Brain Function: Novel Technologies Driving Novel Understanding - Bioinspired Approaches for Human-Centric Technologies - page 318

Fig. 10.11 Focused ion beam deposition of nanoprotrusions with different shapes and sizes on top
of a MEA substrate for comparative analysis on the mechanisms of interaction with cultured
neurons. On the left-hand side , from top to bottom , SEM pictures of nanopillar, nail-headed, and
sphere-headed nanoprotrusions (scale bar of 1 μ m). On the right-hand side ,5 5 arrays of
different nanoprotrusions as fabricated on targeted pads of the MEA. Figure adapted from
Martiradonna et al. ( 2012 )

wrapped by neurites extending from neurons attached on the flat insulating layer
between the electrodes (Fig. 10.12 ), and all three kinds of nanostructures readily
sustained cellular projections. In particular, a guiding effect was observed in the
case of straight nanopillars (Fig. 10.12b ). Sometimes, neurites were seen to form
suspended bridges between adjacent pillars, while in other cases, they contacted the
underlying gold pad and were only partially guided by the nanostructures. In
contrast, nail-headed and sphere-headed pillars promoted the formation of a
dense network completely detached from the substrate.
This tendency of cells to engulf nanoprotrusions could be used to enhance
correspondence between neurons and the recording sites of a MEA. For example,
we fabricated 2 m pitch) of either straight or nail-headed

nanopillars on an active-pixel sensor microelectrode array (Fig. 10.13 ).
Nanostructures were made of both conductive platinum and low-conducting silicon
dioxide to distinguish the contributions to the neuron/electrode electrical coupling
of the tight attachment and of the reduced electrode impedance. Rat hippocampal
neurons were cultured on the substrate after functionalization with PLL. Cells
readily engulfed all types of FIB-fabricated nanostructures (Fig. 10.14 ) (Sileo
et al. 2013 ). The figure also highlights the use of the dual-beam system to also
visualize the fine structure of the cell-probe interface.
Another nanostructure morphology with considerable potential for neuroscience
applications is 3D hollow nanocylinders (De Angelis et al. 2013 ), which could
allow novel ways to interface with neurons. At IIT, hollow nanostructures were
fabricated using common polymers and with a novel FIB technique applied on

2 arrays (2.5 μ