A feasibility study of multi-site,intracellular recordings from mammalian neurons by extracellular gold mushroom-shaped microelectrodes

Abstract

The development of multi-electrode array platforms for large scale recording of neurons is at the forefront of neuro-engineering research efforts. Recently we demonstrated, at the proof-of-concept level, a breakthrough neuron-microelectrode interface in which cultured Aplysia neurons tightly engulf gold mushroom-shaped microelectrodes (gMμEs). While maintaining their extracellular position, the gMμEs record synaptic- and action-potentials with characteristic features of intracellular recordings. Here we examined the feasibility of using gMμEs for intracellular recordings from mammalian neurons. To that end we experimentally examined the innate size limits of cultured rat hippocampal neurons to engulf gMμEs and measured the width of the “extracellular” cleft formed between the neurons and the gold surface. Using the experimental results we next analyzed the expected range of gMμEs-neuron electrical coupling coefficients. We estimated that sufficient electrical coupling levels to record attenuated synaptic- and action-potentials can be reached using the gMμE-neuron configuration. The definition of the engulfment limits of the gMμEs caps diameter at ≤2–2.5 μm and the estimated electrical coupling coefficients from the simulations pave the way for rational development and application of the gMμE based concept for in-cell recordings from mammalian neurons.

On-chip, multisite extracellular and intracellular recordings from primary cultured skeletal myotubes

“…The ultrastructural observations described above revealed that a fraction of the gMμE-MEA were tightly engulfed by cultured myotubes in a similar manner to that described by our laboratory for cultured Aplysia neurons, cardiomyocytes and rat hippocampal neurons2829303132333443. The tight engulfment of the gMμEs by myotubes provides the necessary structural basis to obtain Ohmic access to the myotube sarcoplasm and IN-CELL recording configurations.…”

“…was in the range of 100 μV, in the present study the average amplitudes for positive monophasic FPs were 1279 ± 146 μV (n = 148); for negative monophasic FPs 711 ± 66 μV (n = 45) and for the biphasic FPs 1221 ± 1045 μV (n = 557). The improved recording quality of the gMμE-MEA over substrate integrated planar MEA can be attributed to the increased seal resistance formed between the myotubes’ plasma membrane and the gMμE by its engulfment293031324348. Consistent with this hypothesis, the variability in the FP amplitudes is related to the level of gMμE engulfment by the cells43.…”

“…The well preserved appearance of the subcellular organelles in the TEM images suggested that the fixation, dehydration and embedding procedures did not produce significant ultrastructural artifacts. Nevertheless, it is important to recall that the extracellular cleft formed between the plasma membrane of living cells and artificial substrates such as the gMμPs may reflect varying degrees of artifacts induced by the processing of the samples for TEM analysis3543. A number of studies have estimated that the processing of tissues for TEM imaging induces “shrinking artifacts” in the range of 5–17%4445.…”

“…5e). The small differences in the shapes of the APs can be ascribed to the filtering effects of the gMμE and the AC MEA amplifiers and the DC amplifier used for recording the potentials by the sharp glass electrodes33354352.…”

“…8d) was represented by a resistor (Rs), taking into account the medium’s specific resistance, electrical dynamics, the geometric properties of the membrane and the gMμE2043. The gMμE was represented by a constant phase element (CPE) and a resistor in parallel (R EP ).…”