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Polymer/Iron Oxide Nanoparticle Composites--A Straight Forward and Scalable Synthesis Approach.

Sommertune J, Sugunan A, Ahniyaz A, Bejhed RS, Sarwe A, Johansson C, Balceris C, Ludwig F, Posth O, Fornara A - Int J Mol Sci (2015)

Bottom Line: Multi-core particles were obtained within the Z-average size range of 130 to 340 nm.With the aim to combine the fast room temperature magnetic relaxation of small individual cores with high magnetization of the ensemble of SPIONs, we used small (<10 nm) core nanoparticles.The performed synthesis is highly flexible with respect to the choice of polymer and SPION loading and gives rise to multi-core particles with interesting magnetic properties and magnetic resonance imaging (MRI) contrast efficacy.

View Article: PubMed Central - PubMed

Affiliation: SP, Technical Research Institute of Sweden, Box 5607, SE-114 86 Stockholm, Sweden. jens.sommertune@sp.se.

ABSTRACT
Magnetic nanoparticle systems can be divided into single-core nanoparticles (with only one magnetic core per particle) and magnetic multi-core nanoparticles (with several magnetic cores per particle). Here, we report multi-core nanoparticle synthesis based on a controlled precipitation process within a well-defined oil in water emulsion to trap the superparamagnetic iron oxide nanoparticles (SPION) in a range of polymer matrices of choice, such as poly(styrene), poly(lactid acid), poly(methyl methacrylate), and poly(caprolactone). Multi-core particles were obtained within the Z-average size range of 130 to 340 nm. With the aim to combine the fast room temperature magnetic relaxation of small individual cores with high magnetization of the ensemble of SPIONs, we used small (<10 nm) core nanoparticles. The performed synthesis is highly flexible with respect to the choice of polymer and SPION loading and gives rise to multi-core particles with interesting magnetic properties and magnetic resonance imaging (MRI) contrast efficacy.

No MeSH data available.


Related in: MedlinePlus

Normalized signal of the relaxation cycle of a MRX (magnetorelaxometry) measurement recorded on sample A in comparison to FeraSpin™-R with the fluxgate setup. No difference between suspended and immobilized particles is discernable for Sample A in contrast to FeraSpin™-R.
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ijms-16-19752-f010: Normalized signal of the relaxation cycle of a MRX (magnetorelaxometry) measurement recorded on sample A in comparison to FeraSpin™-R with the fluxgate setup. No difference between suspended and immobilized particles is discernable for Sample A in contrast to FeraSpin™-R.

Mentions: We also performed magnetorelaxometry (MRX) to determine the magnetic relaxation mechanism to confirm superparamagnetic behavior in Samples A and B, compared to FeraSpin™-R. In MRX measurement, a magnetic nanoparticle sample is polarized for 1–2 s in a static magnetic field of a few mT [25,26]. After abruptly switching off the field, the particles relax via Néel or Brownian rotation and the decay of the magnetic moment is recorded. Thus, MRX provides information on the relaxation times. For immobilized samples, the magnetic nanoparticles relax via the internal Néel mechanism, whereas for magnetic nanoparticle suspensions both Brownian and Néel relaxation can take place whereby the faster of the two dominates. The MRX measurements on samples A, B and core only, show no analyzable decay of magnetic moment for the fluid samples or the immobilized particles (as shown for Sample A in Figure 10). This indicates that the effective time constant is so short that the magnetic moments can follow the magnetic field changes almost instantaneously. This is in contrast to the behavior of FeraSpin™-R which exhibits distinct relaxation behavior in spite of similar crystallite sizes of 5–7 nm. For FeraSpin™-R, a clear relaxation signal is observed for both the suspended and the freeze-dried reference sample. The slower relaxation for the freeze-dried sample in which only Néel relaxation can take place indicates that the dynamics of at least part of the nanoparticles in FeraSpin™-R suspensions is dominated by Brownian rotation. A possible explanation is that the magnetic cores of samples A and B do not undergo the dipolar coupling that is responsible for the observed relaxation signal in FeraSpin™-R. Reduced dipolar coupling can originate either in larger inter-crystallite distances or in smaller magnetic moments per crystallites. Further investigations will confirm which of these factors contribute to the reduced dipolar coupling in our samples compared to FeraSpin™-R.


