Limits...
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

Immobilization in PVA decreases the SAR of singlecore MNP OD15 and MF66. Immobilization in PVA decreases the SAR of single-core MNP OD15 and MF66 by a factor of two compared to the respective water suspensions. SAR values of single core MNP in water suspension and immobilized in 1% agarose and 10% PVA. Additionally, hydrodynamic diameters (Øhydr.) for each MNP type are shown. Values in brackets indicate core size determined by TEM micrographs. Error bars indicate standard deviation of three independent measurements. OD15 coated with dimercaptosuccinic acid (DMSA) (A); OD15 coated with polyethylenglycol (PEG) exhibiting different molecular weights (B); MF66 coated with DMSA, polyacrylic acid (PAA), and PEG10000 (C); and MF66 coated with PEG10000-NH2(D).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4230907&req=5

Figure 3: Immobilization in PVA decreases the SAR of singlecore MNP OD15 and MF66. Immobilization in PVA decreases the SAR of single-core MNP OD15 and MF66 by a factor of two compared to the respective water suspensions. SAR values of single core MNP in water suspension and immobilized in 1% agarose and 10% PVA. Additionally, hydrodynamic diameters (Øhydr.) for each MNP type are shown. Values in brackets indicate core size determined by TEM micrographs. Error bars indicate standard deviation of three independent measurements. OD15 coated with dimercaptosuccinic acid (DMSA) (A); OD15 coated with polyethylenglycol (PEG) exhibiting different molecular weights (B); MF66 coated with DMSA, polyacrylic acid (PAA), and PEG10000 (C); and MF66 coated with PEG10000-NH2(D).

Mentions: In general, the immobilization of MNP in PVA resulted in decreased SAR values compared to MNP suspended in water, independently of their core structure, core size, and hydrodynamic diameter. Moreover, SAR values were reduced approximately by a factor of two after PVA immobilization in comparison to MNP suspended in water. The embedment of MNP in 1% agarose led to higher SAR values than the immobilization in 10% PVA, confirming a weaker immobilization of MNP in agarose than in PVA.The single core OD15 MNP, which were coated with DMSA and suspended in water, exhibited SAR values of 658 W/g Fe. Immobilization in 1% agarose decreased SAR to approximately 84% (550 W/g Fe). Lowest SAR values (382 W/g Fe) were observed after immobilization in PVA (Figure 3A). OD15 MNP with a comparable core size (15 nm) but coated either with DMSA or PEG showed almost the same ratio of SAR reduction after immobilization in PVA. Only marginal differences in SAR values of OD15 MNP with different hydrodynamic diameters and coated with PEG of different molecular weight (PEG5000: 210 nm, 5 kDa; PEG20000: 148 nm, 20 kDa) after PVA immobilization were observed. In contrast to a coating with PEG5000, the utilization of high molecular weight PEG (PEG20000) as surface coating led to comparatively higher SAR values after agarose immobilization (Figure 3B). The observed differences in absolute SAR values of fluidic OD15 MNP coated either with DMSA or PEG (Figure 3A, B) were related to the nature of the synthesis process of the uncoated MNP and varied among different batches. Hence, different SAR values after immobilization were seen. Nevertheless, the ratio of SAR reduction between different viscous immobilization media, especially in water and PVA, remained unchanged. Therefore, the coating with DMSA and PEG did not influence the SAR values of the fluidic MNP.


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)

Immobilization in PVA decreases the SAR of singlecore MNP OD15 and MF66. Immobilization in PVA decreases the SAR of single-core MNP OD15 and MF66 by a factor of two compared to the respective water suspensions. SAR values of single core MNP in water suspension and immobilized in 1% agarose and 10% PVA. Additionally, hydrodynamic diameters (Øhydr.) for each MNP type are shown. Values in brackets indicate core size determined by TEM micrographs. Error bars indicate standard deviation of three independent measurements. OD15 coated with dimercaptosuccinic acid (DMSA) (A); OD15 coated with polyethylenglycol (PEG) exhibiting different molecular weights (B); MF66 coated with DMSA, polyacrylic acid (PAA), and PEG10000 (C); and MF66 coated with PEG10000-NH2(D).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Immobilization in PVA decreases the SAR of singlecore MNP OD15 and MF66. Immobilization in PVA decreases the SAR of single-core MNP OD15 and MF66 by a factor of two compared to the respective water suspensions. SAR values of single core MNP in water suspension and immobilized in 1% agarose and 10% PVA. Additionally, hydrodynamic diameters (Øhydr.) for each MNP type are shown. Values in brackets indicate core size determined by TEM micrographs. Error bars indicate standard deviation of three independent measurements. OD15 coated with dimercaptosuccinic acid (DMSA) (A); OD15 coated with polyethylenglycol (PEG) exhibiting different molecular weights (B); MF66 coated with DMSA, polyacrylic acid (PAA), and PEG10000 (C); and MF66 coated with PEG10000-NH2(D).
Mentions: In general, the immobilization of MNP in PVA resulted in decreased SAR values compared to MNP suspended in water, independently of their core structure, core size, and hydrodynamic diameter. Moreover, SAR values were reduced approximately by a factor of two after PVA immobilization in comparison to MNP suspended in water. The embedment of MNP in 1% agarose led to higher SAR values than the immobilization in 10% PVA, confirming a weaker immobilization of MNP in agarose than in PVA.The single core OD15 MNP, which were coated with DMSA and suspended in water, exhibited SAR values of 658 W/g Fe. Immobilization in 1% agarose decreased SAR to approximately 84% (550 W/g Fe). Lowest SAR values (382 W/g Fe) were observed after immobilization in PVA (Figure 3A). OD15 MNP with a comparable core size (15 nm) but coated either with DMSA or PEG showed almost the same ratio of SAR reduction after immobilization in PVA. Only marginal differences in SAR values of OD15 MNP with different hydrodynamic diameters and coated with PEG of different molecular weight (PEG5000: 210 nm, 5 kDa; PEG20000: 148 nm, 20 kDa) after PVA immobilization were observed. In contrast to a coating with PEG5000, the utilization of high molecular weight PEG (PEG20000) as surface coating led to comparatively higher SAR values after agarose immobilization (Figure 3B). The observed differences in absolute SAR values of fluidic OD15 MNP coated either with DMSA or PEG (Figure 3A, B) were related to the nature of the synthesis process of the uncoated MNP and varied among different batches. Hence, different SAR values after immobilization were seen. Nevertheless, the ratio of SAR reduction between different viscous immobilization media, especially in water and PVA, remained unchanged. Therefore, the coating with DMSA and PEG did not influence the SAR values of the fluidic MNP.

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