Vertical nanopillars for highly localized fluorescence imaging

Abstract

Observing individual molecules in a complex environment by fluorescence microscopy is becoming increasingly important in biological and medical research, for which critical reduction of observation volume is required. Here, we demonstrate the use of vertically aligned silicon dioxide nanopillars to achieve below-the-diffraction-limit observation volume in vitro and inside live cells. With a diameter much smaller than the wavelength of visible light, a transparent silicon dioxide nanopillar embedded in a nontransparent substrate restricts the propagation of light and affords evanescence wave excitation along its vertical surface. This effect creates highly confined illumination volume that selectively excites fluorescence molecules in the vicinity of the nanopillar. We show that this nanopillar illumination can be used for in vitro single-molecule detection at high fluorophore concentrations. In addition, we demonstrate that vertical nanopillars interface tightly with live cells and function as highly localized light sources inside the cell. Furthermore, specific chemical modification of the nanopillar surface makes it possible to locally recruit proteins of interest and simultaneously observe their behavior within the complex, crowded environment of the cell.

Nanowire-Aperture Probe: Local Enhanced Fluorescence Detection for the Investigation of Live Cells at the Nanoscale

“…27,39−42 While both features of nanostructures have a very strong potential for future applications, they have rarely been combined to explore biological systems, with one of the few examples being the work by Xie et al with silica nanowires. 27,43,44 In this work we introduce a nanowire-aperture probe (NAP) based on GaAs nanowires. We show that when a NAP is in contact with cells, it can be exploited to study protein interactions in living cells at the nanoscale by tailoring the light through the unique photonic properties of these dielectric nanowires.…”

“…17−23 Exploring the modulation of the light pathway by nanostructures opens a window to new approaches overcoming the diffraction limitation of fluorescence-based studies, 24,25 which can be applied to address key low-affinity cellular interactions as it tackles low signal-tobackground issues in standard probing techniques. 26,27 In particular, high aspect ratio dielectric nanowires have been shown to work as photonic structures that modulate light− matter interactions through several phenomena 28−31 including guiding, 32 emitting, 33,34 and collecting light. 35,36 Out of these phenomena, the principles behind the nanowire optical waveguiding effect suggest the potential of a highly localized nanowire-based aperture (nanowire-aperture), where a subdiffraction probing volume around the nanowire is created and the radiation pattern of dipoles nearby is modified.…”

ZnO nanotube waveguide arrays on graphene films for local optical excitation on biological cells

“…To improve the spatial resolution in optical microprobing, optical probes based on nanostructures have been reported. [18][19][20][21] In these approaches, nanostructures were used as optical waveguides for illuminating a cell. The excitation volume can be highly localized near the tip of the nanostructures by optical confinement, without using additional optical components.…”

Gate bias-dependent junction characteristics of silicon nanowires suspended between polysilicon electrodes

“…One of the most promising application areas for NWs is in biological systems, which consist of a myriad of highly interactive and complex interconnections and pathways operating at various length and time scales [1]. In particular, monitoring the activities of neurons and the intercommunication among them in the brain is essential for understanding neural networks.…”

“…Nanowires (NWs) can act as electrodes in future integrated nanocircuits, as actuators, and as a model system in the study of the size effects on the intrinsic material properties [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. One of the most promising application areas for NWs is in biological systems, which consist of a myriad of highly interactive and complex interconnections and pathways operating at various length and time scales [1].…”