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  • Oral presentation
  • Open Access

High-Gd-Payload P22 protein cage nanoparticles for imaging vascular inflammation

  • 1,
  • 2,
  • 2,
  • 2,
  • 2 and
  • 1
Journal of Cardiovascular Magnetic Resonance201315 (Suppl 1) :O66

https://doi.org/10.1186/1532-429X-15-S1-O66

  • Published:

Keywords

  • Double Inversion Recovery
  • Amine Functional Group
  • Carotid Ligation
  • Nanoparticle Platform
  • Maximum Plaque

Background

The bacteriophage P22 protein cage can be bioengineered to contain a high-relaxivity gadolinium (Gd) payload internally and targeting ligands externally. It also enables phage-library-based identification of novel targets. Thus, P22 may have advantages for molecular/cellular imaging by MRI.

Methods

1) P22: The P22 protein cage (60 nm) is bioengineered with an internal polymer network with amine functional groups allowing incorporation of ~9100 Gd-DTPA molecules per cage via the amine groups (Figure 1: [1]). This provides a per cage relaxivity of 70000 mM-1s-1, superior to Gd-DTPA for the equivalent Gd concentration.

Figure 1

2) Atherosclerosis Models: Both ApoE-deficient (ApoE-/-) and FVB mice were used. ApoE-/- mice develop atherosclerosis enhanced by high-fat diet. FVB mice develop macrophage-rich carotid lesions with carotid ligation in combination with high-fat diet and diabetes induction [2].

3) P22-polymer-Gd in vivo MR imaging: Mice were injected intravenously with P22-polymer-Gd (N=5, 20 µmol Gd/kg, one-fifth the typical clinical dose) or Magnevist (N=1, 20 µmol Gd/kg). Vascular MRA at 1T was performed (Aspect M2TM, 500 mT/m, 2500 T/m/s) using 3D-SPGR (TR/TE=12 ms/2.1 ms, slice thickness=1 mm, FOV=5 cm, matrix=128x128, FA=45). Vessel wall MRI at 3T was performed (Signa HDx, GE Healthcare, 50mT/m, 150 T/m/s) with a phased-array mouse coil (RAPID MR International), using a double inversion recovery fast spin echo sequence (TR/TE= 400 ms/15 ms, slice thickness=1mm, FOV=3 cm, matrix= 256x256) up to 24 hours after injection.

4) RGD-targeted P22 ex vivo fluorescence imaging: Molecular targeting of P22 was evaluated by attaching RGD peptides externally, which targets the αVβ3 integrin, upregulated on activated macrophages. ApoE-/- mice (N=4) were injected intravenously with RGD+P22 or RGD-P22 (labeled with Cy5.5, 4 nmol/mouse). Forty-eight hours later, ex vivo fluorescence imaging was performed using MaestroTM imaging system (Cri, Woburn, MA). Maximum plaque signal intensities were measured and compared.

Results

Low dose P22-polymer-Gd showed strong enhancement for 1T vascular MRA (Figure 2). It also showed clear enhancement of the aortic wall (ApoE-/-) and ligated carotid (FVB) at 3T (Figure 3). Ex vivo fluorescence imaging showed the accumulation of both RGD+P22 or RGD-P22 in atherosclerotic lesions (Figure 4). RDG targeting enhanced plaque uptake (RGD+P22: 0.025 ± 0.002 counts/sec vs. RGD-P22: 0.005 ± 0.004 counts/sec, p=0.05).

Figure 2

Figure 3

Figure 4

Conclusions

The P22 protein cage nanoparticle demonstrates both internal high-relaxivity Gd-loading for in vivo MRI as well as external RGD-targeting for enhanced uptake in vascular inflammation. Thus, P22 is a novel, multi-functional nanoparticle platform for targeted-imaging of atherosclerosis.

Funding

GE healthcare, Kowa, Inc.

Authors’ Affiliations

(1)
Stanford University, Stanford, CA, USA
(2)
Montana State University, Bozeman, MT, USA

References

  1. Lucon J, et al.: Nat Chem. 2012, 4: 781-788. 10.1038/nchem.1442.PubMed CentralView ArticlePubMedGoogle Scholar
  2. Kosuge, et al.: PLoS One. 2011, 6: e14523-10.1371/journal.pone.0014523.PubMed CentralView ArticlePubMedGoogle Scholar

Copyright

© Kosuge et al; licensee BioMed Central Ltd. 2013

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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