Chemical Exchange Saturation Transfer (CEST) MRI is a relatively new contrast mechanism that can be exploited for molecular imaging. This presentation will briefly review the physical chemistry of CEST MRI to demonstrate how multiple MRI contrast agents can be selectively detected during the same scan session.  To apply CEST MRI for molecular imaging, we have developed catalyCEST contrast that can detect enzyme activities.  These catalyCEST agents show a change in the chemical shift, amplitude, or chemical exchange rate after an enzyme catalyzes a covalent change in the agent's structure.  We have developed paramagnetic CEST agents that detect proteases.  We have demonstrated that a responsive catalyCEST agent and an unresponsive CEST agent can be dynamically monitored during in vivo studies of a mouse tumor model, and the comparison of the two agents can improve the detection of in vivo protease activity.  We have also developed paramagnetic CEST agents that detect an �anti-protease� which creates an amide bond.   We have also developed polymers that are triggered by enzyme activity to spontaneously disassemble into monomers that have different CEST properties, which amplifies the detection of enzyme activities.  We have also developed non-metallic, diamagnetic CEST agents that detect enzyme activities, and this presentation will compare the merits and limitations of paramagnetic and diamagnetic CEST agents for molecular imaging.  Together, these examples constitute a comprehensive overview of the emerging research field of catalyCEST MRI.

CatalyCEST MRI contrast agents that detect enzyme activities

247th National Meeting (2014)

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