Pharmaceutical and biotech companies face increasing demand for ion channel screening. Researchers looking to directly assess the functional interaction of chemical entities with ion channel activity have relied on the gold standard—an electrophysiological technique known as whole-cell patch clamp. This technique requires equipment from multiple vendors, a high degree of technical skill to perform and is time- and labor-intensive. To address these limitations, Molecular Devices introduced IonWorks™ HT, an automated system for high-throughput electrophysiological screening, that provides a turnkey solution with increased throughput over existing technologies. The IonWorks HT system can be used for directed primary screens, hit confirmation, safety profiling and pharmacological studies.

Download or order on CD the IonWorks HT demo video.

		Ion channel screening up to 3000 patches per day
		Complete turnkey solution
		Screen Nav, Cav, hERG and other Kv channels
		Reliable, reproducible results
		Easy to set up and run experiments
		Flexible experimental protocols

ion channel screening—up to 3000 patches per day

Ion channels have always been important pharmacological targets but have historically suffered from a number of barriers. These barriers have limited the successful introduction of clinical drugs that modulate ion channel activity, not the least of which has been the relative inability to ramp up throughput beyond conventional methods for making direct electrophysiological recordings of ion channels. The IonWorks HT system is the first commercially available screening instrument with more than two orders of increased throughput over conventional patch clamping solutions. During a screening experiment, the IonWorks HT system measures whole-cell current simultaneously, typically taking about 45 minutes to complete—translating into overall throughput of up to 3,000 patches per day, or approximately 100 eight-point IC₅₀ curves with n=4, per day. With IonWorks HT, it is now feasible to perform direct electrophysiological screens of cells expressing a recombinant voltage-gated ion channel of interest. A wide variety of cell types (e.g., CHO, CHL, HEK293, neuroblastoma) and ion channels (e.g., hERG and other K_v, Na_v, Ca_v) have been successfully employed with the IonWorks HT system.

complete turnkey system

IonWorks HT is an automated system for electrophysiological screening providing high-throughput ionic current recordings from multiple cells simultaneously. At the heart of the system is a 384-well substrate consumable—the PatchPlate™ (see Figures 1 and 2).

		Figure 1. IonWorks HT dispenses reagents and cells into the ready-to-use PatchPlate, saving time and ensuring reproducible results.

Cells expressing a voltage-gated ion channel of interest are dispensed into individual wells in parallel with an onboard fluidics system (F-Head; Figure 3) and a single cell is subsequently positioned over a single small aperture (or pore) within each well. The aperture separates two isolated fluid-filled upper and lower chambers, each containing buffered solutions and separate electrodes. Over the course of a few minutes, the positioned cells form stable seals over the apertures, impeding electrical flow between the two chambers. A cell membrane pore-forming agent (Amphotericin B) is introduced into the lower chamber, creating an electrical pathway through the portion of the cell membrane exposed through the small aperture in each of the wells.

		Figure 2. Schematic showing cross-section view of a PatchPlate well, illustrating principle technology of the IonWorks HT system.

An electronics head (E-Head; Figure 3) containing 48 electrodes is positioned into the upper chamber clamping the cell membrane potential and subsequently recording ionic currents from 48 cells in parallel. Compounds are aspirated from 96- or 384-well microplates and dispensed in parallel with a 12-channel fluidics head (F-Head) pipettor. With a completely integrated design, this turnkey system does not require highly skilled electrophysiologists for operation.

		Figure 3. View of IonWorks HT experiment deck. A 48-electrode electronics head (E) amplifier and 12-channel fluidics head pipettor (F) are indicated. From left to right, the experiment deck consists of soak station, E-Head wash station, PatchPlate, F-Head wash station, compound plate, cell boat, buffer boat, and auxiliary compound plate.

screen Na_v, Ca_v, hERG and other K_v channels

The IonWorks HT system is ideal for screening modulators of voltage-gated ion channels, such as human ether-à-go-go-related gene (hERG) and other K_v, Na_v, and Ca_v channels, and performing directed screens, hit confirmation, high throughput pharmacological and hERG safety profiling studies. HERG safety pharmacology in particular is an important application that has emerged as a result of the market withdrawal of pharmaceuticals with adverse cardiac side-effects due to hERG channel activity. The IonWorks HT system is the first commercially available system for conducting high throughput electrophysiological hERG safety pharmacology studies (Figure 4). (See also Kiss L., P.B. Bennett, et. al., High Throughput Ion-Channel Pharmacology: Planar-Array-Based Voltage Clamp Assay and Drug Development Technologies  1:127-135, 2003).

		Figure 4. High throughput patch clamp data showing 48 simultaneous current recordings from CHO cells expressing hERG channels. For more information, see the hERG channel screening assay page.

reliable, reproducible results

Whole-cell recordings from the IonWorks HT are comparable to existing patch clamp methods. The results are reliable and reproducible over time with equivalent IC₅₀ values (Figure 5).

		Figure 5. Comparison of dose response curves for 4-aminopyridine in CHO cells expressing Kv1.5 potassium channels obtained on IonWorks HT (top) and conventional patch clamp systems (bottom). For more information, see the Kv Potassium Channel Screening Assay page.

easy to set up and run experiments

The IonWorks HT system is easy to set up and operate—routine day-to-day operations can be performed by technician-level personnel. IonWorks HT allows the user to define assay protocols, control the system and analyze data through the intuitive and flexible PC graphical user interface (GUI). (See Figure 6.)

		Partial plate coverage modes to facilitate assay optimization
		All experimental settings saved in a protocol file for convenient use in future experiments
		Customize settings for Hole Test, Seal Test and Obtain Access parameters for flexibility in creating a variety of different experimental protocols

		Figure 6. Screen snapshots from IonWorks HT software showing experiment setup dialogs.

flexible experimental protocols

The GUI provides a simple interface for voltage command protocol set-up, and the ability to store and recall protocol files. In addition, it allows the user to define voltage clamp steps and ramps. Protocols are easy to setup in the Waveform Editor dialog in the IonWorks HT software (Figure 7).

		Three Reference Potentials parameters for configuring holding, conditioning and pre-signal potentials
		Up to ten Pulse Interval segments for configuring command voltage protocols
		Add Sequence Repetitions to one or more contiguous pulse intervals for protocols evaluating use-dependence

		Figure 7. Voltage command protocol for eliciting hERG currents expressed in CHO cells.

The IonWorks HT system also incorporates integrated fluidics to address compound additions. A number of standard 96- and 384-well microplates from a variety of vendors are supported. A solvent wash option is available when working with known problematic compounds (e.g., hydrophobic, viscous). (See Figure 8.)

		Supports a variety of 96- and 384-well compound plates from a number of different suppliers—non-supported plates available upon request
		Perform a solvent wash for problematic compounds
		Reduce or increase the number of wash and mix cycles to reduce the overall experiment time or for greater wash stringency, respectively

		Figure 8. Screen snapshot from IonWorks HT software showing compound and solvent wash plate setup.

Specifications*

	Dimensions (in.)	55.6 (H) x 58.1 (W) x 32.5 (D)
	Weight (lbs.)	550 (250 kg)
	Vacuum required	Minimum 120 mbar @ 0.6 m3/hr 26 in. Hg @ 0.35 cfm
	Microplate formats	Supports standard 96- and 384-well formats
	Read time	35-55 minutes/384-wells (protocol-dependent)
	Integrated 12-channel pipettor	Accuracy: >95% at 3.5 µl Precision: <10% CV at 3.5 µl
	Voltage clamp amplifier	Integrated 48-channel amplifier

*Specifications subject to change.