Suppression of composite nanoparticle aggregation through steric stabilization and ligand exchange for colorimetric protein detection

Composite Fe₃O₄/Au nanoparticles are attracting considerable interest in nanomedicine due to their unique physical and chemical properties. However, successful applications of these particles are generally limited by their severe aggregation due to their ionic instability under physiological conditions. Here, by harnessing the steric stabilization and chemical ligand synergistic cooperation, we demonstrated that composite Fe ₃O₄/Au nanoparticles exhibited desirable colloidal stability, dispersity and functionalities in a wide range of pH values, rendering visual and specific detection of biomolecules of interest without using complex fluid handling and detection instruments. We envision that these novel composite nanoparticles might serve as ideal probes for real time, point of care diagnostics and therapy in resource-poor settings.