Precision and Stability: Cellular-level imaging solutions for electrophysiology

What is electrophysiology? 

Electrophysiology is a specialized branch of physiology. It’s the study of the electrical properties and activity in biological cells and tissue, and combines biology, physics, neuroscience, and engineering to achieve results. 

Electrophysiological researchers measure the minute voltage changes occurring within individual cells—typically on the scale of 20-30 microns—providing critical insights into cellular function, neural communication, and disease mechanisms. They may investigate: 

• Membrane potential: The voltage difference across a cell membrane, typically ranging from -70 to -90 mV in resting neurons. 

• Action potentials: Brief, all-or-nothing electrical events that serve as the fundamental units of neural communication, lasting 1-2 milliseconds. 

• Synaptic potentials: Localized voltage changes that occur when neurotransmitters bind to receptors on the postsynaptic membrane. 

• Ion channel kinetics: The opening and closing patterns of specific membrane channels that regulate ionic flow across the cell membrane. 

• Capacitance: A measure of a cell's ability to store charge, providing insights into cell size and morphology. 

Precision and stability are crucial in any electrophysiology experiment. The electrical signals involved are very subtle – often measured in millivolts or microvolts – and interference due to vibration or electrical noise is a risk to the integrity of the results. The small scale requires nanometer precision: experimenters may use electrodes with tips as small as 0.5 µm to navigate to specific cellular targets within a sample.  

Typical applications for electrophysiology 

Electrophysiological techniques are used in a range of research and clinical applications: 

• Neuroscience: To record activity from neurons, map neural circuits, or study conditions such as epilepsy or neurodegenerative diseases. 

• Cardiology: To investigate the electrophysiological properties of heart cells, contributing to the understanding of arrhythmias and heart failure. 

• Pharmacology and Toxicology: To assess how drugs or environmental toxins affect cellular electrical activity. 

• Basic Cell Biology: To explore the function of ion channels, membrane transport, and other fundamental processes. 

Each application requires the ability to target and observe individual cells with high spatial and temporal resolution. 

Imaging techniques for electrophysiology 

Electrophysiology experiments often combine multiple imaging modalities: 

• Fluorescence Imaging enables visualization of specific structures or molecules using dyes, labels, or genetically encoded indicators such as voltage-sensitive fluorescent proteins. 

• Brightfield Microscopy is frequently used to navigate and locate the target cells, offering a clear view of general tissue morphology. It gives clear structural visualizations and provides excellent contrast for identifying target regions and cell boundaries in unstained preparations. With less light intensity, there is less risk of photobleaching than with fluorescence.  

• Multiphoton Microscopy is used for imaging living tissues and cells in animals.  A type of fluorescence microscopy, it uses a low-energy wavelength of light, often infrared, which not only ensures minimal phototoxicity but also enables deeper penetration into tissues. Label-free imaging of tissues is also becoming more prevalent, with biological structures such as collagen exhibiting second (SHG) and third (THG) harmonic generation. This type of imaging relies on the use of infrared wavelengths emitted from a pulse laser source.  

• Calcium Imaging is not the same as electrophysiology but is related. Whereas electrophysiology measures the electrical activity in individual neurons, calcium imaging measures electrical signals in many neurons simultaneously. It is a useful technique to understand synaptic transmission or the operation of part of a nervous system. Used in combination with another electrophysiology technique, researchers can build a more complete understanding of neuronal activity by combining spatial and temporal information. It also has uses in plant science research.  

• Real-time visualization techniques enable electrophysiologists to capture rapid events – such as the firing of specific neurons – and get immediate feedback. In advanced systems, the imaging capabilities combine with data acquisition to create a unified platform where imaging and recording work in concert rather than as separate components.  

Learn more: Prior designs advanced three-camera system for neurobiology 

Challenges in Electrophysiology Imaging 

One of the defining characteristics of electrophysiology experiments is the need for extreme sample stability. Even the slightest movement can disrupt electrode positioning, compromise measurements, or render fluorescence imaging unusable. Large samples and bulky peripheral equipment can be a further complication.  

This creates several challenges for electrophysiology researchers: 

• No movement can be tolerated: The sample must remain completely static during imaging. This is often achieved using either an active or passive anti-vibration table as the base for the experiment.  

• Precision targeting: Only one or two cells may be observed at a time, which requires fine motion control. 
  Electrophysiologists use a combination of XY and Z platforms and piezo nanopositioning stages to move either the sample or the microscope to the area of interest, then use micromanipulators to insert the electrodes into the tissue. Any equipment used must not only move with sub-micron precision, it must also maintain a stable position for a long time, possibly with a heavy load.  

• Large variation in sample sizes: The same instrument may be used to image whole animals or individual cells. Any microscope or imaging platform used must be adaptable to avoid disrupting complex and sensitive peripherals or creating the need to duplicate sets of expensive hardware. Experiments where animals are moving or are responding to external stimuli further compound this challenge.  

• Complex set ups: Simultaneous modalities that combine optical imaging (e.g., fluorescence) with electrical recording techniques like patch-clamp or field potential measurements require customized imaging systems, often combining equipment from several suppliers. Electrophysiology systems typically also have a high level of customization relative to the specific experiment being undertaken.  

• Delicate, live samples need extra care: As well as the risk of photobleaching during fluorescence imaging, live cell samples require incubators – which further complicates the experiment.  

• Small electrical signals require shielding/low noise to avoid interference: Electrical amplifiers may be used but add to the amount of peripheral equipment added to the platform.  

Selecting the right equipment for electrophysiology  

At Prior we understand the complex needs of electrophysiology, such as the need to integrate multiple imaging techniques with large samples and bulky peripheral equipment – all without compromising the electrophysiological recording.  

Our physiology platforms offer high-precision motorized and manual movement on the X, Y, and Z axes. They have large surface areas for imaging whole animals or for mounting peripherals for complex experiments. These include: 

• HZ106 and H189: feature motorized Z-axis, up to 25 kg weight capacity, and multiple decks to accommodate a greater variety of sample size.  

• Z Deck platform: offers long Z-axis travel, with a motorized version for automated microscopy and manual version for experiments where low electrical noise is paramount.  

• HT11 Series: Heavy duty stage for automated scanning of large samples with load capacity up to 100 kg.  

• Translation stages provide a stable platform to move the microscope while keeping the sample stationary. This enables different areas to be imaged without disturbing any other imaging system components such as patch clamps.  

High-precision piezo objective positioners are essential to ensure the high resolution and repeatability needed for multiphoton microscopy. The OP800 nanopositioning objective scanner provides the fastest step settle time of any piezo-driven objective positioner with a long range of up to 800 µm. This extended travel range is ideal for multiphoton as it takes advantage of the penetration depth of infrared wavelengths to image further into the sample or create larger image volumes.  

Browse our imaging components to discover our ranges of microscope parts, accessories, and XY motorized stages. 

Antivibration tables ensure additional stability for highly sensitive equipment, where interference from traffic or footsteps poses a risk. Prior is experienced in sourcing and integrating a wide variety of third-party equipment.  

Customized imaging systems using Prior’s modular OpenStand platform allows users to combine a range of third-party equipment, Prior’s imaging components, and our engineering expertise to create a unique system. Because OpenStand is modular, upgrading or adapting to meet new experimental challenges is cost-effective and easy. Contact us to learn more.