Gadolinium-labeled magnetite nanoparticles (GMNPs) were synthesized via a bioinspired manner 10 use as dual contrast agents for T-1- and T-2-weighted magnetic resonance imaging. A mussel-derived adhesive moiety, 3,4-dihydroxy-L-phenylalanine (DOPA), was utilized as a robust anchor to form a mixed layer of poly(ethylene glycol) (PEG) chains and dopamine molecules on the surface of iron oxide nanoparticlcs. Gadolinium ions were subsequently complexed at the distal end of the dopamine molecules that were prefunctionalized with a chelating ligand for gadolinium. The resultant GMNPs exhibited high dispersion stability in aqueous Solution. Crystal structure and superparamagnetic properties of magnetite nanocrystals were also maintained after the complexation of g a pits for T-1 and T-2-weighted magnetic resonance imaging was demonstrated by conducting in vitro and in vivo imaging and relaxivity measurements.