Cellular binding and internalization of functionalized silicon nanowires

Nanostructures with precise control of sizes and shapes, intrinsic read-out signals for tracking, and flexible surface chemistry for bioconjugation can offer an excellent system to study interaction between nanomaterials and cells. In this paper, a new nanobio system based on functionalized silicon nanowires (SiNWs) was developed. Using the intensive and intrinsic nonlinear optical signal of SiNWs, we visualized the interaction between the folate and amine group functionalized SiNWs and cells by monitoring the cellular binding and uptake of SiNWs in real time. We demonstrated that the strong specific ligand-receptor interaction between folate on NWs and folate receptors on CHO-β cell membranes expedited agglomeration of folate modified SiNWs on cells and internalization of NWs. Such specific targeting was further confirmed through control experiments done with normal CHO cell without folate receptors. Weaker nonspecific charge-charge attraction led to longer time required for amino group modified SiNWs to be bound on cell membrane. No effective accumulation was noticed for unmodified SiNW with native oxidized surface layer. In addition, we also observed the binding was independent of length for NWs ranging between 2.5 and 8.0 μm. Uptake of NWs highly depended on length and NWs longer than 5 μm were difficult to be internalized. Our results provided an insight of cellular interaction with 1-dimensional nanomaterials.