Monodisperse magnetic nanoparticles conjugated with virus-surface-specific antibodies self-assemble in the presence of specific viral particles to create supramolecular structures with enhanced magnetic properties, as detected by magnetic resonance methods (NMR/MRI). The observed magnetic relaxation changes that occur upon viral-induced assembly allowed for highly sensitive and selective detection of a virus in complex biological media. The developed method was shown to specifically detect adenovirus-5 and herpes simplex virus-1 at concentrations of 5 viral particles/10 muL without the need of extensive sample preparation. The applications of this new method span from high-throughput NMR detection of viruses in biological samples to potential MR imaging of viral distribution in vivo.

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Monodisperse magnetic nanoparticles conjugated with complementary oligonucleotide sequences self-assemble into stable magnetic nanoassemblies resulting in a decrease of the spin-spin relaxation times (T2) of neighboring water protons. When these nanoassemblies are treated with a DNA cleaving agent, the nanoparticles become dispersed, switching the T2 of the solution back to original values. These qualities render the developed nanoparticles and their nanoassemblies as magnetic relaxation switches capable of screening for DNA-cleaving compounds by magnetic resonance methods such as MRI and NMR.