Scheme 1.

(A) Rational design of self-assembling, dual-modality molecular probes containing four essential elements: a hydrophobic domain to promote self-assembly in aqueous environments, a fluorophore for optical imaging, a chelator to enable complexation with metals, such as gadolinium (Gd) for MR contrast, and a hydrophilic headgroup. These amphiphilic molecules are designed to self-assemble into spherical nanoparticles. (B) Chemical structures of the two probes used in the study: [Gd(III)]-1 and [Gd(III)]-2.