MR molecular imaging of HER-2 in a murine tumor xenograft by SPIO labeling of anti-HER-2 affibody.

In vivo molecular imaging is a rapidly growing research area both for basic and clinical science. Non-invasive imaging of in vivo conditions at the molecular level increases understanding of the biological characteristics of normal and diseased tissues without the need for invasive surgical procedures. Among the various imaging modalities, magnetic resonance imaging (MRI) has garnered interest as a molecular imaging modality due to its high spatial resolution. Here, we have demonstrated that the combined use of HER-2 targeting affibody, a small 7 kDa molecule that behaves similarly to antibodies, and superparamagnetic iron oxide (SPIO) can non-invasively image HER-2 expressing cells or tissues both in vitro and in vivo by MRI. This preliminary study demonstrates that affibody-SPIO is a feasible, target-specific contrast agent for in vivo MR molecular imaging.