Controlled outgrowth and synapse formation of rat brain neurons by microcontact printing

Micro contact printing of biomolecules is known as an efficient approach for guiding neuronal cell migration and outgrowth on artificial substrate surfaces. When appropriate surface chemistry and microstructures are chosen, neurons are growing according to the defined geometry of the pattern. In the present study, cortical and hippocampal neurons of rats (E15-E18) were cultured on laminin, laminin/polylysine, and polylysine patterned substrates, such that small neuronal networks with a defined geometry were obtained. The interconnections between neighbouring pairs of neurons within these artificial networks were assessed electrically by double and triple patch-clamp recordings and optically by phase contrast and fluorescence microscopy. Both functional and ohmic synapses were detected. Based on the recorded data and simulations in PSpice, an electrical model for ohmically coupled cells was derived. The functional synapses were evaluated in regard of the average synaptic transmission, the average excitatory post synaptic potential (EPSP), and the average signal transmission delays of synapses. It could be shown that functional synapses on patterned substrates behave very similar to those on unpatterned, homogeneous cultures.