Multimodality imaging using SPECT/CT and MRI and ligand functionalized 99m

BACKGROUND: In the present study, we used multimodal imaging to investigate biodistribution in rats after intravenous administration of a new 99mTc-labeled delivery system consisting of polymer-shelled microbubbles (MBs) functionalized with diethylenetriaminepentaacetic acid (DTPA), thiolated poly(methacrylic acid) (PMAA), chitosan, 1,4,7-triacyclononane-1,4,7-triacetic acid (NOTA), NOTA-super paramagnetic iron oxide nanoparticles (SPION), or DTPA-SPION. METHODS: Examinations utilizing planar dynamic scintigraphy and hybrid imaging were performed using a commercially available single-photon emission computed tomography (SPECT)/computed tomography (CT) system. For SPION containing MBs, the biodistribution pattern of 99mTc-labeled NOTA-SPION and DTPA-SPION MBs was investigated and co-registered using fusion SPECT/CT and magnetic resonance imaging (MRI). Moreover, to evaluate the biodistribution, organs were removed and radioactivity was measured and calculated as percentage of injected dose. RESULTS: SPECT/CT and MRI showed that the distribution of 99mTc-labeled ligand-functionalized MBs varied with the type of ligand as well as with the presence of SPION. The highest uptake was observed in the lungs 1 h post injection of 99mTc-labeled DTPA and chitosan MBs, while a similar distribution to the lungs and the liver was seen after the administration of PMAA MBs. The highest counts of 99mTc-labeled NOTA-SPION and DTPA-SPION MBs were observed in the lungs, liver, and kidneys 1 h post injection. The highest counts were observed in the liver, spleen, and kidneys as confirmed by MRI 24 h post injection. Furthermore, the results obtained from organ measurements were in good agreement with those obtained from SPECT/CT. CONCLUSIONS: In conclusion, microbubbles functionalized by different ligands can be labeled with radiotracers and utilized for SPECT/CT imaging, while the incorporation of SPION in MB shells enables imaging using MR. Our investigation revealed that biodistribution may be modified using different ligands. Furthermore, using a single contrast agent with fusion SPECT/CT/MR multimodal imaging enables visualization of functional and anatomical information in one image, thus improving the diagnostic benefit for patients

Biodistribution, kinetics, and biological fate of SPION microbubbles in the rat

Åsa Barrefelt,1,2,* Maryam Saghafian,2,* Raoul Kuiper,3 Fei Ye,4 Gabriella Egri,5 Moritz Klickermann,5 Torkel B Brismar,1 Peter Aspelin,1 Mamoun Muhammed,4 Lars Dähne,5 Moustapha Hassan2,6 1Department of Clinical Science, Intervention and Technology, Division of Medical Imaging and Technology, Karolinska Institutet, and Department of Radiology, Karolinska University Hospital-Huddinge, Stockholm, Sweden; 2Experimental Cancer Medicine, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden; 3Karolinska Institute Core Facility for Morphologic Phenotype Analysis, Clinical Research Center, Karolinska University Hospital-Huddinge, Stockholm, Sweden; 4Division of Functional Materials, Department of Materials and Nano Physics, Royal Institute of Technology, Stockholm, Sweden; 5Surflay Nanotec GmbH, Berlin, Germany; 6Clinical Research Center, Karolinska University Hospital-Huddinge, Stockholm, Sweden *These authors contributed equally to this work Background: In the present investigation, we studied the kinetics and biodistribution of a contrast agent consisting of poly(vinyl alcohol) (PVA) microbubbles containing superparamagnetic iron oxide (SPION) trapped between the PVA layers (SPION microbubbles). Methods: The biological fate of SPION microbubbles was determined in Sprague-Dawley rats after intravenous administration. Biodistribution and elimination of the microbubbles were studied in rats using magnetic resonance imaging for a period of 6 weeks. The rats were sacrificed and perfusion-fixated at different time points. The magnetic resonance imaging results obtained were compared with histopathologic findings in different organs. Results: SPION microbubbles could be detected in the liver using magnetic resonance imaging as early as 10 minutes post injection. The maximum signal was detected between 24 hours and one week post injection. Histopathology showed the presence of clustered SPION microbubbles predominantly in the lungs from the first time point investigated (10 minutes). The frequency of microbubbles declined in the pulmonary vasculature and increased in pulmonary, hepatic, and splenic macrophages over time, resulting in a relative shift from the lungs to the spleen and liver. Meanwhile, macrophages showed increasing signs of cytoplasmic iron accumulation, initially in the lungs, then followed by other organs. Conclusion: The present investigation highlights the biological behavior of SPION microbubbles, including organ distribution over time and indications for biodegradation. The present results are essential for developing SPION microbubbles as a potential contrast agent and/or a drug delivery vehicle for specific organs. Such a vehicle will facilitate the use of multimodality imaging techniques, including ultrasound, magnetic resonance imaging, and single positron emission computed tomography, and hence improve diagnostics, therapy, and the ability to monitor the efficacy of treatment. Keywords: biodistribution, microbubbles, superparamagnetic iron oxide, pharmacokinetics, magnetic resonance imaging, histopatholog

