Dorit Granot1, Erik M. Shapiro1,2
1Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, CT, United States; 2Department of Biomedical Engineering, Yale University, New Haven, CT, United States
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.