Interfacing Silicon Nanowires with Mammalian Cells

Abstract

Nanotechnology has received increased attention in the biological research field. The important examples are (1) the usage of nanoparticles in optical and magnetic resonance imaging; 1,2 (2) the demonstration of potential application of metal nanoshells and carbon nanotubes for the treatment of tumor and cancer cells; 3,4 and (3) the application of nanowire-based transistors to electrically detect specific biomolecules. 5,6 In all of these cases, the nanomaterials are functioning either inside the cells or at the vicinity of the surface of biomolecules. Direct interconnection of the cells to the external world by interfacing nanomaterials may afford great opportunities to probe and manipulate biological processes occurring inside the cells, across the membranes, and between neighboring cells. 7,8 A nanoscale material with high aspect ratio is a good candidate for this application. For instance, silicon nanowires (SiNWs, d ) 1-100 nm) are a few orders of magnitude smaller in diameter than mammalian cells (d cell ∼ on the order of 10 µm) yet comparable to the sizes of various intracellular biomolecules. The nanowires have high aspect ratio (<10 3 ) and yet are sufficiently rigid to be mechanically manipulated. The nanometer scale diameter and the high aspect ratio of SiNWs make them readily accessible to the interiors of living cells, which may facilitate the study of the complex regulatory and signaling patterns at the molecular level.In this Communication, we present the first demonstration of a direct interface of silicon nanowires with mammalian cells such as mouse embryonic stem (mES) cells and human embryonic kidney (HEK 293T) cells without any external force. The cells were cultured on a silicon (Si) substrate with a vertically aligned SiNW array on it. The penetration of the SiNW array into individual cells naturally occurred during the cell incubation. The cells survived up to several days on the nanowire substrates. The longevity of the cells was highly dependent on the diameter of SiNWs. Furthermore, successful maintenance of cardiac myocytes derived from mES cells on the wire array substrates was observed, and gene delivery using the SiNW array was demonstrated.SiNWs were synthesized vertically aligned with respect to Si-(111) substrates via chemical vapor deposition as described earlier. 9 The diameter of the nanowires was controlled by the size of gold nanoparticles that were used as catalytic seeds for the nanowire synthesis or by reducing the diameter of Si nanowires via oxidation and subsequent hydrofluoric (HF) acid etching step. 10 The SiNW substrates had a native oxide layer and were used without any surface modification unless otherwise specified. Before any exposure to living cells, the substrates were sterilized in a solvent of 70% ethanol and 30% sterile water.First, physical interaction between the nanowires and the cells was studied using confocal microscopy and scanning electron microscopy (SEM). Mouse embryonic stem cells stably expressing green fluorescent protein (GFP) were cultured o...

Deflection induced cellular focal adhesion and anisotropic growth on vertically aligned silicon nanowires with differing elasticity

“…Cells cultured on SiNW substrates could also adhere regardless of the diameter of the nanowire used, and their high density prevented them from being pierced by the SiNWs (Figures 2b and c). 26,27 When cells adhered to the SiNWs-10 substrate, they rounded up extensively and exhibited a radial alignment (Figure 2b), whereas those on a SiNWs-01 substrate displayed an anisotropic morphology ( Figure 2c). As they were associated with different degrees of spreading, the morphologies of the adhered cells had a significant influence on the cell area (N = 72 cells), as shown in Figure 2g.…”

Spatially, Temporally, and Quantitatively Controlled Delivery of Broad Range of Molecules into Selected Cells through Plasmonic Nanotubes

“…However, microinjection is diffi cult to automate, and electroporation presents some concerns related to potential damage. Some diffi culties can be partially overcome by culturing cells in adhesion with arrays of alumina nanostraws [ 8 ] or vertical silicon nanowires [ 9,10 ] which represent advanced versions of electroporation and microinjection, respectively.…”

Nanosheet transfection: effective transfer of naked DNA on silica glass

“…7 Nanowires that can pierce into cells are rather cytotoxic and not as effective in the naked DNA delivery. 8,9 The high cell survival rate on our silica upright nanosheets suggests that the nanosheets may not penetrate the cell membrane, which is similar to the case of nanopillars. 24 Regarding the size of the nanosheet features (thickness and depth), we could control the procedures, such as the etching time, to obtain nanosheets with different geometric parameters, for example, those with a wall thickness of 5-400 nm and a height of 50-1100 nm.…”

“…A few other mechanisms have been proposed to increase transfection in the literature, such as passive delivery by concentration difference, 33 direct penetration of nanowires 8,9 and mechanical stimulation by microfluidics, which creates transient holes on the cell membrane that enable the diffusion of biomolecules into the cells. 34 Unlike these previous approaches, the plasmids in our study were not packaged or pre-adsorbed on a material surface before cell seeding.…”

“…7 Meanwhile, silicon nanowires can pierce through the cell membrane and promote the transfection of plasmid DNA/transfection reagent complexes that are tethered on the nanowires. 8 Coating the nanowires with aminosilane further improves the gene and protein delivery. 9 In the existing technologies that involve either forward or reverse transfection, the efficiency of transfecting naked plasmid DNA without physically penetrating a cell remains notably low.…”