MAGNETOTATIC BACTERIA MRI POSITIVE CONTRACT ENHANCEMENT AGENT AND METHODS OF USE

摘要

Magnetic resonance imaging (MRI) is enhanced by contrast agents such as superparamagnetic iron-oxide (SPIO) particles that resemble magnetite particles produced by magnetotactic bacteria. Magnetospirillum magneticum AMB-1 produces positive MRI contrast when generating ultrasmall magnetite particles (10-40 nm diameter). Positive MRI contrast permits clearer distinction from image voids compared to negative contrast. T1-weighted MRI showed that such bacteria increased positive contrast 2.2-fold (p0.02) in vitro and 2.0-fold (p0.02) following intratumoral injection in mouse tumor xenografts. Upon intravenous delivery, Magnetospirillum magneticum AMB-1 targeted tumors and generated increased positive MRI contrast in them (1.4-fold; p0.01). AMB-1 tumor targeting was shown by viable counts, microPET imaging of radio-labeled AMB-1, and Prussian blue staining of tumor sections. Thus, magnetotactic bacteria provide a tool for improving cancer diagnosis and monitoring treatment response by MRI.