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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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Schematics of the self-assembly of MNPs and virus particles into MNP-VP complexes.
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Figure 2: Schematics of the self-assembly of MNPs and virus particles into MNP-VP complexes.

Mentions: Selected MNPs exhibited similar core diameters (PEI-Mag = 9.0 nm and SO-Mag = 6.7 nm). The saturation magnetization of the core material at RT was 62 and 94 Am2/kg (Fe), resulting in an average magnetic moment of the insulated particles of 5.8 x 10-20 and 8.7 x 10-20 Am2 for the PEI-Mag and the SO-Mag MNPs, respectively 37, 49. Surface coating of PEI-Mag MNPs with a self-assembling layer comprising 32 mass% polyetheleneimine (PEI) and 68 mass% of the fluorinated surfactant Zonyl-FSA (figure 1A and C) resulted in a mean hydrodynamic diameter (Dh) of 28 ± 2 nm. In contrast, decoration of SO-Mag MNPs with PEI resulted in SiOx/Phosphonate-PEI coating of 11.5 w/w% PEI-to-iron 38 (shown schematically in figure 1B) with a silica coating width of approximately 1 nm and a higher mean Dh of 76 ± 27 nm, suggesting small aggregate formation. In addition, PEI coating led to a highly positive electrokinetic potential (ζ) for both MNPs (55.0 ± 0.7 mV for PEI-Mag and 40.4 ± 0.4 mV for SO-Mag). The decreased potential of the SO-Mag particles compared to the PEI-Mag particles is due to the lower PEI content and the negatively charged surface phosphonate groups decorating the silica coating. On the other hand, mean Dh of selected viruses, Ad and VSV, were 123 ± 33 nm and 175 ± 61 nm, and both viruses exhibited a negative ζ (-9.1 ± 1.3 mV and -11.8 ± 0.7 mV, respectively), enabling self-assembly of MNPs and VPs by electrostatic interactions. Complex formation with PEI-Mag resulted in a net positive charge of the magnetic viral complexes (PEI-Mag-Ad ζ = 14.1 ± 2.2 mV and PEI-Mag-VSV ζ = 15.1 ± 0.8 mV). Co-assembly of SO-Mag with Ad also resulted in a net positive charge (SO-Mag-Ad ζ = 13.6 ± 0.4 mV), while a net negative charge was detected with VSV (SO-Mag-VSV ζ = -7.1 ± 0.8 mV). ζ and Dh measurements of the different MNP-VP complex suspensions showed neither free MNPs nor naked VPs (data not shown). As expected, MNP-VP complexes were larger compared to naked VPs and larger for SO-Mag- compared to PEI-Mag-based complexes (PEI-Mag-Ad Dh = 271 ± 178 and PEI-Mag-VSV Dh = 514 ± 99 nm; SO-Mag-Ad Dh = 609 ± 127 nm and SO-Mag-VSV Dh = 923 ± 120 nm), the latter results suggesting aggregate formation of SO-Mag-VP complexes in PBS suspensions as well. Figure 2 shows a schematic of self-assembly of MNPs and VPs and the resulting magnetic viral complexes and table 2 summarizes their physico-chemical properties.


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)

Schematics of the self-assembly of MNPs and virus particles into MNP-VP complexes.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 2: Schematics of the self-assembly of MNPs and virus particles into MNP-VP complexes.
Mentions: Selected MNPs exhibited similar core diameters (PEI-Mag = 9.0 nm and SO-Mag = 6.7 nm). The saturation magnetization of the core material at RT was 62 and 94 Am2/kg (Fe), resulting in an average magnetic moment of the insulated particles of 5.8 x 10-20 and 8.7 x 10-20 Am2 for the PEI-Mag and the SO-Mag MNPs, respectively 37, 49. Surface coating of PEI-Mag MNPs with a self-assembling layer comprising 32 mass% polyetheleneimine (PEI) and 68 mass% of the fluorinated surfactant Zonyl-FSA (figure 1A and C) resulted in a mean hydrodynamic diameter (Dh) of 28 ± 2 nm. In contrast, decoration of SO-Mag MNPs with PEI resulted in SiOx/Phosphonate-PEI coating of 11.5 w/w% PEI-to-iron 38 (shown schematically in figure 1B) with a silica coating width of approximately 1 nm and a higher mean Dh of 76 ± 27 nm, suggesting small aggregate formation. In addition, PEI coating led to a highly positive electrokinetic potential (ζ) for both MNPs (55.0 ± 0.7 mV for PEI-Mag and 40.4 ± 0.4 mV for SO-Mag). The decreased potential of the SO-Mag particles compared to the PEI-Mag particles is due to the lower PEI content and the negatively charged surface phosphonate groups decorating the silica coating. On the other hand, mean Dh of selected viruses, Ad and VSV, were 123 ± 33 nm and 175 ± 61 nm, and both viruses exhibited a negative ζ (-9.1 ± 1.3 mV and -11.8 ± 0.7 mV, respectively), enabling self-assembly of MNPs and VPs by electrostatic interactions. Complex formation with PEI-Mag resulted in a net positive charge of the magnetic viral complexes (PEI-Mag-Ad ζ = 14.1 ± 2.2 mV and PEI-Mag-VSV ζ = 15.1 ± 0.8 mV). Co-assembly of SO-Mag with Ad also resulted in a net positive charge (SO-Mag-Ad ζ = 13.6 ± 0.4 mV), while a net negative charge was detected with VSV (SO-Mag-VSV ζ = -7.1 ± 0.8 mV). ζ and Dh measurements of the different MNP-VP complex suspensions showed neither free MNPs nor naked VPs (data not shown). As expected, MNP-VP complexes were larger compared to naked VPs and larger for SO-Mag- compared to PEI-Mag-based complexes (PEI-Mag-Ad Dh = 271 ± 178 and PEI-Mag-VSV Dh = 514 ± 99 nm; SO-Mag-Ad Dh = 609 ± 127 nm and SO-Mag-VSV Dh = 923 ± 120 nm), the latter results suggesting aggregate formation of SO-Mag-VP complexes in PBS suspensions as well. Figure 2 shows a schematic of self-assembly of MNPs and VPs and the resulting magnetic viral complexes and table 2 summarizes their physico-chemical properties.

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