Visualization through magnetic resonance imaging of DNA internalized following "in vivo" electroporation.

The ability to visualize plasmid DNA entrapment in muscle cells undergoing an "in vivo" electroporation treatment was investigated on BALB/c mice using a 7-T magnetic resonance imaging (MRI) scanner using the paramagnetic Gd-DOTA-spd complex as imaging reporter. Gd-DOTA-spd bears a tripositively charged spermidine residue that yields a strong binding affinity toward the negatively charged DNA chain (6.4 kb, K(a) = 2.2 x 10(3) M(-1) for approximately 2500 +/- 500 binding sites). Cellular colocalization of Gd-DOTA-spd and plasmid DNA has been validated by histological analysis of excised treated muscle. In vivo MRI visualization of Gd-DOTA-spd distribution provides an excellent route to access the cellular entrapment of plasmid DNA upon applying an electroporation pulse.