Non-invasive pH and temperature mapping is needed for cancer research because these parameters are exploited in tumor diagnosis or therapy. To that goal, smart contrast agents (SCAs) composed of paramagnetic lanthanide ion (Ln3+) with derivatives of 1,4,7,10 tetraazacyclododecane (cyclen) have been developed for MR. We have shown that two commercial Tm3+-based SCAs, TmDOTP5 and TmDOTMA, provide extracellular pH/temperature maps with biosensor imaging of redundant deviation in shifts (BIRDS). These types of SCAs are used as MRS shift agents to separate resonances of endogenous molecules (or ions). However BIRDS maps the 1H signals from non-exchangeable protons (i.e., CHx) of the SCA itself, which is in contrast to the paramagnetic chemical exchange saturation transfer (PARACEST) agent that features exchangeable protons (e.g., OH or NHx). Detection of the non-exchangeable protons by BIRDS provides redundancy to extract temperature/pH, the chemical shift imaging (CSI) data are acquired rapidly for superior signal-to-noise ratio (SNR), and quantification is nearly insensitive to the magnetic field strength (Bo), poor Bo shim conditions, and the SCA's concentration. BIRDS with high speed 2D CSI at 11.7T allows spatial resolution of ~10 Novel paramagnetic lanthanide macrocyclics will be synthesized and translated for tumor imaging in rat brain. Agents will feature non-exchangeable protons, detectable by biosensor imaging of redundant deviation in shifts (BIRDS), for pH and temperature mapping, where quantification is independent of agent concentration and magnetic field. Each agent, designed for superior sensitivity of BIRDS, will undergo assays for kinetic inertness, brain access, cytotoxicity, and distribution. Results will identify structural features with toxicology and biodistribution suitable for future pre-clinical studies.Public Health Relevance
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