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Characterization of magnetic viral complexes for targeted delivery in oncology.

Almstätter I, Mykhaylyk O, Settles M, Altomonte J, Aichler M, Walch A, Rummeny EJ, Ebert O, Plank C, Braren R - Theranostics (2015)

Bottom Line: Assembly and cell internalization of MNP-VP complexes resulted in 81 - 97 % reduction of r2 and 35 - 82 % increase of r2(*) compared to free MNPs.In a proof-of-principle study the non-invasive detection of MNP-VPs by MRI was shown in vivo in an orthotopic rat hepatocellular carcinoma model.In conclusion, MNP assembly and compartmentalization have a major impact on relaxivities, therefore calibration measurements are required for the correct quantification in biodistribution studies.

View Article: PubMed Central - PubMed

Affiliation: 1. Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar der Technischen Universität München, Munich, Germany;

ABSTRACT
Oncolytic viruses are promising new agents in cancer therapy. Success of tumor lysis is often hampered by low intra-tumoral titers due to a strong anti-viral host immune response and insufficient tumor targeting. Previous work on the co-assembly of oncolytic virus particles (VPs) with magnetic nanoparticles (MNPs) was shown to provide shielding from inactivating immune response and improve targeting by external field gradients. In addition, MNPs are detected by magnet resonance imaging (MRI) enabling non-invasive therapy monitoring. In this study two selected core-shell type iron oxide MNPs were assembled with adenovirus (Ad) or vesicular stomatitis virus (VSV). The selected MNPs were characterized by high r2 and r2(*) relaxivities and thus could be quantified non-invasively by 1.5 and 3.0 tesla MRI with a detection limit below 0.001 mM iron in tissue-mimicking phantoms. Assembly and cell internalization of MNP-VP complexes resulted in 81 - 97 % reduction of r2 and 35 - 82 % increase of r2(*) compared to free MNPs. The relaxivity changes could be attributed to the clusterization of particles and complexes shown by transmission electron microscopy (TEM). In a proof-of-principle study the non-invasive detection of MNP-VPs by MRI was shown in vivo in an orthotopic rat hepatocellular carcinoma model. In conclusion, MNP assembly and compartmentalization have a major impact on relaxivities, therefore calibration measurements are required for the correct quantification in biodistribution studies. Furthermore, our study provides first evidence of the in vivo applicability of selected MNP-VPs in cancer therapy.

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r2 and r2* relaxivity plots. In the panels A and C transverse relaxation rate R2, in the panels B and D the spin-spin relaxation rate R2* are each plotted against the respective iron concentrations. The data of panels A and B were acquired at 1.5 T, the data of panels C and D show the corresponding data acquired at 3 T, both on clinical MRI systems. In each panel, the left graphs show the data for Ad and RDB cells, the right graphs the data for VSV and McA cells, the top graphs show the datasets for PEI-Mag particles and the bottom graphs for SO-Mag particles. Free MNPs are plotted in black, cell internalized MNPs in red, and free complexes in blue and cell internalized complexes in purple.
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Figure 8: r2 and r2* relaxivity plots. In the panels A and C transverse relaxation rate R2, in the panels B and D the spin-spin relaxation rate R2* are each plotted against the respective iron concentrations. The data of panels A and B were acquired at 1.5 T, the data of panels C and D show the corresponding data acquired at 3 T, both on clinical MRI systems. In each panel, the left graphs show the data for Ad and RDB cells, the right graphs the data for VSV and McA cells, the top graphs show the datasets for PEI-Mag particles and the bottom graphs for SO-Mag particles. Free MNPs are plotted in black, cell internalized MNPs in red, and free complexes in blue and cell internalized complexes in purple.

