Nanoparticle self-assembly directed by antagonistic kinase and phosphatase activities

Superparamagnetic Fe3O4 nanoparticles (NPs) are engineered to reversibly self-assemble in response to antagonistic enzyme inputs. Tyrosine kinase activity directs substrate-NPs and SH2 domain-NPs to coalesce via polyvalent SH2- phosphopeptide binding. Phosphatase antagonizes this process and directs NP dispersion. By coupling assembly to substrate phosphorylation, the kinase activity is imaged via quantitative T2 relaxation changes in MRI.