The preparation of biological cells for either scanning or transmission electron microscopy requires a complex process of fixation, dehydration and drying. Critical point drying is commonly used for samples investigated with a scanning electron beam, whereas resin-infiltration is typically used for transmission electron microscopy. Critical point drying may cause cracks at the cellular surface and a sponge-like morphology of nondistinguishable intracellular compartments. Resin-infiltrated biological samples result in a solid block of resin, which can be further processed by mechanical sectioning, however that does not allow a top view examination of small cell-cell and cell-surface contacts. Here, we propose a method for removing resin excess on biological samples before effective polymerization. In this way the cells result to be embedded in an ultra-thin layer of epoxy resin. This novel method highlights in contrast to standard methods the imaging of individual cells not only on nanostructured planar surfaces but also on topologically challenging substrates with high aspect ratio three-dimensional features by scanning electron microscopy.

The complexity of the extracellular matrix consists of micro‐ and nanoscale structures that influence neuronal development through contact guidance. Substrates with defined topographic cues mimic the complex extracellular environment and can improve the interface between cells and biomedical devices as well as potentially serve as tissue engineering scaffolds. This study investigates axon development and growth of primary cortical neurons on OrmoComp nanopillars of various dimensions. Neuronal somas and neurites form adhesions and F‐actin accumulations around the pillars indicating a close contact to the topography. In addition, higher pillars (400 nm) confine the growing neurites, resulting in greater neurite alignment to the topographical pattern compared to lower pillars (100 nm). A comprehensive analysis of growth cone dynamics during axon development shows that nanopillars induce earlier axon establishment and change the periodicity of growth cone dynamics by promoting elongation. This results in longer axons compared to the flat substrate. Finally, the increase in surface area available for growth cone coupling provided by nanopillar sidewalls is correlated with increased assembly of paxillin‐rich point contact adhesions and a reduction in actin retrograde flow rates allowing for accelerated and persistent neurite outgrowth.

Accelerated neurite outgrowth of rat cortical neurons on a flexible and inexpensive substrate functionalized with gold nanocone arrays is reported. The gold nanocone arrays are fabricated on Teflon films by a bottom-up approach based on colloidal lithography followed by deposition of a thin gold layer. The geometry of nanocone arrays including height and pitch is controlled by the overall etching time and template polystyrene beads size. Fluorescence microscopy studies reveal high viability and significant morphological changes of the neurons on the structured surfaces. The elongation degree of neurite is maximized on the nanocone arrays created with 1 µm polystyrene beads by a factor of two with respect to the control. Furthermore, the interface between the neurons and the nanocones is investigated by scanning electron microscopy and focused ion beam cross-sectioning. The detailed observation of the neuron/nanocone interfaces reveals the morphological similarity between the nanocone tips and the neuronal processes, the existence of interspace at the interface between the cell body and the nanocones, and neurite bridging among the neighboring structures, which may induce the acceleration of neurite outgrowth. The flexible gold nanocone arrays can be a good supporting substrate of neuron culture with noble electrical and optical properties.

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