Mentions: MRI was performed to determine the MR detection limit for the non-invasive monitoring of MNP and MNP-VP complexes and to quantify the effect of cluster formation or intracellular compartmentalization on measured tissue relaxivities. The visual iron detection limit in the R2* maps was as low as 0.003 - 0.008 mM Fe, equaling 0.76 x 105 labeled cells per mL at a loading of 2.5 pg iron per cell, 0.24 x 105 labeled cells per mL at a loading of 6.7 pg iron per cell, or 0.36 x 105 labeled cells per mL at a loading of 5.4 pg iron per cell. The MR detection limit could not be determined as all dilutions of the magnetic nanomaterial were clearly detectable above the background of mimicked liver tissue and untreated carcinoma cells, and therefore it was below 0.001 mM Fe, the lowest measured iron dilution. Figure 7 compiles image sets of exemplary phantoms with (a photograph,) a T2* echo image, and the corresponding R2* map. Figure 7A shows the phantom with homogenously dispersed PEI-Mag particles, panel 7B shows the phantom prepared with SO-Mag-VSV complexes internalized in McA cells and the image set 7C shows the background phantom of untreated McA cells with no detectable iron signal. The fading brown color in the photograph, the black-to-grey signal increase and the red-to-blue signal transition in the R2* map in all three panels mirror the decrease of magnetic material due to the dilution. Both, the R2 and the R2* relaxation rates linearly increased with increasing iron concentrations in the range of 0.001 to 0.34 mM Fe of free, assembled and intracellular MNPs. The measured R2 or R2* transverse relaxation rates and respective iron concentrations are plotted in figure 8 for the 1.5 T (8A and 8B) and 3 T (8C and 8D) data and table 5 summarizes the calculated r2 and r2* relaxivities, ratios of the complexed and/or internalized MNPs relative to the free MNPs, iron loading per cell and r2*/r2 ratios acquired on a 1.5 T clinical MRI system (corresponding 3 T data in Supplementary Material: table S2). Calculated r2* values were higher than r2 values and SO-Mag exhibited higher r2* relaxivities compared to PEI-Mag MNPs, while the r2 relaxivities were in the same range. Internalized or complexed MNPs yielded lower r2 values compared to freely dispersed MNPs. In contrast, r2* relaxivities increased after nanoassembly and/or cell internalization. Supplementary Material: figure S1 clearly demonstrates the comparability of data acquired either on a 1.5 T or a 3 T clinical MRI system.


Characterization of magnetic viral complexes for targeted delivery in oncology.

Almstätter I, Mykhaylyk O, Settles M, Altomonte J, Aichler M, Walch A, Rummeny EJ, Ebert O, Plank C, Braren R - Theranostics (2015)

r2 and r2* relaxivity plots. In the panels A and C transverse relaxation rate R2, in the panels B and D the spin-spin relaxation rate R2* are each plotted against the respective iron concentrations. The data of panels A and B were acquired at 1.5 T, the data of panels C and D show the corresponding data acquired at 3 T, both on clinical MRI systems. In each panel, the left graphs show the data for Ad and RDB cells, the right graphs the data for VSV and McA cells, the top graphs show the datasets for PEI-Mag particles and the bottom graphs for SO-Mag particles. Free MNPs are plotted in black, cell internalized MNPs in red, and free complexes in blue and cell internalized complexes in purple.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4402492&req=5

