Nanoparticles that facilitate imaging of biological tissue and methods for formulating the nanoparticles are provided. In order to form suitable nanoparticles for imaging, an anionic surfactant may be applied to superparamagnetic nanoparticles to form modified nanoparticles. The modified nanoparticles may be mixed with a polymer in a solvent to form a first mixture, and a non-solvent may be mixed with the first mixture to form a second mixture. An emulsion may be formed from the second mixture and the polymeric nanoparticles may be isolated from the emulsion. In certain embodiments of the invention, an antibody may be attached to the polymeric nanoparticles to facilitate attachment of the nanoparticles to biological tissue.