Robotics, automation, and fine-tuning of microplate assays have generally smoothened the way for high-throughput screening (HTS). Now the pressure points are building in the validation and assay design areas as well as in secondary screening, squeezing the upstream and downstream process. Some clever tweaking has become necessary to reduce false hits and shrink the error bars that can expand so rapidly when screening large numbers of compounds.
Accounting for growing knowledge of genome variability, delving deeper into cell cycle and behavior, separating screening components of individual assays, and simplifying nanoliter volume assay assembly and detection are helping to overcome these obstacles. The aim overall is to increase data integrity and reduce volume and raw material usage, thus increasing the percentage of true hits.
Mike Biros, company spokesperson for SpinX Technologies (www.spinx-technologies.com), reports that his company’s nanoliter assay platform assists in “compound profiling, downstream of HTS.” SpinX’ approach offers “homogenous assays in nanoliter volumes, performing dose-response with end-point or time-course readouts.”
Generally, companies have reduced the volume of HTS assays to a sweet spot that balances cost savings with technological complexity. After HTS, however, performing assays that vary component concentrations or read at multiple time-points is still a challenge at low volumes. The SpinX technology addresses this challenge by moving and combining nanoliter-volumes of assay components on gCard™, a plastic microfluidic device, using centrifugation and a unique valve mechanism, called VLV™.
Its advantage, in comparison to available platforms, continues Biros, lies in the fact that “SpinX technology allows robust assays in 200-nanoliter volumes without characterizing the physical properties of the assay components. For instance, there is no need to define liquid classes or calibrate based on viscosity. Furthermore, classic detection modalities can be used with this technology.” In addition, “because the gCards are being spun past the detector, kinetic data is inherently collected from hundreds of assay chambers simultaneously.”
The user interacts with a gStack™, “which looks a bit like a deep-well plate. Each gStack has 12 gCards with reservoirs that can be filled with different buffers and enzymes in stock form—no dilutions are necessary. The individual cards are automatically loaded onto a rotor, where the liquids are forced through microfluidic channels into chambers. The user can specify the amount of liquid that can go into the chambers and when that liquid is moved, enabling concentration and time-dependent assays,” says Biros.
“As the rotor spins, a laser perforates a hole between two adjacent microfluidic components, either channels or chambers. Centrifugal force moves the liquid to a new chamber. It’s a very robust valve mechanism with no moving parts or external mechanical or electrical contacts.” As an example of the system’s ability, 96 10-point IC50 curves can be run after loading a single 384-well gStack in a couple of hours, Biros claims.