Simultaneous Measurement of Cardiac hERG and Nav1.5 Currents Using an Automated Qube Patch Clamp Platform
With the ever-increasing emphasis on ion channel profiling in safety screening, there has been a drive towards increased throughput with respect to patch clamp profiling. The advent of automated 384 well plate-based planar patch clamp instruments such as the Qube has significantly aided in this effort, allowing for a significant increase in the number of compounds that can be profiled in a time and cost-effective manner.
To further explore the possibility of increasing efficiencies in these systems, we examined whether it would be possible to measure multiple currents from separate cell lines in a single well of a 384-well plate using the Qube instrument.
Theoretically, the instrument lends itself to this possibility due to the virtue of being able to select plates that contain multiple holes per well. Hence by adding two independent cell lines, each independently stably expressing a recombinant ion channel, it should be possible to patch two or more cell lines per well.
We have compared a variety of conditions in the study in order to generate a robust assay that allows for the simultaneous profiling of both the NaV1.5 peak and hERG currents. NaV1.5 and hERG currents were separated temporally by virtue of the design of the voltage protocol. Our results show that the success rates of simultaneously recording both NaV1.5 and hERG currents in each well were 34.4%, 87.5%, 93.8%, 93.8% and 93.8% in 2, 6, 10, 16 and 36 hole/well QChips, respectively. The potencies of 28 CiPA compounds on NaV1.5
peak and hERG currents were determined individually in a single cell line format or in a mixed cell format using a 10-hole/well QChip. The correlation of the IC50 for the compounds was excellent for both hERG (R2=0.96) and NaV1.5 (R2=0.86) when comparing the single-cell line format with the mixed cell format.
Our data demonstrate that it is possible to generate a robust and reproducible assay using a single voltage protocol and buffer combination that allows for the measurement of the effects of compounds on both hERG and NaV1.5 currents simultaneously. Such a format can both significantly increase assay throughput and reduce assay costs while maintaining data quality.