A new class of biofunctional particle have emerged.
Hydrophilic polymer brush-afforded silica particles were synthesized by surface-initiated living radical polymerization, varying the diameter of silica core, the length of brush chain, and the graft density to obtain a series of samples with various structural factors. The hybrid particles were intravenously injected to mice to investigate their blood circulation and biodistribution, so that the structure factors of the hybrid particles (size, surface elasticity, etc.) strongly affect their in vivo pharmacokinetics. Some hybrid particles showed an excellently prolonged blood circulation of blood half-life more than 24h, which induced particle accumulation in tumor tissues due to the so-called EPR effect. Various types of nanoparticles can be modified by the similar method, and more complex architectures can also be provided in the brush layer such as drug-holding or bioactive sites. Thanks to its versatility and robustness, this technique may create functional particles applicable to many biomedical fields such as DDS, bioimaging, immunodiagnosis, separation or purification.