Ultrasmall Rigid Particles as Multimodal Probes for Medical Applications

Ultrasmall but multifunctional: Rigid imaging particles that are smaller than 5 nm in size can be obtained in a top‐down process starting from a core–shell structure (core=gadolinium oxide; shell=polysiloxane). They represent the first multifunctional silica‐based particles that are sufficiently small to escape hepatic clearance and enable animal imaging by four complementary techniques.