Neurotoxicology and Safety

Neurotoxicology
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Neurotoxicity occurs when a substance alters the normal neuron function and may manifest as seizures, cognitive decline, loss of motor function, or behavioral problems. Traditional cytotoxicity measurements, like cell death, are easy to measure, but insufficient at identifying functional impairment in cell communication, which often occurs before or even in the absence of cell death.

The Maestro MEA system has the sensitivity to measure a single neuron firing and electrode number to capture the network level activity. The noninvasive and continuous measurement capabilities of the Maestro system, including environmental control, can capture acute or chronic responses, creating an ideal model for studying neurotoxicity and assessing compound risk.

 

Measuring seizurogenic/proconvulsant risk

The Maestro Pro and Edge multiwell MEA platforms are an effective laboratory tool for high-throughput in vitro screens of neuroactive compounds (McConnell et al 2012, Valdivia et al 2014). Basic metrics, such as weighted mean firing rate, are sensitive to many neuroactive compounds, while advanced metrics, such as network bursting and synchrony, provide provide reliable identification of compounds that increase or suppress seizurogenic activity and, more broadly, affords discrimination between various compound classes. In the example below, 16 compounds were dosed sequentially with 6 replicates across 2 plates.

Comparison of network bursts under different drug conditions.

 

Network burst magnitude (number of spikes per burst) clearly discriminates proconvulsants, like picrotoxin, from the vehicle control.

Synchrony, as measured by the full width at half height of the cross correlogram (FWHH), differentiates proconvulsant compounds from other classes. Proconvulsant compounds exhibit increased synchrony, while antiepileptics exhibit decreased synchrony.

Neurotoxicology synchronicity data

 

Neurotox protocol

Getting started with Maestro Pro and Edge couldn't be easier. Culture your neurons in an Axion multiwell MEA plate (Day 0).  Load the MEA plate into the Maestro MEA system at the desired recording times and begin recording.  Analyze the neural activity in the MEA plate label-free and in real-time with AxIS Navigator Neural Module software.  Add test compounds as required (e.g. Day 7).

 

 

Maestro MEA user

 

The advantage of measuring neurotoxicology and safety on the Maestro Pro and Edge systems:

  • Measure what matters – The Maestro Pro and Edge MEA systems directly measure neuronal action potentials. Indirect measurements like calcium imaging are unable to capture important but subtle changes to neural network signaling while gene and protein expression are insufficient to characterize function. The Maestro MEA platforms track activity in real-time, enabling you to answer the question that matters: Do your neurons fire as expected?

  • Analyze cell activity label-free – Measure the same culture over hours, weeks, and months while avoiding dyes and reporters that can alter your biology and confound results.

  • Probe cell models in the same plate they were cultured in – Neurons exist as a functional network of inter-linked cells. The Maestro MEA platforms preserve the complex functionality of your neural models. Platforms that require single-cell suspensions (automated patch clamp, flow cytometry), require more sample handling and destroy the networks that define the functionality of these neural cultures.

  • It's easy – You don't have to be an electrophysiologist to use the Maestro MEA system. Just culture your neurons in an MEA plate, load your plate into the Maestro MEA system, and record your neural data. Axion's data analysis tools will do the rest, even generating the publication-ready graphs you need.

Neural MEA technology

Neural MEA

 

What is a microelectrode array (MEA)?

Microelectrode arrays (MEA), also known as multielectrode arrays, contain a grid of tightly spaced electrodes embedded in the culture surface of the well. Electrically active cells, such as neurons, are plated and cultured over the electrodes. When neurons fire action potentials, the electrodes measure the extracellular voltage on a microsecond timescale. As the neurons attach and network with one another, an MEA can simultaneously sample from many locations across the culture to detect propagation and synchronization of neural activity across the cell network.

That’s it, an electrode and your cells. Since the electrodes are extracellular, the recording is noninvasive and does not alter the electrophysiology of the cells - you can measure the activity of your culture for minutes, days, or even months!

CytoView well bottom

An MEA of 64 electrodes embedded in the substate at the bottom of a well.

Rendering of cells growing over the electrodes at the bottom of the well

Neurons attach to the array and form a network. The microelectrodes detect the action potentials fired as well as their propagation across the network.

 

 

 

Brain waves in a dish

Neurons communicate with other cells via electrochemical signals. Many neural cell types form cellular networks, and MEAs allow us to capture and record the electrical activity that propagates through these networks.

Neurons fire action potentials that are detected by adjacent electrodes as extracellular spikes. As the network matures, neurons often synchronize their electrical activity and may exhibit network bursts, where neurons repeatedly fire groups of spikes over a short period of time.

The MEA detects each cell's activity, as well as the propagation of the activity across the network, with spatial and temporal precision. Patterns as complex as EEG-like waveforms, or "brain waves in a dish", can be observed. Axion's MEA assay captures key features of neural network behavior as functional endpoints - activity, synchrony, and network oscillations.

Action potentials recorded from electrodes

Action potentials are the defining feature of neuron function. High values indicate frequent action potential firing and low values indicate the neurons may have impaired function.

Synchrony reflects the prevalence and strength of synaptic connections, and thus how likely neurons are to generate action potentials simultaneously

Synapses are functional connections between neurons. Synchrony reflects the prevalence and strength of synaptic connections, and thus how likely neurons are to generate action potentials simultaneously on millisecond time scales.

Network oscillations, or network bursting, are defined by alternating periods of high and low activity

Network oscillations, or network bursting, as defined by alternating periods of high and low activity, are a hallmark of functional networks with excitatory and inhibitory neurons. Oscillation is a measure of how the spikes from all of the neurons are organized in time.

 

Do more with multiwell

Axion BioSystems offers multiwell plates, ranging from 6 to 96 wells, with an MEA embedded in the bottom of each well. Multiwell MEA plates allow you to study complex neural biology in a dish, from a single cell firing to network activity, across many conditions and cell types at once.