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

Yi-Seul Park,Seo Young Yoon,Jeong Su Park,Jin Seok Lee

doi:10.1038/am.2016.5

Abstract

Cellular adhesion and growth on substrates with differing surface topography are known to induce unusual cell behaviors. Here, we investigated the adhesion and growth of human embryonic kidney 293T cells on vertically aligned silicon nanowires. Varying the diameter of nanowires affected their elasticity, which in turn caused variations in cell morphology and adhesion. Calculation of their elastic modulus revealed that long and thin nanowires are easier to deflect and thus provide more focal adhesion sites for adherent cells. And, induced mechanical tension triggered cellular anisotropic growth in the direction of tension, creating a greater rate of filopodium growth than was observed with a bare glass substrate devoid of mechanical tension. This nanotopographical approach provides important insights into the role of artificial substrates in the modulation of cell behavior and a conceptual framework for further analysis of substrate-induced changes in cellular activity. The elasticity of silicon nanowires is found to affect the shape and adhesion of embryonic kidney cells grown on the nanowires. The surface topography and mechanical properties of supports used to grow stem cells are known to affect cell behaviour. Now, Jin Seok Lee and co-workers at Sookmyung Women's University in Seoul, Korea, have shown that long, slender silicon nanowires that are easier to deflect provide more adhesion sites for human embryonic kidney cells than stiffer nanowires. They also found that the application of mechanical tension to the nanowires induced cells to grow along the direction of tension, giving higher growth rates than on tension-free surfaces. These findings provide important insights for guiding future studies of substrate properties used to control cell adhesion and growth. The cell adhesion and growth were studied on vertically aligned silicon nanowires with different diameter. Varying the diameter of nanowires affected their elasticity, resulting in a difference in cell morphology and adhesion. The formation of focal adhesion and anisotropic cell growth was promoted on thin silicon nanowires. Fluorescence analysis demonstrated that the cytoskeletal actin dynamics was affected by the mechanical tension of elastic nanotopography.

Highlights

In recent years, a significant amount of research has focused on the biophysical cues provided by extracellular matrices that regulate cell phenotype and function.[1,2,3] In particular, surface topography has been shown to modulate cell adhesion, growth, proliferation and differentiation by altering intracellular signal transduction and gene expression.[4,5] Nanostructured materials with various morphologies have received much attention over the past few decades in the field of biological research, owing to advances in nanotechnology that have enabled precision controlled nanofabrication
We investigated the effect of different density between silicon nanowires (SiNWs)-10 and SiNW-01 substrates and the morphology of cells grown on high density of SiNWs-10 substrate and low density of SiNWs-01 substrate[22] compared with Figures 2b and c, respectively
The nanotopography of the substrate influenced the distribution of focal adhesion, which is either continuous or discrete, and this subsequently influenced cell adhesion and morphology

Summary

Introduction

A significant amount of research has focused on the biophysical cues provided by extracellular matrices that regulate cell phenotype and function.[1,2,3] In particular, surface topography has been shown to modulate cell adhesion, growth, proliferation and differentiation by altering intracellular signal transduction and gene expression.[4,5] Nanostructured materials with various morphologies have received much attention over the past few decades in the field of biological research, owing to advances in nanotechnology that have enabled precision controlled nanofabrication. Modulation of cell adhesion and growth using various topographical cues is well studied, most published data address or exploit the topographical confinement that is imposed by the nanostructured architecture.[8,9] In other words, overall control of cellular response is performed by cell isolation in the structure through geometry, and is not influenced by surface topography. It is essential for surface topography to be studied through controlling the shape, size and density of the nanostructure. The accelerated development of hippocampal neurons was observed on well-packed structures of silica beads with diameters in excess of 200 nm, which is comparable with the thickness of filopodia.[12,13]

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Conclusion