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Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2013.

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Molecular Imaging and Contrast Agent Database (MICAD) [Internet].

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64Cu-1,4,7,10-Tetraazacyclododecane-N,N’,N’’,N’’’-tetraacetic acid-iron oxide-c(RGDyK) nanoparticles

64Cu-DOTA-IO-RGDyK
, PhD
National Center for Biotechnology Information, NLM, NIH

Created: ; Last Update: December 3, 2009.

Chemical name:64Cu-1,4,7,10-Tetraazacyclododecane-N,N’,N’’,N’’’-tetraacetic acid-iron oxide-c(RGDyK) nanoparticles
Abbreviated name:64Cu-DOTA-IO-RGDyK
Synonym:
Agent category:Peptide
Target:Integrin αvβ3
Target category:Receptor-ligand binding
Method of detection:Positron emission tomography (PET), magnetic resonance imaging (MRI)
Source of signal:64Cu and iron oxide
Activation:No
Studies:
  • Checkbox In vitro
  • Checkbox Rodents
Click on protein, nucleotide (RefSeq), and gene for more information about integrin αvβ3.

Background

[PubMed]

Magnetic resonance imaging (MRI) maps information about tissues spatially and functionally. Protons (hydrogen nuclei) are widely used in imaging because of their abundance in water molecules. Water comprises ~80% of most soft tissue. The contrast of proton MRI depends primarily on the density of the nucleus (proton spins), the relaxation times of the nuclear magnetization (T1, longitudinal, and T2, transverse), the magnetic environment of the tissues, and the blood flow to the tissues. However, insufficient contrast between normal and diseased tissues requires the use of contrast agents. Most contrast agents affect the T1 and T2 relaxation times of the surrounding nuclei, mainly the protons of water. T2* is the spin–spin relaxation time composed of variations from molecular interactions and intrinsic magnetic heterogeneities of tissues in the magnetic field (1). Cross-linked iron oxide (CLIO) nanoparticles and other iron oxide formulations affect T2 primarily and lead to decreased signals. On the other hand, the paramagnetic T1 agents, such as gadolinium (Gd3+) and manganese (Mn2+), accelerate T1 relaxation and lead to brighter contrast images.

Integrins are a family of heterodimeric glycoproteins on cell surfaces that mediate diverse biological events involving cell–cell and cell–matrix interactions (2). Integrins consist of an α and a β subunit and are important for cell adhesion and signal transduction. The αvβ3 integrin is the most prominent receptor class affecting tumor growth, tumor invasiveness, metastasis, tumor-induced angiogenesis, inflammation, osteoporosis, and rheumatoid arthritis (3-8). The αvβ3 integrin is strongly expressed on tumor cells and activated endothelial cells. In contrast, expression of αvβ3 integrin is weak on resting endothelial cells and most normal tissues. The αvβ3 antagonists are being studied as antitumor and antiangiogenic agents, and the agonists are being studied as angiogenic agents for coronary angiogenesis (7, 9, 10). The tripeptide sequence Arg-Gly-Asp (RGD) is identified as a recognition motif used by extracellular matrix proteins (vitronectin, fibrinogen, laminin, and collagen) to bind to a variety of integrins including αvβ3. Various radiolabeled cyclic RGD peptides have been introduced for imaging of tumors and tumor angiogenesis (11). 64Cu-1,4,7,10-Tetraazacyclododecane-N,N’,N’’,N’’’-tetraacetic acid-iron oxide-c(RGDyK) (64Cu-DOTA-IO-RGDyK) nanoparticles have been developed as a multimodality probe for positron emission tomography (PET) and MRI of tumor vasculature to study in vivo biodistribution of the tracer in tumor-bearing mice (12). 64Cu-DOTA-IO-RGDyK has been shown to have a high accumulation in the tumor vasculature with little extravastion and predominant liver and spleen accumulation.

Synthesis

[PubMed]

Polyaspartic acid (PASP, 0.3 mmol) in ammonia was added to 0.6 M FeCl3 and 0.3 M FeCl2. The mixture was heated for 1 h at 100°C (12). PASP-Coated nanoparticles were purified with dialysis. DOTA was activated with ethyl-3-dimethylaminopropyl-carbodiimide and sulfo-N-hydroxysuccinimide for 30 min. The activated DOTA (800 nmol) and the bifunctional linker NHS-poly(ethylene glycol-maleimide (1,200 nmol) were added to a solution of PASP-coated nanoparticles (0.039 mmol iron concentration). The mixture was incubated for 60 min at 4°C. c(RGDyK)-SH (1,500 nmol) was incubated with the mixture overnight at room temperature. DOTA-IO-RGDyK nanoparticles were purified with column chromatography and dialysis. DOTA-IO-RGDyK nanoparticles and 64CuCl2 in acetate buffer (pH 6.5) were incubated for 40 min at 40°C. 64Cu-DOTA-IO-RGDyK nanoparticles were isolated with column chromatography. The average size of DOTA-IO-RGDyK nanoparticles was 45 ± 10 nm in buffer as measured with transmission electron microscope. Each particle contained ~35 c(RGDyK) molecules and ~30 DOTA-chelating groups. 64Cu-DOTA-IO-RGDyK nanoparticles had a specific activity of 185 GBq/g of iron (5 Ci/g of iron).

