A New R2/R1 Ratiometric Method to Measure PH with a Dendrimer-Based PH-Responsive MRI Contrast Agent

Meser M. Ali¹, Parvez Ismail Bhuiyan¹, Hassan Bagher-Ebadian^2,3, Branislava Janic¹, Robert a knight^2,3, James R. Ewing^2,3, Ali Syed Arbab¹

We have recently developed a new pH-responsive dendrimer-based MRI contrast agent with excellent improvements in both overall sensitivity and responsiveness of relaxivities to pH. Therefore, the R2/R1 ratio of this dendritic MR agent has been used to measure pH and the ratio (r2/r1) showed pH-response. This pH measurement is independent of the absolute concentration of the agent so that a single MRI agent can measure pH without requiring a second MRI to account for pharmacokinetics.