Polymer/Iron Oxide Nanoparticle Composites--A Straight Forward and Scalable Synthesis Approach.

Sommertune J, Sugunan A, Ahniyaz A, Bejhed RS, Sarwe A, Johansson C, Balceris C, Ludwig F, Posth O, Fornara A - Int J Mol Sci (2015)

Normalized signal of the relaxation cycle of a MRX (magnetorelaxometry) measurement recorded on sample A in comparison to FeraSpin™-R with the fluxgate setup. No difference between suspended and immobilized particles is discernable for Sample A in contrast to FeraSpin™-R.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4581323&req=5

ijms-16-19752-f010: Normalized signal of the relaxation cycle of a MRX (magnetorelaxometry) measurement recorded on sample A in comparison to FeraSpin™-R with the fluxgate setup. No difference between suspended and immobilized particles is discernable for Sample A in contrast to FeraSpin™-R.
Mentions: We also performed magnetorelaxometry (MRX) to determine the magnetic relaxation mechanism to confirm superparamagnetic behavior in Samples A and B, compared to FeraSpin™-R. In MRX measurement, a magnetic nanoparticle sample is polarized for 1–2 s in a static magnetic field of a few mT [25,26]. After abruptly switching off the field, the particles relax via Néel or Brownian rotation and the decay of the magnetic moment is recorded. Thus, MRX provides information on the relaxation times. For immobilized samples, the magnetic nanoparticles relax via the internal Néel mechanism, whereas for magnetic nanoparticle suspensions both Brownian and Néel relaxation can take place whereby the faster of the two dominates. The MRX measurements on samples A, B and core only, show no analyzable decay of magnetic moment for the fluid samples or the immobilized particles (as shown for Sample A in Figure 10). This indicates that the effective time constant is so short that the magnetic moments can follow the magnetic field changes almost instantaneously. This is in contrast to the behavior of FeraSpin™-R which exhibits distinct relaxation behavior in spite of similar crystallite sizes of 5–7 nm. For FeraSpin™-R, a clear relaxation signal is observed for both the suspended and the freeze-dried reference sample. The slower relaxation for the freeze-dried sample in which only Néel relaxation can take place indicates that the dynamics of at least part of the nanoparticles in FeraSpin™-R suspensions is dominated by Brownian rotation. A possible explanation is that the magnetic cores of samples A and B do not undergo the dipolar coupling that is responsible for the observed relaxation signal in FeraSpin™-R. Reduced dipolar coupling can originate either in larger inter-crystallite distances or in smaller magnetic moments per crystallites. Further investigations will confirm which of these factors contribute to the reduced dipolar coupling in our samples compared to FeraSpin™-R.

Bottom Line: Multi-core particles were obtained within the Z-average size range of 130 to 340 nm.With the aim to combine the fast room temperature magnetic relaxation of small individual cores with high magnetization of the ensemble of SPIONs, we used small (<10 nm) core nanoparticles.The performed synthesis is highly flexible with respect to the choice of polymer and SPION loading and gives rise to multi-core particles with interesting magnetic properties and magnetic resonance imaging (MRI) contrast efficacy.

View Article: PubMed Central - PubMed

Affiliation: SP, Technical Research Institute of Sweden, Box 5607, SE-114 86 Stockholm, Sweden. jens.sommertune@sp.se.

ABSTRACT
Magnetic nanoparticle systems can be divided into single-core nanoparticles (with only one magnetic core per particle) and magnetic multi-core nanoparticles (with several magnetic cores per particle). Here, we report multi-core nanoparticle synthesis based on a controlled precipitation process within a well-defined oil in water emulsion to trap the superparamagnetic iron oxide nanoparticles (SPION) in a range of polymer matrices of choice, such as poly(styrene), poly(lactid acid), poly(methyl methacrylate), and poly(caprolactone). Multi-core particles were obtained within the Z-average size range of 130 to 340 nm. With the aim to combine the fast room temperature magnetic relaxation of small individual cores with high magnetization of the ensemble of SPIONs, we used small (<10 nm) core nanoparticles. The performed synthesis is highly flexible with respect to the choice of polymer and SPION loading and gives rise to multi-core particles with interesting magnetic properties and magnetic resonance imaging (MRI) contrast efficacy.

No MeSH data available.


Related in: MedlinePlus