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AUTOMATED SCREENING

 

Very often, the screening in preliminary assays demands data generation with high throughput, low cost and great quality. The throughput of the manual patch clamp is limited to 30 data points per day and the high-cost approach is a limiting factor.

The advent of the automated patch clamp offers considerable advantages in ion channel screening throughput since it is a cost-effective method to screen and profile promising leads and to assess potential liabilities earlier in the drug discovery and development process.

hERG safety

The DI.V.A.L. TOSCANA hERG Safety service is a cell-based assay which employs the IonFlux™ 16 System (Molecular Devices) as an automated patch clamp electrophysiology measurement.

The IonFlux™ 16 System is a compact automated patch clamp system based on a unique microfluidic design that combines compounds, cells and buffers on a single plate with standard 96 well plate format. Wells are connected by microfluidic channels, and solutions are moved by pneumatic pumps, eliminating automated pipetting and allowing for immediate replacement of compounds with buffer solution. A heater provides temperature control with a precision of 0.1°C and can heat the microfluidic channels from room to physiological temperature in times comparable to manual patch clamp (̴̴ 1 min).

The IonFlux™ 16 is ideally suited for ion channel research and assay development.

The system utilizes 20-cell ensembles for each amplifier channel to improve data consistency and success rates. 

- The human ether-a-go-go related gene (hERG) encodes the inward rectifying voltage gated potassium channel in the heart (IKr) which is involved in cardiac repolarisation.

- Inhibition of the hERG current causes QT interval prolongation resulting in potentially fatal ventricular tachyarrhythmia called Torsade de Pointes.

- The IonFlux™ 16 System offers unmatched flexibility, fluidic sophistication and affordability for ion channel research. Integrating microfluidic perfusion with standard well plates produces an  automated electrophysiology system that looks and operates with the simplicity of a benchtop microplate reader. 

hERG safety protocol

Instrument

IonFlux™ 16 System (Molecular Devices)

Analysis Method

Electrophysiology

Cell Line

HEK-293 cells

Test Article Concentration

0.008, 0.04, 0.2, 1, 5, 25 μM (different concentrations available)

Final DMSO Concentration

0.25%

Number of Replicates

4 replicates per concentration

Quality Controls

0.25% DMSO (negative control)

Dofetilide (positive control)

Seal resistance must be > 50 MOhms

Pre-compound current must be ≥ 0.1 nA)

Test Article Requirements

100 µL of 10 mM solution

Data Delivery

IC50 determination

 

High throughput screening

Using the IonFlux™ 16 System is possible to perform several applications on sodium (Na+) and potassium (K+) voltage-dependent channels transfected in HEK-293 (human embryonic kidney) or CHO (Chinese hamster ovary) cells. These applications are:

• Compound efficacy screening

• Compound profiling in the low nanomolar and high micromolar range (IC50 determination)

• Mutant screening

• Mechanism of action studies

For recording Na+ currents (hNav 1.7 and hNav 1.8 and their mutants), cell arrays will be voltage clamped at a holding potential of -80 mV, stepped to -120 mV for 50 ms to maximize channel availability, and then to -10 mV to open the Na+ channels (50 ms). The final step will be to -50 mV (or -70 mV), followed by ten to twelve 10 mV increments.

For recording K+ currents (for example hERG currents), cell ensembles will be voltage clamped at a holding potential of -80 mV and activated at +50 mV (800 ms). The outward tail current at -50 mV will be measured by subtracting a baseline reading at -50 mV before activation from the peak outward tail current at -50 mV after activation. A step to -120 mV (800 ms) after the -50 mV repolarization step will be also included for recovery of hERG channels from inactivation. The voltage protocol is applied every 6 s.