The present invention provides methods, compositions, systems, and kits comprising core-satellite nanocomposites useful for photothermal and/or MRI applications (e.g., tumor treatment and/or imaging). In certain embodiments, the core-satellite nanocomposites comprise: i) a core nanoparticle complex comprising a biocompatible coating surrounding a nanoparticle core, and ii) at least one satellite component attached to, or absorbed to, the biocompatible coating. In some embodiments, the nanoparticle core and satellite component are composed of near-infrared photothermal agent material and/or MRI contrast agent material. In further embodiments, the satellite component is additionally or alternatively composed of near-infrared optical dye material.
