Recent efforts have shown that nanoscale materials, specifically, metal-based nanoparticles, hold particular promise for the development of multifunctional imaging probes. These new materials provide the means to chaperone and concentrate both drugs and contrast agents in specific organs, tissues, and cells. Therefore, we have prepared a Gd(III)-modified DNA-TiO2 semiconducting nanoparticle that is detectable in cells by MR imaging. These labeled particles are retained at specific subcellular locations via DNA hybridization to intracellular targets, hence creating the first nanoparticle system capable of targeting specific DNA sequences while being simultaneously detected via MR imaging.