(19)F MRI monitoring of gene expression in living cells through cell-surface β-lactamase activity.

Magnetic resonance imaging provides important intravital information on deep tissues that cannot be visualized by other methods. Although we had previously developed an off/on switching (19)F MRI probe to monitor reporter enzyme activity on the basis of the paramagnetic relaxation enhancement effect, it was difficult to monitor biological events in living cells because the (19)F MRI probe did not permeate living cell membrane. In this study, we have developed a new (19)F MRI system for monitoring gene expression in living cells by exploiting cell-surface-displayed β-lactamase and the specifically designed (19)F MRI probe. By using this system, cellular gene expression was successfully detected by (19)F MRI without cell fixation. This imaging strategy shows promise for monitoring in vivo gene expression, and therefore it could lead to useful technologies for the diagnosis and therapy of various diseases.