The presently disclosed subject matter provides hybrid nanomaterials for use as magnetic resonance imaging (MRI), optical and/or multimodal contrast imaging agents. The hybrid nanomaterials comprise a polymeric matrix material and a plurality of coordination complexes, each coordination complex comprising a functionalized chelating group and a paramagnetic metal ion. The nanoparticle can further comprise a luminophore. Methods of synthesizing and using the nanoparticles are provided. The nanoparticles can be used to diagnose diseases, including cancer, cardiovascular disease, and diseases related to inflammation.