Simultaneous in vivo imaging of dual targets of tumor : detection and quantification with dual nano probes and computed tomography

Abstract

Background

Use of multiple target-specific agents to determine disease markers and eventually make a correct diagnosis has been a standard practice in clinical medicine. We aimed to investigate the feasibility of simultaneous in vivo imaging of dual tumor targets by micro-CT imaging.

Materials and Methods

Gold nanoparticles (AuNp, 30 nm) were coated with polyethylene glycol and conjugated with anti-human epidermal growth factor receptor (HER2/neu) aptamers. Liposomes containing iodine (Lipo-I) with or without conjugation with vascular endothelial growth factor-2 (VEGFR2) aptamers were prepared. A female BALB/c-nude mouse xenograft tumor model that highly expresses the HER2/neu cancer markers was generated. Animals were divided into six groups according to the combination of contrast agents (n=3 for each group). After intravenous injection of the nanoparticle contrast agents, CT density was measured within the tumor and compared between subgroups with different kinds of contrast injection. CT-derived contrast enhancements were compared with histologic analysis by hematoxylin and eosin (H&E) and immunohistochemical (IHC) staining.

Results

The contrast enhancement of tumor was greater in the HER2-aptamer conjugated gold nanoparticle (HER2-Apt-AuNp) group than in the AuNp group immediately (39.4 vs. 7 HU), 24 hours (138.1 vs. 116.6 HU), and 48 hours (186.0 vs. 162.4 HU) after contrast administration. The Herceptin block + HER2-Apt-AuNp group showed less enhancement (129.2 HU after 48 hours) than the HER2-Apt-AuNp group and AuNp group. The VEGFR2-conjugated liposomal iodine (VEGFR-Apt-Lipo-I) group demonstrated greater enhancement than the Lipo-I group after contrast administration (65.4 vs. 51.8 HU immediately after contrast administration). The combination of VEGFR-Apt-Lipo-I and HER2-Apt-AuNp showed greater contrast enhancement than the HER2-Apt-AuNp at 24 hours (187.4 vs. 138.1 HU) and 48 hours (208.5 vs. 186 HU), respectively. IHC staining revealed that the contrast enhancement area by AuNp and Lipo-I was largely consistent with the HER2-postive and VEGFR2-positive area, respectively.

Conclusion

Micro-CT can be applied for simultaneous in vivo imaging of dual tumor targets.