Dynamic MR Imaging, Biodistribution and Pharmacokinetics of Polymer Shelled Microbubbles Containing Spion

Biodistribution and pharmacokinetics of polymer shelled microbubbles (MBs), embedded with superparamagnetic iron oxide nanoparticles (SPION) in the shell, were determined in rats using dynamic Magnetic Resonance (MR) imaging. The histological survey of tissue samples showed that SPION MBs were taken up by macrophages in the lungs, spleen and liver. The elimination half-life of SPION MBs was longer than that of SPION. This study shows that MRI is a reliable and non-invasive method for pharmacokinetic calculations

Membrane protein isolation by in situ solubilization, partitioning and affinity adsorption in aqueous two-phase systems - Purification of the human type 1 11 beta-hydroxysteroid dehydrogenase

Recently developed aqueous two-phase systems based on non-ionic detergents and polymers are suitable for the separation of membrane proteins. Moreover, within this relatively membrane protein "friendly" environment, changes in temperature can be controlled and stabilizing agents may be added to ensure integrity of the target protein during isolation. Here, we use aqueous two-phase partitioning for the isolation of membrane bound I I p-hydroxysteroid dehydrogenase type I (11beta-HSD1). Different detergents were used to find optimal conditions regarding solubilization and retaining target protein activity. We explored in situ solubilization by adding detergent directly to the aqueous two-phase system, as well as a batch metal affinity capture step of 6xHis tagged 11beta-HSD1 in the two-phase system. The use of detergent/polymer two-phase systems resulted in a specific enzyme activity of 3840 nmol mg(-1) min(-1) of the target membrane protein compared to a conventional purification protocol where a specific enzyme activity of 1440 nmol mg(-1) min(-1) was achieved. (C) 2004 Elsevier B.V. All rights reserved

Magnetite Nanoparticles Can Be Coupled to Microbubbles to Support Multimodal Imaging

Microbubbles (MBs) are commonly used as injectable ultrasound contrast agent (UCA) in modern ultrasonography. Polymer-shelled UCAs present additional potentialities with respect to marketed lipid-shelled UCAs. They are more robust; that is, they have longer shelf and circulation life, and surface modifications are quite easily accomplished to obtain enhanced targeting and local drug delivery. The next generation of UCAs will be required to support not only ultrasound-based imaging methods but also other complementary diagnostic approaches such as magnetic resonance imaging or computer tomography. This work addresses the features of MBs that could function as contrast agents for both ultrasound and magnetic resonance imaging. The results indicate that the introduction of iron oxide nanoparticles (SPIONs) in the poly(vinyl alcohol) shell or on the external surface of the MBs does not greatly decrease the echogenicity of the host MBs compared with the unmodified one. The presence of SPIONs provides enough magnetic susceptibility to the MBs to accomplish good detectability both in vitro and in vivo. The distribution of SPIONs on the shell and their aggregation state seem to be key factors for the optimization of the transverse relaxation rate