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Structural properties of magnetic nanoparticles determine their heating behavior - an estimation of the in vivo heating potential.

Ludwig R, Stapf M, Dutz S, Müller R, Teichgräber U, Hilger I - Nanoscale Res Lett (2014)

Bottom Line: Multicore MNP manufactured via different synthesis routes (fluidMAG-D, fluidMAG/12-D) showed different SAR although they exhibited comparable core and hydrodynamic sizes.Similar processes are supposed to take place in vivo, particularly when MNP are immobilized in cells and tissues.This aspect should be adequately considered when determining the SAR of MNP for magnetic hyperthermia.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Experimental Radiology, Division of Diagnostic and Interventional Radiology, University Hospital Jena - Friedrich Schiller University Jena, Forschungszentrum Lobeda, Erlanger Allee 101, D-07747 Jena, Germany.

ABSTRACT
Magnetically induced heating of magnetic nanoparticles (MNP) in an alternating magnetic field (AMF) is a promising minimally invasive tool for localized tumor treatment by sensitizing or killing tumor cells with the help of thermal stress. Therefore, the selection of MNP exhibiting a sufficient heating capacity (specific absorption rate, SAR) to achieve satisfactory temperatures in vivo is necessary. Up to now, the SAR of MNP is mainly determined using ferrofluidic suspensions and may distinctly differ from the SAR in vivo due to immobilization of MNP in tissues and cells. The aim of our investigations was to study the correlation between the SAR and the degree of MNP immobilization in dependence of their physicochemical features. In this study, the included MNP exhibited varying physicochemical properties and were either made up of single cores or multicores. Whereas the single core MNP exhibited a core size of approximately 15 nm, the multicore MNP consisted of multiple smaller single cores (5 to 15 nm) with 65 to 175 nm diameter in total. Furthermore, different MNP coatings, including dimercaptosuccinic acid (DMSA), polyacrylic acid (PAA), polyethylenglycol (PEG), and starch, wereinvestigated. SAR values were determined after the suspension of MNP in water. MNP immobilization in tissues was simulated with 1% agarose gels and 10% polyvinyl alcohol (PVA) hydrogels. The highest SAR values were observed in ferrofluidic suspensions, whereas a strong reduction of the SAR after the immobilization of MNP with PVA was found. Generally, PVA embedment led to a higher immobilization of MNP compared to immobilization in agarose gels. The investigated single core MNP exhibited higher SAR values than the multicore MNP of the same core size within the used magnetic field parameters. Multicore MNP manufactured via different synthesis routes (fluidMAG-D, fluidMAG/12-D) showed different SAR although they exhibited comparable core and hydrodynamic sizes. Additionally, no correlation between ζ-potential and SAR values after immobilization was observed. Our data show that immobilization of MNP, independent of their physicochemical properties, can distinctly affect their SAR. Similar processes are supposed to take place in vivo, particularly when MNP are immobilized in cells and tissues. This aspect should be adequately considered when determining the SAR of MNP for magnetic hyperthermia.

No MeSH data available.


Related in: MedlinePlus

TEM micrographs revealing different core characteristics of investigated magnetite MNP. TEM micrographs of OD15 (A), MF66 (B), fluidMAG-D (100 nm) (C), fluidMAG/12-D (100 nm) (D), fluidMAG-D (150 nm) (E), nanomag-D (130 nm) (F), and fluidMAG-D (200 nm) (G) MNP. Magnification = ×75000 (B, D, F). Magnification = ×160000 (A, C, E, G).
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Figure 2: TEM micrographs revealing different core characteristics of investigated magnetite MNP. TEM micrographs of OD15 (A), MF66 (B), fluidMAG-D (100 nm) (C), fluidMAG/12-D (100 nm) (D), fluidMAG-D (150 nm) (E), nanomag-D (130 nm) (F), and fluidMAG-D (200 nm) (G) MNP. Magnification = ×75000 (B, D, F). Magnification = ×160000 (A, C, E, G).

Mentions: HRTEM micrographs of single core OD15 and MF66 revealed a spherical structure of iron oxide cores with a narrow size distribution. The average core size was measured to be 15 ± 2 nm for OD15 and 12 ± 3 nm for MF66 MNP (Figure 2A, B). In contrast, fluidMAG-D, fluidMAG/12-D, and nanomag-D multicore MNP consisted of multiple irregularly clustered single cores different in size and shape (Figure 2C, D, E, F, G). Generally, agglomeration of single core MNP and the destruction of the spherical shape of multicore MNP clusters due to the sample preparation for HRTEM micrographs were observed.


