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. Author manuscript; available in PMC: 2009 Feb 18.
Published in final edited form as: Mol Imaging. 2007 May–Jun;6(3):156–170.

Figure 1.

Figure 1

A, Description of the oligo nucleic acid–based superparamagnetic iron oxide nanoparticle (SPION) probe. Linkage of SPION and single-stranded phosphorothioate-modified oligodeoxynucleotides is based on the avidin-biotin interaction. B, Cartoon depicting how living cells with normal cfos messenger ribonucleic acid (mRNA) transcription are able to retain SPION-cfos probe by complex formation based on complementary base pairing between the probe and the intracellular mRNA target. The presence of T2* magnetic resonance contrast agent (SPION) can cause localized magnetic resonance signal reduction owing to cells that contain SPION. On the other hand, dead cells damaged by apoptosis exhibit fragmented deoxyribonucleic acid (DNA), and no new cfos mRNA can be transcribed owing to a lack of available DNA template. As a result, there is less or no uptake of SPION-cfos by the dead cell.