The Competition RED Device was developed in association with pharmaceutical laboratories to more accurately model in vivo drug interactions by enabling equilibrium dialysis experiments to be performed in a multiplexed format involving competition for binding among different tissues. The RED Device is an apparatus for performing equilibrium dialysis experiments in a high-throughput, automation-compatible format, and consists of disposable inserts and a base plate formatted to a standard microplate footprint.

The Competition RED Device system consists of disposable dialysis tube inserts and a reusable base plate made of high-grade PTFE. The base plate is much like our regular RED Device plate except that it is divided into different size chambers (wells) for positioning 2–8 RED Device inserts per well. The format enables competitive dialysis experiments involving 2–15 separate tissue or protein fluid samples.

Each Competition RED insert contains either one or two separate dialysis chambers (each package includes a selection of both types). The Competition RED Device requires no extensive assembly or specialized equipment, and each chamber/well is easily accessible from the top of the device. The Competition RED Device extends the power of equilibrium dialysis by facilitating analysis of simultaneous drug interactions and partitioning among multiple tissues.

Features of the Competition Rapid Equilibrium Dialysis (RED) Device:
• Easy to use—disposable tubes require no presoaking step, assembly, or specialized equipment
• Short incubation time—design provides high surface-to-volume ratio of membrane to sample, enabling equilibrium to be reached within 2–4 hours
• Flexible format—base plate contains several different chamber sizes, enabling small molecule partitioning studies involving 2–16 tissue or protein samples without waste
• Robust—compartmentalized design eliminates potential for cross talk or leakage
• Reproducible and accurate—perform controlled experiments with multiple tissues to obtain screening results that have high predictability for in vivo studies with animal models
• Validated quality—base plate is composed of chemically inert high-grade PTFE, eliminating non-specific binding and risk of contamination; each lot is functionally tested in a protein binding assay for guaranteed performance

Applications:
• ADME-Tox studies: in vitro screening of drug partitioning between plasma and multiple tissues before in vivo studies with animal models
• Aids in determining formulation of drug dosage for in vivo studies
• Drug-drug interaction studies
• Competitive binding and dissociation constant determination for small molecules versus multiple targets

Determining the extent to which a molecule partitions between plasma and specific tissues in the body is a critical phase of drug development because it determines compound dosing, efficacy, clearance rate, and the potential for drug interactions or tissue damage. Although final assessment of these variables invariably requires animal dosing and analysis, in vitro screening systems that are rapid and have good predictability are highly desirable for ADME-Tox studies.

Equilibrium dialysis is among the most successful in vitro screening method for evaluating drug binding and dosage requirements. Equilibrium dialysis is used to estimate the non-bound drug fraction in plasma or drug partitioning between red blood cell and plasma, plasma and liver microsomes, or plasma and tissue homogenates. However, many tissue-partitioning studies indicate that certain drugs show significant binding to tissues tested individually but have considerably different binding preferences when placed in competition between multiple tissues.

Features of the RED Device inserts:
Each single-use, disposable insert is made of two side-by-side chambers separated by a vertical cylinder of dialysis membrane (in 8K or 12K MWCO) validated for minimal nonspecific binding. This format requires no extensive assembly steps or specialized equipment, and each chamber or well is easily accessible from the top of the insert after insertion in the base plate. Additionally, the high surface-to-volume ratio of the membrane compartment allows rapid dialysis, where equilibrium can be reached in four hours with high levels of reproducibility and accuracy. In many cases, experiments can be completed in less than 100 minutes.

• Disposable—require no presoaking, assembly, or specialized equipment
• Short incubation time—large dialysis surface area accelerates equilibrium
• 8K MWCO membrane—ideal molecular-weight cutoff for protein-drug binding studies
• 12K MWCO membrane also available for larger drug molecules
• Membrane composition—regenerated cellulose with low glycerol content as a humectant

Features of the RED Device base plates:
RED Device inserts are designed to be used with either the reusable PTFE or disposable high-density polypropylene base plates. Each RED Device base plate holds up to 48 RED Device inserts and has a standard 96-well plate footprint with 9 x 9 mm well spacing to provide compatibility with automated liquid handling systems. In addition, the disposable RED Device base plates are available pre-loaded, providing operation convenience for scientists conducting protein-binding applications. No pre-conditioning of the membrane inserts is needed. When using radioactive materials, this single-use plate is easily disposed of to avoid contamination and cleaning.