Structural properties of magnetic nanoparticles determine their heating behavior - an estimation of the in vivo heating potential.

Ludwig R, Stapf M, Dutz S, Müller R, Teichgräber U, Hilger I - Nanoscale Res Lett (2014)

TEM micrographs revealing different core characteristics of investigated magnetite MNP. TEM micrographs of OD15 (A), MF66 (B), fluidMAG-D (100 nm) (C), fluidMAG/12-D (100 nm) (D), fluidMAG-D (150 nm) (E), nanomag-D (130 nm) (F), and fluidMAG-D (200 nm) (G) MNP. Magnification = ×75000 (B, D, F). Magnification = ×160000 (A, C, E, G).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230907&req=5

Figure 2: TEM micrographs revealing different core characteristics of investigated magnetite MNP. TEM micrographs of OD15 (A), MF66 (B), fluidMAG-D (100 nm) (C), fluidMAG/12-D (100 nm) (D), fluidMAG-D (150 nm) (E), nanomag-D (130 nm) (F), and fluidMAG-D (200 nm) (G) MNP. Magnification = ×75000 (B, D, F). Magnification = ×160000 (A, C, E, G).
Mentions: HRTEM micrographs of single core OD15 and MF66 revealed a spherical structure of iron oxide cores with a narrow size distribution. The average core size was measured to be 15 ± 2 nm for OD15 and 12 ± 3 nm for MF66 MNP (Figure 2A, B). In contrast, fluidMAG-D, fluidMAG/12-D, and nanomag-D multicore MNP consisted of multiple irregularly clustered single cores different in size and shape (Figure 2C, D, E, F, G). Generally, agglomeration of single core MNP and the destruction of the spherical shape of multicore MNP clusters due to the sample preparation for HRTEM micrographs were observed.

Bottom Line: Multicore MNP manufactured via different synthesis routes (fluidMAG-D, fluidMAG/12-D) showed different SAR although they exhibited comparable core and hydrodynamic sizes.Similar processes are supposed to take place in vivo, particularly when MNP are immobilized in cells and tissues.This aspect should be adequately considered when determining the SAR of MNP for magnetic hyperthermia.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Experimental Radiology, Division of Diagnostic and Interventional Radiology, University Hospital Jena - Friedrich Schiller University Jena, Forschungszentrum Lobeda, Erlanger Allee 101, D-07747 Jena, Germany.

ABSTRACT
Magnetically induced heating of magnetic nanoparticles (MNP) in an alternating magnetic field (AMF) is a promising minimally invasive tool for localized tumor treatment by sensitizing or killing tumor cells with the help of thermal stress. Therefore, the selection of MNP exhibiting a sufficient heating capacity (specific absorption rate, SAR) to achieve satisfactory temperatures in vivo is necessary. Up to now, the SAR of MNP is mainly determined using ferrofluidic suspensions and may distinctly differ from the SAR in vivo due to immobilization of MNP in tissues and cells. The aim of our investigations was to study the correlation between the SAR and the degree of MNP immobilization in dependence of their physicochemical features. In this study, the included MNP exhibited varying physicochemical properties and were either made up of single cores or multicores. Whereas the single core MNP exhibited a core size of approximately 15 nm, the multicore MNP consisted of multiple smaller single cores (5 to 15 nm) with 65 to 175 nm diameter in total. Furthermore, different MNP coatings, including dimercaptosuccinic acid (DMSA), polyacrylic acid (PAA), polyethylenglycol (PEG), and starch, wereinvestigated. SAR values were determined after the suspension of MNP in water. MNP immobilization in tissues was simulated with 1% agarose gels and 10% polyvinyl alcohol (PVA) hydrogels. The highest SAR values were observed in ferrofluidic suspensions, whereas a strong reduction of the SAR after the immobilization of MNP with PVA was found. Generally, PVA embedment led to a higher immobilization of MNP compared to immobilization in agarose gels. The investigated single core MNP exhibited higher SAR values than the multicore MNP of the same core size within the used magnetic field parameters. Multicore MNP manufactured via different synthesis routes (fluidMAG-D, fluidMAG/12-D) showed different SAR although they exhibited comparable core and hydrodynamic sizes. Additionally, no correlation between ζ-potential and SAR values after immobilization was observed. Our data show that immobilization of MNP, independent of their physicochemical properties, can distinctly affect their SAR. Similar processes are supposed to take place in vivo, particularly when MNP are immobilized in cells and tissues. This aspect should be adequately considered when determining the SAR of MNP for magnetic hyperthermia.

No MeSH data available.


Related in: MedlinePlus