Heating of magnetic nanoparticles under gradual immobilization in hydrogels
- The heat generated by magnetic nanoparticles (MNP) forms the basis of magnetic fluid hyperthermia (MFH) tumor therapy and arises from MNP magnetic moments relaxing in an alternating magnetic field. In physiological environments MNP strongly interact with cells, binding to their membranes as well as internalizing inside lysosomes, which alters the MNP magnetic relaxation. In the present study, we investigate the heating behavior of MNP in-vitro for different binding states and compare it to the heating of trapped MNP in dedicated hydrogels of different mesh size, mimicking different immobilization states. We used iron-oxide MNP (mean core size 10 nm) with a biocompatible phospholipid coating, referred to as magnetoliposomes (ML), for in-vitro studies, and with citric acid coating (CA-MNP) for studies in hydrogels. All samples were subjected to an AMF (40 kA/m, 270 kHz) for 30 min, and from the recorded time-temperature curve, the specific loss power (SLP) value was calculated. In-vitro experiments were performed with L929 cells, which were incubated for 24 h with 225 μg(Fe)/mL ML dispersed in RPMI cell medium. The results of the SLP values were analyzed regarding the internalized ML amount with respect to ML residuals in RMPI medium and compared to fully immobilized ML after freeze-drying (FD): The SLP value of 10.1 % intracellular ML decreased by 20 %, the SLP value of 100 % intracellular ML decreased by 60 % and that of FD-ML decreased by 70 % (Fig 1a). The influence of gradual immobilization of MNP on the heating was investigated by mixing CA-MNP in low-melting agarose and polyacrylamide hydrogels. In agarose and polyacrylamide gels the mean mesh size can be tuned via the amount of monomers and cross-linkers, respectively, and in this way the state of MNP immobilization is influenced. SLP values decreased by up to 40 % in agarose gels for mesh sizes smaller than the hydrodynamic size dH = 20.6 nm. A comparable decrease was observed in polyacrylamide gels (Fig 1b & c). We attribute this drop in SLP values to a gradual immobilization of MNP trapped in the hydrogels, which blocks particle relaxation and therefore decreases heating efficiency. This agrees very well with the results of the in-vitro measurements. The relative difference in the SLP drop in agarose and polyacrylamide hydrogels for similar mesh sizes might be explained by their gel-specific microstructures, which influence the MNP freedom of movement. For validation of these results, further investigations of the relaxation behavior of such trapped MNP via magnetic particle spectroscopy are currently under progress.
Author: | Ulrich M. EngelmannORCiD, Benedikt Mues, Julian Seifert, Annette Schmidt, Ioana Slabu |
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Parent Title (English): | 12th International Conference on the Scientific and Clinical Applications of Magnetic Carriers |
Document Type: | Conference Poster |
Language: | English |
Year of Completion: | 2018 |
First Page: | 51 |
Note: | 12th International Conference on the Scientific and Clinical Applications of Magnetic Carriers, Copenhagen, Denmark, May 22-26 2018 Poster 9 |
Note: | Corresponding author: Ulrich M. Engelmann |
Link: | https://magneticmicrosphere.com/ckfinder/userfiles/files/Magmeet2018AB.pdf |
Zugriffsart: | weltweit |
Institutes: | FH Aachen / Fachbereich Medizintechnik und Technomathematik |