Biotin-decorated fluorescent silica nanoparticles with aggregation-induced emission characteristics: fabrication, cytotoxicity and biological applications.

Biotin-decorated fluorescent silica nanoparticles (FSNPs) were successfully fabricated by a sol-gel reaction of silole-functionalized siloxane followed by a sequential reaction with tetraethoxysilane, (3-aminopropyl)triethoxysilane and biotin. The FSNPs were uniformly sized, spherical in shape and monodispersed. While their silole precursor was non-emissive in solution, the suspension of the FSNPs emitted strong green light upon photoexcitation due to the aggregation-induced emission characteristics of the silole aggregates in the hybrid nanoparticles. Morphology study and cell viability, trypan blue exclusion, Annexin V-FITC/PI apoptosis and ROS generation assays showed that the FSNPs showed low toxicity to living cells. The FSNPs worked as fluorescent visualizers for selective imaging of the cytoplasm of tumor cells with over-expressed biotin receptors. The fluorescent nanoparticles were lastingly retained inside the living cells, thus enabling long-term tumor cell tracking over multiple passages and quantitative analysis of tumor cell migration.