19F MRI is valuable for in vivo imaging due to the only trace amounts of fluorine in biological systems. Because of the low sensitivity of MRI however, designing new fluorochemicals remains a significant challenge for achieving sufficient 19F signal. Here, we describe a new class of high-signal, water-soluble fluorochemicals as 19F MRI imaging agents. A polyamide backbone is used for tuning the proteolytic stability to avoid retention within the body, which is a limitation of current state-of-the-art perfluorochemicals. We show that unstructured peptides containing alternating N-ε-trifluoroacetyllysine and lysine provide a degenerate 19F NMR signal. 19F MRI phantom images provide sufficient contrast at micromolar concentrations, showing promise for eventual clinical applications. Finally, the degenerate high signal characteristics were retained when conjugated to a large protein, indicating potential for in vivo targeting applications, including molecular imaging and cell tracking.

19 FM RI is valuable for in vivo imaging due to the only trace amounts of fluorine in biological systems.B ecause of the low sensitivity of MRI however,d esigning new fluorochemicals remains as ignificant challenge for achieving sufficient 19 Fs ignal. Here,w ed escribe an ew class of highsignal, water-soluble fluorochemicals as 19 FM RI imaging agents.Ap olyamide backbone is used for tuning the proteolytic stability to avoid retention within the body,w hichi s al imitation of current state-of-the-art perfluorochemicals.W e show that unstructured peptides containing alternating N-etrifluoroacetyllysine and lysine provide adegenerate 19 FNMR signal. 19 FMRI phantom images providesufficient contrast at micromolar concentrations,s howing promise for eventual clinical applications.F inally,t he degenerate high signal characteristics were retained when conjugated to al arge protein, indicating potential for in vivo targeting applications, including molecular imaging and cell tracking.