Revealing the Cell–Material Interface with Nanometer Resolution by Focused Ion Beam/Scanning Electron Microscopy

Abstract

The interface between cells and non-biological surfaces regulates cell attachment, chronic tissue responses, and ultimately the success of medical implants or biosensors. Clinical and laboratory studies show that topological features of the surface profoundly influences cellular responses, e.g. titanium surfaces with nano- and microtopographical structures enhance osteoblast attachment and host-implant integration as compare to smooth surface. To understand how cells and tissues respond to different topographical features, it is of critical importance to directly visualize the cell-materials interface at the relevant nanometer length scale. Here, we present a new method for in situ examination of the cell-to-material interface at any desired location, based on focused-ion beam milling and scanning electron microscopy imaging (FIB-SEM) to resolve the cell membrane-to-material interface with 10 nm resolution. By examining how cell membranes interact with topographical features such as nanoscale protrusions or invaginations, we discovered that the cell membrane readily deforms inward and wraps around protruding structures, but hardly deforms outward to contour invaginating structures. This asymmetric membrane response (inward vs. outward deformation) causes the cleft width between the cell membrane and the nanostructure surface to vary for more than an order of magnitude. Our results suggest that surface topology is a crucial consideration for the development of medical implants or biosensors whose performances are strongly influenced by the cell-to-material interface. We anticipate that the method can be used to explore the direct interaction of cells/tissue with medical devices such as metal implants in the future.

Rational Design of Semiconductor Nanostructures for Functional Subcellular Interfaces

“…Bianxiao Cui’s and Yi Cui’s Laboratories have demonstrated that nanopillar arrays can minimally invasively pin embryonic cortical neuronal cell bodies 39 and, more recently, that plasma membranes of HL-1 cardiomyocytes cultured on a quartz substrate with nanopillars can deform to wrap around the pillars but will not readily deform outwardly around invaginating structures (Figure 2C,D). 40 This differential membrane response to varying nanoscale topographical features must be considered during design of materials to be implanted into biological systems, as the tightness of the interface can vary significantly. At the membrane protein level, it was found that positively curved membranes are clathrin-mediated endocytosis (CME) hot spots.…”

“…(C,D) Surface topography affects cleft distance between cell membrane and material surface. Adapted with permission from ref 40. Copyright 2017 American Chemical Society.…”

Neurospheres on Patterned PEDOT:PSS Microelectrode Arrays Enhance Electrophysiology Recordings

“…The cross-section was performed as presented in ref. [21] using a focused ion beam (FIB) prepared sample (see Experimental Section). The image demonstrates the coverage of PEDOT:PSS on gold, the encapsulation of parylene around it and most importantly, the tight attachment of the cell on the microelectrode.…”

“…For the cross-sectional images, the cells were further processed with a ROTO staining, uranyl acetate, dehydrated, and embedded as presented in ref. [21]. Cross-sections were made and polished, fixing a voltage at 30 kV and current at 80 pA. A more detailed description of the FIB-SEM procedure is given in ref.…”

“…Cross-sections were made and polished, fixing a voltage at 30 kV and current at 80 pA. A more detailed description of the FIB-SEM procedure is given in ref. [21]. Image acquisition of the cross-section was performed with a backscattered detector at 3-10 kV and at variable currents.…”