Molecular design and characterization of the neuron–microelectrode array interface

Electrophysiological activities of neuronal networks can be recorded on microelectrode arrays (MEAs). This technique requires tight coupling between MEA–surfaces and cells. Therefore, this study investigated the interface between DRG neurons and MEA–surface materials after adsorption of neurite promoting proteins: laminin-111, fibronectin, L1Ig6 and poly-l-lysine. Moreover, substrate-induced effects on neuronal networks with time were analyzed. The thickness of adsorbed protein layers was found between ∼1 nm for poly-l-lysine and ∼80 nm for laminin-111 on platinum, gold and silicon nitride. The neuron-to-substrate interface was characterized by Scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and SEM after in situ focused-ion-beam milling demonstrating that the ventral cell membrane adhered inhomogeneously to laminin-111 or L1Ig6 surfaces. Tight areas of 20–30 nm and distant areas <1 μm alternated and even tightest areas did not correlate with the physical thickness of the protein layers. This study illustrates the difficulties to predict cell-to-material interfaces that contribute substantially to the success of in vitro or in vivo systems. Moreover, focused ion beam (FIB)/SEM is explored as a new technique to analyze such interfaces.