Automated Patch Clamp: A Chip-based Planar Patch Clamp Approach
The patch clamp technique is the gold standard for real-time investigation of ion channels. With its exceptional signal resolution, complex biophysical properties and effectors of ion channels can be studied.
The automation of the patch clamp method was made possible with the development of the chip-based planar patch clamp technology. Automated patch clamp increases throughput and ease of use compared to the conventional patch clamp technique making it accessible to a wider audience.
Nanion has been the 'first on the market' with the launch of the semi-automated planar patch clamp device, the Port-a-Patch, in 2003. Since then, we have developed further instruments which are all "true Giga-seal" devices and offer a wide variety of experimental possibilities based on the planar patch clamp technology, expanding on the capabilities of conventional patch clamp.
Patch Clamp Explained
Ion Channels are pore-forming proteins in cell membranes that allow the flow of ions across the membrane. Today, more than 30 ion channel and ion channel-related families are known. Ion channels are regulated by specific signals as voltage changes over the membrane (voltage-gated ion channels), intra- and extracellular binding ligands (ligand-gated ion channels), temperature, pH or mechanical stress. Each ion channel shows a specific conductancy for specific ions, as potassion, sodium or chloride. Ion channels are expressed by excitable cells, establishing a resting potential or shaping action potentials. Ion channels are furthermore expressed by epithelial or secretory cells and are involved in cell volume regulation.
Patch Clamp Technology
Patch Clamp Technology is an electrophysiological technique to analyze ion channels in cells or membranes. Ions flowing through a single ion channel cause a current in the range of picomperes. Powerful amplifiers are used to measure either the voltage change (current clamp technology) or the current flow (voltage clamp technology) across the membrane upon the opening and closing process of ion channels. As a prerequisite, two electrodes are placed/ will be given electrical access to either one side of the membrane. With the patch clamp technology, it is possible to measure single ion channels within a membrane, e.g. a vesicle or lipid bilayer (single channel analysis) in the range of 5 picoamperes or the sum of ion channels within the the membrane of a cell or vesicle in the range of hundred to few thousand picoamperes (whole cell).
Planar Patch Clamp
Planar Patch Clamp is a chip-based approach to patch cells or vesicles: The chip contains a tiny whole (approx. 10 - 20 times smaller than the cell/ vesicle) which catches a floating cell out of a cell suspension via negative pressure. To give electrical access (inner electrode) to the inner part of the cell, either the cell is ruptured by stronger suction pulses though the tiny whole (whole cell technology), or a pore-forming agent is perfused through the microchannels of the small chip-whole (perforated patch). In comparison to conventional patch clamp where an electrode-containing glas pipette is moved to the cell under microscopic control, in planar patch clamp the cell is moved to the pipette (or more accurate chip whole). Planar patch clamp technology was utilized in all our devices, as it simplifies the methodology and enabled us to automate the patch clamp technology.
High Quality Patch Clamp Data
High quality patch clamp results are achieved when the gap between cell membrane and pipette (chip whole) is as little as possible to prevent short circuits. This gap is measurable as resistance (Ohm). A Gigaseal is a seal of one or more Gigaohm which is mandatory for most ion channel analyses. The series resistance or access resistance is the resistance from the inner electrode to the inner part of the cell. A high access resistance might cause a poor ion channel control via a poor voltage or current clamp as well as a poor measurement of ion channel activity. It is important that neither the seal resistance nor the access resistance changes during the measurement, as this falsifies the measurement of the ion channel activity and may cause an artificial runup or rundown of the current response in voltage clamp studies. In case of the analysis of small currents (e.g. for single channel measurements), a good signal-to-noise ratio of the system is important. A low electrocal noise of the setup is achieved by a good shielding (Faraday cage) and powerful amplifiers.
The success rate is the proportion of measured cells in a patch clamp study with an automated patch clamp device that passed all defined quality criteria e.g. a specific seal resistance, access resistance, peak current. The success rate is dependant on multiple factors as the cell quality (e.g. ion channel expression) including cell culturing and dissociation protocol, or in case of lipid bilayer measurements a good membrane preparation, used buffers, chosen chip types and study design (e.g. chosen voltage clamp pulse protocol). Please ask our experts for protocols and advices for your assay optimization.
History of Planar Patch Clamp
Patch Clamp: How it started
In the late 1970s, Bert Sakmann and Erwin Neher developed the voltage-clamp technique and resolved single channel currents across a membrane patch of a frog skeletal muscle. In 1980, Ernst Sakmann invented the gigaseal which improved the signal-to-noise ratio and allowed the recording of even smaller currents. In 1991, Bert Sakmann and Erwin Neher were honored with the Nobel Prize in Physiology and Medicine.
The idea of Planar Patch Clamp
Features and Applications of Automated Patch Clamp Devices
Features of Patch Clamp Devices
Important Features of automated patch clamp devices are mandatory to measure specific ion channel families: Fast-activating ligand-gated ion channels (e.g. the nicotinic Acetylcholin receptor Alpha 7) are activated within some milliseconds. For these, it is necessary to have an ultrafast external perfusion system. Most ion channels are temperature sensitive or show different kinetics and compound block effects at different temperatures (e.g. hERG), for reproducable measurements a temperature control is mandatory. A strong advantage of the planar patch clamp technology compared to conventionsal patch clamp is the intracellular perfusion of compounds or substances via the automated liquid handling system, allowing the measurement of e.g. TRP channels, activated by intracellular calcium. Another advantage of planar patch clamp is population patch clamp, allowing ionic currents to be measured from a population of cells (e.g. 4, 8 or 16 cells) instead of only one cell. This is achieved by using multi hole chips. Success rates are expected to be higher as well as a larger overall current response, however, the seal resistance is expected to be lower.
(e.g. TRP channels), optogenetics
Voltage Clamp Current Clamp Dynamic Clamp
in vitro only
Our Patch Clamp Devices
The Port-a-Patch is a semi-automated device with a small footprint for the analysis of ion channels in cells and lipid bilayers.
The Patchliner is an automated patch clamp robot for medium thoughput with ultimate flexibility for assay design.
The SyncroPatch 384 is a high-throughput patch clamp instrument with a throughput of 20,000 datapoints per day. The number of parallel recordings can be reduced to 32 and multiples thereof for assay development and smaller screening projects.