In biological research, the conjugation of interesting proteins or antibodies with various molecular labels is quite frequent. These conjugations, in particular, have made it much easier to find labeled proteins, their binding partners, or antigens in the case of labeled antibodies. Recently, multifunctional particles have been created for a variety of biological applications, including drug delivery, cellular and molecular detection, and biomolecule separation. These particles include colloidal gold, nanoparticles, and magnetic particles. Additionally, particles—and particularly nanoparticles—are widely used in multiplexing biomolecule assays, such as agglutination tests and assays, particle capture ELISA procedures, polymerase chain reaction (PCR) tests, assays based on superparamagnetic materials, and as fluorescent labels or stains for detecting biological molecules.