Molecular magnetic resonance imaging of Alpha-v-Beta-3 integrin expression in tumors with ultrasound microbubbles

Vertika Pathak; Teresa Nolte; Elena Rama; Anne Rix; Seyed Mohammadali Dadfar; Vera Paefgen; Srinivas Banala; Eva Miriam Buhl; Marek Weiler; Volkmar Schulz; Twan Lammers; Fabian Kiessling

doi:10.1016/j.biomaterials.2021.120896

Molecular magnetic resonance imaging of Alpha-v-Beta-3 integrin expression in tumors with ultrasound microbubbles

Biomaterials. 2021 Aug:275:120896. doi: 10.1016/j.biomaterials.2021.120896. Epub 2021 May 27.

Affiliations

¹ Institute for Experimental Molecular Imaging, RWTH Aachen University, 52074, Aachen, Germany.
² Electron Microscope Facility, University Hospital RWTH, RWTH Aachen University, 52074, Aachen, Germany.
³ Institute for Experimental Molecular Imaging, RWTH Aachen University, 52074, Aachen, Germany. Electronic address: fkiessling@ukaachen.de.

PMID: 34090049
DOI: 10.1016/j.biomaterials.2021.120896

Abstract

Microbubbles (MB) are used as ultrasound (US) contrast agents and can be efficiently targeted against markers of angiogenesis and inflammation. Due to their gas core, MB locally alter susceptibilities in magnetic resonance imaging (MRI), but unfortunately, the resulting contrast is low and not sufficient to generate powerful molecular MRI probes. Therefore, we investigated whether a potent molecular MR agent can be generated by encapsulating superparamagnetic iron oxide nanoparticles (SPION) in the polymeric shell of poly (n-butylcyanoacrylate) (PBCA) MB and targeted them against α_vβ₃ integrins on the angiogenic vasculature of 4T1 murine breast carcinomas. SPION-MB consist of an air core and a multi-layered polymeric shell enabling efficient entrapment of SPION. The mean size of SPION-MB was 1.61 ± 0.32 μm. Biotin-streptavidin coupling was employed to functionalize the SPION-MB with cyclic RGDfK (Arg-Gly-Asp) and RADfK (Arg-Ala-Asp) peptides. Cells incubated with RGD-SPION-MB showed enhanced transverse relaxation rates compared with SPION-MB and blocking α_vβ₃ integrin receptors with excess free cRGDfK significantly reduced RGD-SPION-MB binding. Due to the fast binding of RGD-SPION-MB in vivo, dynamic susceptibility contrast MRI was employed to track their retention in tumors in real-time. Higher retention of RGD-SPION-MB was observed compared with SPION-MB and RAD-SPION-MB. To corroborate our MRI results, molecular US was performed the following day using the destruction-replenishment method. Both imaging modalities consistently indicated higher retention of RGD-SPION-MB in angiogenic vessels compared with SPION-MB and RAD-SPION-MB. Competitive blocking experiments in mice further confirmed that the binding of RGD-SPION-MB to α_vβ₃ integrin receptors is specific. Overall, this study demonstrates that RGD-SPION-MB can be employed as molecular MR/US contrast agents and are capable of assessing the α_vβ₃ integrin expression in the neovasculature of malignant tumors.

Keywords: Angiogenesis; MRI; Microbubbles; Molecular imaging; Ultrasound.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Integrin alphaV
Integrin alphaVbeta3
Magnetic Resonance Imaging
Mice
Microbubbles*
Neoplasms*
Ultrasonography

Substances

Integrin alphaV
Integrin alphaVbeta3