Longitudinal and Noninvasive Intracellular Recordings of Spontaneous Electrophysiological Activity in Rat Primary Neurons on Planar MEA Electrodes.

Presently, the in vitro recording of intracellular neuronal signals on microelectrode arrays (MEAs) requires complex 3D nanostructures or invasive and approaches such as electroporation. Here, it is shown that laser poration enables intracellular coupling on planar electrodes without damaging neurons or altering their spontaneous electrophysiological activity, allowing the process to be repeated multiple times on the same cells. This capability distinguishes laser-based neuron poration from more invasive methods like electroporation, which typically serve as endpoint measurement for cells. It is demonstrated that planar MEA electrodes, when combined with laser cell optoporation and live cell staining, can record spontaneous intracellular signaling from primary neurons in vitro. This approach allows for the detection of attenuated signals resembling positive monophasic intracellular action potentials. Recordings after laser optoporation also reveal subthreshold signals such as post-synaptic potentials that are essential for assessing neuronal network plasticity and connectivity. Moreover, the noninvasiveness of the process enables repeated intracellular recordings over multiple days from the same cells.