!
SIZE SOLVENT
SHAPE
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EXISTING MODELS….
...Work for r1…
...Don’t Work for r2..
0,01 0,1 1 10 100
5
10
15
r1
FREQ (MHz)
0,1 1 10 1002
4
6
8
10
12
14
16
18
20
22
24
26
28
30
32
r2
freq (MHz)
FIT LINES
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CONCLUSIONS and PERSPECTIVES SPHERICAL shape is better
d ~ 20 nm displays the BEST EFFICIENCY:
r2 = 50 s-1mM-1
d ~ 4 nm has r2 = 27 s-1mM-1, VERY HIGH with respect to
the SMALL SIZE…
WE NEED A THEORY FOR BOTH r1 and r2 !!!
…further work is required