Figure 8: r2 and r2* relaxivity plots. In the panels A and C transverse relaxation rate R2, in the panels B and D the spin-spin relaxation rate R2* are each plotted against the respective iron concentrations. The data of panels A and B were acquired at 1.5 T, the data of panels C and D show the corresponding data acquired at 3 T, both on clinical MRI systems. In each panel, the left graphs show the data for Ad and RDB cells, the right graphs the data for VSV and McA cells, the top graphs show the datasets for PEI-Mag particles and the bottom graphs for SO-Mag particles. Free MNPs are plotted in black, cell internalized MNPs in red, and free complexes in blue and cell internalized complexes in purple.
Mentions: MRI was performed to determine the MR detection limit for the non-invasive monitoring of MNP and MNP-VP complexes and to quantify the effect of cluster formation or intracellular compartmentalization on measured tissue relaxivities. The visual iron detection limit in the R2* maps was as low as 0.003 - 0.008 mM Fe, equaling 0.76 x 105 labeled cells per mL at a loading of 2.5 pg iron per cell, 0.24 x 105 labeled cells per mL at a loading of 6.7 pg iron per cell, or 0.36 x 105 labeled cells per mL at a loading of 5.4 pg iron per cell. The MR detection limit could not be determined as all dilutions of the magnetic nanomaterial were clearly detectable above the background of mimicked liver tissue and untreated carcinoma cells, and therefore it was below 0.001 mM Fe, the lowest measured iron dilution. Figure 7 compiles image sets of exemplary phantoms with (a photograph,) a T2* echo image, and the corresponding R2* map. Figure 7A shows the phantom with homogenously dispersed PEI-Mag particles, panel 7B shows the phantom prepared with SO-Mag-VSV complexes internalized in McA cells and the image set 7C shows the background phantom of untreated McA cells with no detectable iron signal. The fading brown color in the photograph, the black-to-grey signal increase and the red-to-blue signal transition in the R2* map in all three panels mirror the decrease of magnetic material due to the dilution. Both, the R2 and the R2* relaxation rates linearly increased with increasing iron concentrations in the range of 0.001 to 0.34 mM Fe of free, assembled and intracellular MNPs. The measured R2 or R2* transverse relaxation rates and respective iron concentrations are plotted in figure 8 for the 1.5 T (8A and 8B) and 3 T (8C and 8D) data and table 5 summarizes the calculated r2 and r2* relaxivities, ratios of the complexed and/or internalized MNPs relative to the free MNPs, iron loading per cell and r2*/r2 ratios acquired on a 1.5 T clinical MRI system (corresponding 3 T data in Supplementary Material: table S2). Calculated r2* values were higher than r2 values and SO-Mag exhibited higher r2* relaxivities compared to PEI-Mag MNPs, while the r2 relaxivities were in the same range. Internalized or complexed MNPs yielded lower r2 values compared to freely dispersed MNPs. In contrast, r2* relaxivities increased after nanoassembly and/or cell internalization. Supplementary Material: figure S1 clearly demonstrates the comparability of data acquired either on a 1.5 T or a 3 T clinical MRI system.

Bottom Line: Assembly and cell internalization of MNP-VP complexes resulted in 81 - 97 % reduction of r2 and 35 - 82 % increase of r2(*) compared to free MNPs.In a proof-of-principle study the non-invasive detection of MNP-VPs by MRI was shown in vivo in an orthotopic rat hepatocellular carcinoma model.In conclusion, MNP assembly and compartmentalization have a major impact on relaxivities, therefore calibration measurements are required for the correct quantification in biodistribution studies.

View Article: PubMed Central - PubMed

Affiliation: 1. Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar der Technischen Universität München, Munich, Germany;

ABSTRACT
Oncolytic viruses are promising new agents in cancer therapy. Success of tumor lysis is often hampered by low intra-tumoral titers due to a strong anti-viral host immune response and insufficient tumor targeting. Previous work on the co-assembly of oncolytic virus particles (VPs) with magnetic nanoparticles (MNPs) was shown to provide shielding from inactivating immune response and improve targeting by external field gradients. In addition, MNPs are detected by magnet resonance imaging (MRI) enabling non-invasive therapy monitoring. In this study two selected core-shell type iron oxide MNPs were assembled with adenovirus (Ad) or vesicular stomatitis virus (VSV). The selected MNPs were characterized by high r2 and r2(*) relaxivities and thus could be quantified non-invasively by 1.5 and 3.0 tesla MRI with a detection limit below 0.001 mM iron in tissue-mimicking phantoms. Assembly and cell internalization of MNP-VP complexes resulted in 81 - 97 % reduction of r2 and 35 - 82 % increase of r2(*) compared to free MNPs. The relaxivity changes could be attributed to the clusterization of particles and complexes shown by transmission electron microscopy (TEM). In a proof-of-principle study the non-invasive detection of MNP-VPs by MRI was shown in vivo in an orthotopic rat hepatocellular carcinoma model. In conclusion, MNP assembly and compartmentalization have a major impact on relaxivities, therefore calibration measurements are required for the correct quantification in biodistribution studies. Furthermore, our study provides first evidence of the in vivo applicability of selected MNP-VPs in cancer therapy.

Show MeSH
Related in: MedlinePlus