In Vitro Studies: Testing in Cells and Tissues

[PubMed]

Lee et al. (12) performed a competitive cell-binding assay using human glioblastoma U87MG tumor cells (expressing αvβ3). DOTA-IO-RGDyK nanoparticles inhibited the binding of 125I-echistatin in a dose-dependent manner with a 50% inhibition concentration of 34 ± 5 nM, which was ~6-fold lower than that of c(RGDyK). DOTA-IO nanoparticles had no inhibitory effect on the binding assay. IO nanoparticles exhibited a T2 relaxivity r2 value (at 3 T) of 105.5 mM-1s-1, whereas ferumoxide exhibited a r2 value of 151.9 mM-1 s-1.

Animal Studies

Rodents

[PubMed]

Lee et al. (12) used a whole-body PET imaging system to study the accumulation of 3.7 MBq (0.1 mCi) 64Cu-DOTA-IO-c(RGDyK) or 64Cu-DOTA-IO in nude mice bearing U87MG tumors. 64Cu-DOTA-IO-c(RGDyK) (300 µg of iron) was injected intravenously into tumor-bearing mice (n = 3/group). Tumor accumulation of 64Cu-DOTA-IO-c(RGDyK) was 7.9% injected dose/gram (ID/g) at 1 h, 10.1% ID/g at 4 h, and 9.8% ID/g at 21 h. 64Cu-DOTA-IO showed tumor accumulation of <5% ID/g at these time points. There was no difference in accumulation at 4 h in the liver (23% ID/g) and kidney (5% ID/g) between the two nanoparticles. Co-injection of c(RGDyK) (10 mg/kg) with 64Cu-DOTA-IO-c(RGDyK) reduced the tumor radioactivity levels to <4% ID/g at these time points. T2-Weighted MRI studies at 3 T were performed in mice bearing U87MG tumors after intravenous injection of DOTA-IO-c(RGDyK) nanoparticles. There was a greater tumor signal reduction in the mice receiving DOTA-IO-c(RGDyK) nanoparticles as compared with that in mice receiving DOTA-IO nanoparticles or co-injection of DOTA-IO-RGDyK at 4 h after injection. The strong contrast reduction was similar in the liver and spleen for both nanoparticles. Staining of iron in tissue sections confirmed the MRI findings.

Other Non-Primate Mammals

[PubMed]

No publication is currently available.

Non-Human Primates

[PubMed]

No publication is currently available.

Human Studies

[PubMed]

No publication is currently available.

NIH Support

R24 CA93862, P50 CA114747, R01 CA119053, R21 CA102123, R21 CA121842, U54 CA119367

References

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Wang Y.X., Hussain S.M., Krestin G.P. Superparamagnetic iron oxide contrast agents: physicochemical characteristics and applications in MR imaging. Eur Radiol. 2001;11(11):2319–31. [PubMed: 11702180]
2.
Hynes R.O. Integrins: versatility, modulation, and signaling in cell adhesion. Cell. 1992;69(1):11–25. [PubMed: 1555235]
3.
Jin H., Varner J. Integrins: roles in cancer development and as treatment targets. Br J Cancer. 2004;90(3):561–5. [PMC free article: PMC2410157] [PubMed: 14760364]
4.
Varner J.A., Cheresh D.A. Tumor angiogenesis and the role of vascular cell integrin alphavbeta3. Important Adv Oncol. 1996:69–87. [PubMed: 8791129]
5.
Wilder R.L. Integrin alpha V beta 3 as a target for treatment of rheumatoid arthritis and related rheumatic diseases. Ann Rheum Dis. 2002;61 Suppl 2:ii96–9. [PMC free article: PMC1766704] [PubMed: 12379637]
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Grzesik W.J. Integrins and bone--cell adhesion and beyond. Arch Immunol Ther Exp (Warsz) 1997;45(4):271–5. [PubMed: 9523000]
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Kumar C.C. Integrin alpha v beta 3 as a therapeutic target for blocking tumor-induced angiogenesis. Curr Drug Targets. 2003;4(2):123–31. [PubMed: 12558065]
8.
Ruegg C., Dormond O., Foletti A. Suppression of tumor angiogenesis through the inhibition of integrin function and signaling in endothelial cells: which side to target? Endothelium. 2002;9(3):151–60. [PubMed: 12380640]
9.
Kerr J.S., Mousa S.A., Slee A.M. Alpha(v)beta(3) integrin in angiogenesis and restenosis. Drug News Perspect. 2001;14(3):143–50. [PubMed: 12819820]
10.
Mousa S.A. alphav Vitronectin receptors in vascular-mediated disorders. Med Res Rev. 2003;23(2):190–9. [PubMed: 12500288]
11.
Haubner R., Wester H.J. Radiolabeled tracers for imaging of tumor angiogenesis and evaluation of anti-angiogenic therapies. Curr Pharm Des. 2004;10(13):1439–55. [PubMed: 15134568]
12.
Lee H.Y., Li Z., Chen K., Hsu A.R., Xu C., Xie J., Sun S., Chen X. PET/MRI dual-modality tumor imaging using arginine-glycine-aspartic (RGD)-conjugated radiolabeled iron oxide nanoparticles. J Nucl Med. 2008;49(8):1371–9. [PubMed: 18632815]

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