Magnetic optical sensor particles with multifuncation cores and shells are synthesized via a facile nanoprecipitation method and the subsequent modification of the particle shell. The hydrophobic particle core includes optical oxygen indicators, a light harvesting system, photosensitizers, and magnetic nanoparticles. Further functionalities are ntroduced by modifying the shell with enzymes, antibodies, multiple layers of polyelectrolytes, stimuli-responsive polymers, and luminescent indicator dyes. The hydrodynamic diameter is tunable by varying different precipitation parameters.