Preparation and in vitro studies of MRI-specific superparamagnetic iron oxide antiGPC3 probe for hepatocellular carcinoma

Youwei Li,^1,2 Zhengguang Chen,³ Fei Li,¹ Jichen Wang,⁴ Zongming Zhang<sup>1,5

1</sup>School of Medicine, Tsinghua University, ²Department of Radiology, Beijing Chuiyangliu Hospital, ³Department of Radiology, Dongzhimen Hospital Affiliated to Beijing University of Chinese Medicine, Beijing; ⁴Department of Radiology, Nanjing BenQ Hospital, Nanjing, ⁵Department of Hepatobiliary Surgery, Futian Hospital, Guangdong Medical College, Shenzhen, People's Republic of China

Background: The aim of this study was to develop an antiGPC3-ultrasuperparamagnetic iron oxide (USPIO) probe for early detection of hepatocellular carcinoma.
Methods: GPC3 and AFP receptors were selected as biomarkers and conjugated with USPIO nanoparticles coated by dextran with carboxylate groups to synthesize antiGPC3-USPIO and antiAFP-USPIO probes. HepG2 cells (a human hepatocellular carcinoma cell model with high expression of GPC3) were used along with SMMC-7721 cells (a hepatocellular carcinoma cell model with no expression of GPC3), HeLa cells (a cervical cancer model), and HL-7702 (normal hepatocytes) which were used as controls. After incubation with the probes, the iron content in the cells was calculated, USPIO nanoparticles in cells were observed using transmission electron microscopy, and T1 and T2 relaxation times were measured with a 1.5 T magnetic resonance scanner.
Results: AntiGPC3-USPIO probes with a mean hydrodynamic diameter of 47 nm showed good biological compatibility. Transmission electron microscopic images indicated that the amount of USPIO nanoparticles taken up was significantly higher in HepG2 cells incubated with antiGPC3-USPIO than that in HepG2 cells incubated with antiAFP-USPIO or USPIO nanoparticles and that in the SMMC-7721 or HeLa cells incubated with antiGPC3-USPIO probes, antiAFP-USPIO probes, or USPIO nanoparticles. The higher the concentration and the longer the incubation time, the greater the number of USPIO nanoparticles found in the cells. No USPIO nanoparticles were found in the HL-7702 cells. All of the HepG2, SMMC-7721, and HeLa cells incubated with antiGPC3-USPIO, antiAFP-USPIO, or USPIO nanoparticles were able to shorten the T1 and T2 values in agar solution, especially the T2 images of HepG2 cells incubated with antiGPC3-USPIO probes.
Conclusion: AntiGPC3-USPIO probes can be utilized as a specific magnetic resonance targeting contrast agent for early detection of hepatocellular carcinoma. Using a 1.5 T magnetic resonance scanner, the optimal time for imaging HepG2 cells was around 2–4 hours after incubation with antiGPC3-USPIO probes.

Keywords: magnetic resonance imaging, hepatocellular carcinoma, HepG2 cells, superparamagnetic iron oxide antiGPC3-USPIO probe