In Vivo Implementation of REACTION (Release Activation of Iron Oxide Nanoparticles)

Dorit Granot¹, Erik M. Shapiro^1,2

Here we describe a new enzyme/contrast agent paradigm which can achieve enzymatically responsive changes in cellular T2 and T2*. Cells are labeled with particles coated with a biopolymer that restricts the approach of water to the particle, preventing the magnetic core from relaxing protons. Cleavage of the coat by a specific enzyme reveals the magnetic center thus increasing the relaxivity of the agent. In an in vivo demonstration of this paradigm, large enhancements of dark contrast volume and CNR within the contrast regions were measured, for injected cells co-labeled with enzyme and particles versus cells labeled with particles alone.