Investigation Of The Interaction Of Gold Nanoparticles And Cells By Dark-field Microscopy

Gold Nanoparticles have fascinated scientists for recent years and been widelyapplied as gene-regulating agents, imaging agents, drug deliver and photoresponsivetherapeutics. Due to localized surface plasmon resonance (LSPR)，Gold nanoparticlesbrightly scatter under dark-field illumination and their scattering intensity depends ontheir size, shape and surrounding environment. Moreover, the plasmon coupling ofgold nanoparticles, which are moving toward to each other, lead to visible red shiftingand apparent intensity enhancing. Meanwhile, increasing the number of goldnanoparticles in clusters also results in its spectral red shifting and producing abrighter dot in dark-field microscope. The unique behavior of AuNPs provides us aperspective way to investigate the congregation and fate of intracellular nanoparticles.First, to reveal the relationship between the associated scattering cross sectionand the numbers of AuNPs in clusters, we co-localized the gold nanoparticles withSEM and Dark-Field microscopy and simulated the spectral of gold nanoparticleswith FDTD solution. Therefore, we set up a noval method to estimate the aggregationlevel of gold nanoparticle cluster through Dark-Field microscopy.Moreover, we combined fluorescence microscopy with DFM to estimate thesub-cellular location of nanoparticles and the internalization process of intracellarAuNPs with cells, including adhesion on the membrane, motion along themicrotubules. We found that gold nanoparticle moves rapidly along aclathrin-dependent pathway during the procees of endocytosis. The internalizatiedgold nanoparticles move through a microtubules-dependent pathway from earlyendosome to late endosome and are finally transported into lysosome. During his process, gold nanoparticles assemble into clusters step by step (monomer, smallaggregation, large aggregation). Furthermore, by tracking single particle, we foundthat single gold nanoparticle (green spot in dark-field image) and its small aggregationmove quickly, while the larger aggregation of gold nanoparticles moves in a limitarea.Furthermore, gold nanoparticles move along tubulin in different patterns:majority of them statics in certain area during observation. While most of movinggold nanoparticles move in a minus end net direction, the rest of them movebi-directions. Moreover, some nanoparticles keep moving in initial directions aftercolliding each other. More importantlyt, some small aggregations thermself mergeinto larger aggregations. These different motive patterns are correction with motorproteins.Finally, to estimate how the aggregation degree and conformation of goldnanoparticles influnence their interaction with cells, with the help of DNAnanotechnology, we engineer different gold nanoparticle aggregations with certainnumber. Interestingly, we found that this aggregation of gold nanoparticlessignificantly enhances the uptake efficiency of cell.