Chemical synthesized nanostructures interfacing with biology

Nanomaterials with sizes comparable to cell compartments have numerous potential applications in biological and biomedical fields. In the thesis, I mainly focused on chemical synthesis of silicon nanowire (SiNW) and graphene and applying them for biological and biomedical applications. First I developed a novel nano-bio system based on functionalized SiNW to investigate the interaction between nanomaterials and cells. SiNWs were controllably synthesized via CVD process and functionalized with folate and amino groups, respectively. The strong intrinsic nonlinear optical four-wave-mixing (FWM) signals of SiNW was utilized to monitor the cellular binding and uptake of SiNWs in real time to visualize the interaction between the folate and amino group functionalized SiNWs and cells. I demonstrated that the strong and irreversible specific ligand-receptor between folate on NWs and folate receptors on CHO-β cell membranes facilitated the agglomeration of folate modified SiNWs on cells and the internalization of NWs, which was further confirmed through control experiments using normal CHO cell without folate receptors. In addition, I also observed the binding was independent of length for NWs, however, uptake of NWs highly depended on length and NWs longer than 5 μm were difficult to be internalized. In addition, for the first time, I demonstrated the use of graphene as protection film in biological environments. First, a chemical experiment was conducted to confirm graphene effectively inhibits Cu surface from corrosion, resulting in low concentration of Cu2+ ions in different biological aqueous environments. Results of cell viability tests from in vitro experiment suggested graphene coating could greatly eliminate the toxicity of Cu by inhibiting corrosion and reducing the concentration of Cu 2+ ions produced. To enhance the durability of graphene protection limited by the defects in graphene film, a new strategy was proposed by using additional thiol derivatives assembled on graphene coated Cu surface. Transferred graphene was also tested and showed reasonable protection when extra thiol coating was introduced. More importantly, for the first time, I designed and carried out a clinical standard lymphocyte transformation test to demonstrate that graphene coating inhibits metallic allergic immune response, and an in vivo experiment to show the effective protection of graphene to Cu under physiological condition. At last, a novel label-free imaging method based on transient absorption (TA) was developed for rapid visualization and quantitative layer analysis of graphene and graphene oxide (GO). TA imaging enables to visualize graphene and GO on various substrates and the intensity of TA images is linearly increasing with the layer number of graphene. More importantly, this novel method is able to image graphene with collagen coating and GO in vitro and ex vivo in real time