1H-NMR relaxometric studies of interaction between apoptosis specific MRI paramagnetic contrast agents and micellar models of apoptotic

1H-NMR was previously used to analyze the interaction between peptides (E3 and R826) selected by phage display to target apoptotic cells and phospholipidic models of these cells. In order to avoid the use of apoptotic cells and to get a fast evaluation of the efficiency of the potential MRI contrast agents obtained by grafting these peptides and their scramble analogs on a paramagnetic gadolinium complex, their proton relaxometric behavior was investigated in presence of micelles mimicking healthy and apoptotic cells. Their preferential interaction with 1,2-dipalmitoyl-sn-glycero-3-phospho-L-serine [DPPS] micelles mimicking apoptotic cells as compared to 1,2-dipalmitoyl-sn-glycero-3-phosphocholine [DPPC] micelles modeling healthy cells was shown by nuclear magnetic relaxation dispersion (NMRD) profiles and the enhancement of the transverse proton relaxation rates at 60 MHz. The association constant values confirm the stronger interaction of the selected conjugated peptides (Ka Gd-PMN-E3: 2.43E4 M-1; Ka Gd-DTPA-R826: 2.91E4 M-1) as compared to their conjugated scrambles (Ka Gd-PMN-E3sc: 0.18E4 M-1; Ka Gd-DTPA-R826sc: 0.32E4 M-1) even if the conjugation of E3 and R826 seems to decrease their interaction.