In vitro assessment of the dual-targeting behavior of a peptide-based magnetic resonance imaging contrast agent

In this study, a peptide-based dual-targeting magnetic resonance imaging (MRI) contrast agent (S8) was designed and synthesized. Arg-Gly-Asp (RGD) and Asn-Gly-Arg (NGR) were combined in the targeting vector so as to allow binding, on the surface of tumor cells, to integrin (v3) and aminopeptidase N (CD13), respectively. The longitudinal relaxivity (r(1)) value of S8 was 8.297 mM(-1)sec(-1) at a magnetic field of 11.7 T, which is approximately double the r(1) value (4.25 mM(-1)sec(-1)) of Magnevist, a commercially available contrast agent. MDA-MB-231 human breast cancer cells (which overexpress (v3)) and human prostate cancer cells PC-3 (which overexpress CD13) were used to investigate the tumor-targeting behavior of S8. The results from the present study indicate that the designed contrast agent, S8, targets both MDA-MB-231 and PC-3 cells.