Janus nanoparticles with decyls on one side direct extended cell membrane anchoring

One-side functionalization of nanoparticles can produce Janus structures with unique physical properties that direct differential interaction with biological interfaces compared with conventional nanoparticles. Here, we show that the functionalization of hydrophobic molecules on one side of the nanoparticle surface enhances the particle-particle interactions that decrease their colloidal stability in water but direct extended anchoring with the cell membrane. In particular, we synthesized 50-60 nm colloidal silica that comprises a porous silica core doped with gold/iron oxide nanoparticles and terminated with hydrophilic dextran groups on one side and with hydrophobic decyl groups on the other side. We show that this Janus structure induces nanoparticle-nanoparticle interactions via decyl groups that decrease their colloidal stability and drive attachment to the lipophilic cell membrane. A comparative study shows that these Janus nanoparticles can label the cell membrane faster than their respective symmetric nanoparticles and remain at the cell membrane for a longer time. These Janus nanoparticles can be used for magnetic cell separation without cytotoxicity and for drug delivery without the entry of the nanocarrier into the cell.