Mapping cell behavior across a wide range of vertical silicon nanocolumn densities

Abstract

Over the past decade, vertical nanostructures have provided novel approaches for biomedical applications such as intracellular delivery/detection, specific cell capture, membrane potential measurement, and cellular activity regulation. Although the feasibility of the vertical nanostructures as a new biological tool has been thoroughly demonstrated, a better understanding of cell behavior on vertical nanostructures, in particular the effects of geometry, is essential for advanced applications. To investigate the cell behavior according to the variation of the spacing between vertical nanostructures, we have interfaced fibroblasts (NIH3T3) with density-controlled vertical silicon nanocolumn arrays (vSNAs). Over a wide range of vSNA densities, we observe three distinct cell settling regimes and investigate both overall cell behavior (adhesions, morphology, and mobility) and detailed biomacromolecule variance (F-actin and focal adhesion) across these regimes. We expect that these systematic observations could serve as a guide for improved nanostructure array design for the desired cell manipulation.

High‐Aspect‐Ratio Nanostructured Surfaces as Biological Metamaterials

“…The model also suggests that membrane wrapping around the nanowire is not normally energetically favorable and requires external force. They were able to verify their model against literature and experimental data, also observing an intermediate settling between the fully deformed and on‐top regimes.…”

“…The main challenge for all investigations of high‐aspect‐ratio nanostructured surfaces is deconvoluting the influence of geometry, material properties, surface chemistry, and differing biological response. Incorporating a range of parameters, e.g., systematically changing geometry or testing multiple cell lines, into the experimental design can help. Approaches such as image‐based cell profiling can help to quantitatively analyze large numbers of cells, adding statistical weight to conclusions, as well as in identifying subpopulations and other effects driven by cell heterogeneity .…”

“…The result of Xie et al highlighting the lack of spontaneous penetration provided an assumption (exploited in later models) that to effectively understand cell behavior, the balance of free energy of the membrane (rather than gravitational force) should be considered. Martinez and co‐workers have extensively studied geometry‐dependent cell response both experimentally and theoretically . Their model considers the cell as a soft‐shelled droplet, and defines the free energy of the cell–substrate interaction as the sum of the cell–substrate adhesion, the change in surface tension caused by an increase in cell surface area, and the change in elastic energy caused by bending the membrane .…”

“…Nanosphere lithography (also referred to as colloidal lithography) uses the self‐assembly of polymer or microgel‐based nanospheres on a surface . A wide range of variants exist, for a more in depth discussion see the review of Wang et al Controlling the type and size of particle deposited, the surface chemistry, and deposition conditions allows either well‐defined high‐density packing or lower‐density stochastic patterns …”

“…Where the substrate is a semiconductor such as silicon, metal‐assisted chemical etching can be used for anisotropic wet etching. This process uses a patterned metal layer on the substrate surface to selectively catalyze the etch reaction, and has been widely used to create high‐aspect‐ratio nanostructures for cell and tissue interfacing . Metal is deposited in unprotected regions on a surface by evaporation or an electroless‐deposition technique .…”