Vertical silicon nanowires as a universal platform for delivering biomolecules into living cells

Abstract

A generalized platform for introducing a diverse range of biomolecules into living cells in high-throughput could transform how complex cellular processes are probed and analyzed. Here, we demonstrate spatially localized, efficient, and universal delivery of biomolecules into immortalized and primary mammalian cells using surface-modified vertical silicon nanowires. The method relies on the ability of the silicon nanowires to penetrate a cell's membrane and subsequently release surface-bound molecules directly into the cell's cytosol, thus allowing highly efficient delivery of biomolecules without chemical modification or viral packaging. This modality enables one to assess the phenotypic consequences of introducing a broad range of biological effectors (DNAs, RNAs, peptides, proteins, and small molecules) into almost any cell type. We show that this platform can be used to guide neuronal progenitor growth with small molecules, knock down transcript levels by delivering siRNAs, inhibit apoptosis using peptides, and introduce targeted proteins to specific organelles. We further demonstrate codelivery of siRNAs and proteins on a single substrate in a microarray format, highlighting this technology's potential as a robust, monolithic platform for high-throughput, miniaturized bioassays. intracellular delivery | microarray | high-throughput bioassay | nanobiotechnology

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.…”

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.…”

“…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.…”

Vertical nanopillars for highly localized fluorescence imaging

“…In 2007, an intriguing study by Kim et al reported that vertical silicon nanowires penetrated living mammalian cells that grew attached to the substrate without affecting the cell viability in the long term (8). Recently, Shalek et al reported the use of vertical silicon nanowires to deliver biomolecules such as proteins and DNA plasmids into living cells that grew attached to the nanowires (9). Together with other works that show vertical nanowires can support cell culture (10)(11)(12)(13)(14), these observations suggest a new and exciting possibility of using vertical nanowires as a universal platform to probe intracellular molecular events.…”