Cell Imaging on UltraSM® Nano-Porous Ultra-thin Silicon Membranes
The UltraSM® silicon membrane provides a first-in-class combination of imaging and cell growth abilities for optical and electron microscopy. This ultra-thin membrane permits imaging of cells by either light, fluorescent or electron microscopic methods. The millions of nanopores within the membrane allow two cell types on either side of the membrane to communicate with one another. The cells can be physically separated and imaged by optical means due to the excellent optical characteristics of the UltraSM® membrane. Together, these properties make the UltraSM® silicon membrane an ideal substrate for growth and imaging of single or multiple cell-type cultures.
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Growth & Viability of Cells
Cell adhesion to, and observed growth rates on, UltraSM® silicon membranes are equivalent to conventional tissue culture plastic or glass cover slips. The silicon composition of UltraSM® membranes is biocompatible, unlike carbon films on cytotoxic, metallic grids. The native silicon oxide film on the membrane contributes a slight negative charge and a glass-like, cell-friendly surface for attachment and growth.
To date, the following cell types have been successfully cultured on UltraSM® silicon membranes:
Primary human umbilical vein endothelial (HUVEC)
Human neutrophils
Human/mouse T-cells and Tregs
NG108-15 - mouse neuroblastoma and rat glioblastoma hybrid
bEnd.3 - brain endothelial
3T3 fibroblasts
The nanometer thickness of the UltraSM® silicon membrane, at specified thicknesses of 15 or 30 nm, is thin enough to allow light and electrons to pass without significant diffraction. The millions of 10-50 nm diameter nanopores within this membrane create a highly permeable film which allows cells grown on either side of the membrane to communicate with diffusible signaling molecules. Traditional polymer membranes used in cell culture are ~1,000-times thicker, have pores that follow tortuous paths through the membrane, trap diffusible molecules and keep cells on either side of the membrane at non-physiological distances from one another.
TEM image of the UltraSM® membrane, where the dark spots correspond to silicon crystals diffracting the beam and the white areas correspond to open nanopores.
For multiple cell-type culture models, the UltraSM® membrane is a breakthrough. It enables co-culture of multiple cell types in a setting where the cells can communicate with one another by short-range signals and be maintained at physiologically meaningful distances across the membrane. Combined with the ability to image and analyze both cells on either side of the membrane, the UltraSM® membrane is an ideal substrate for many co-culture studies.
Optical Characteristics
Intracellular details can be resolved within cells grown on UltraSM®
silicon membranes. Typical polymer membranes used for cell culture are
too thick to allow detailed resolution of intracellular structures.
These polymer membranes are also incompatible with fluorescent imaging
methods due to significant background caused by membrane
auto-fluorescence. The silicon composition of UltraSM® membranes
eliminates concerns over auto-fluorescence, permitting fluorescent
imaging at near-UV excitation and emission.
UltraSM® provide ability to visualize intracellular detail
Electron Microscopy of Cells
Cells can be imaged on UltraSM® silicon membranes using electron microscopy methods as well. The added ability to correlate light, fluorescent and electron microscopy images is possible. The silicon composition of UltraSM® membranes is sufficiently conductive for SEM imaging without any carbon or gold coating and should allow current dissipation to prevent specimen charging under more intense beam currents.
This example shows an image where neutrophils were fixed, dried and imaged by SEM (no staining or gold-sputtering was required). It is also possible to culture cells on the grids prior to imaging. In this case, these neutrophils were pipetted onto the grids prior to preparation.
Intracellular details can be resolved within cells grown on UltraSM®
silicon membranes. Typical polymer membranes used for cell culture are
too thick to allow detailed resolution of intracellular structures.
These polymer membranes are also incompatible with fluorescent imaging
methods due to significant background caused by membrane
auto-fluorescence. The silicon composition of UltraSM® membranes
eliminates concerns over auto-fluorescence, permitting fluorescent
imaging at near-UV excitation and emission.