KCAS has more than 20 years of experience providing protein binding support for clinical and pre-clinical investigations. Three separate approaches can be used for these investigations – ultrafiltration, ultracentrifugation and equilibrium dialysis. Each approach has its own advantages and preferences within the industry.


The main advantage of ultrafiltration is rapid sample processing, which typically takes 40 minutes or less, making it an ideal process for unstable compounds. Another advantage is that the devices used are disposable and relatively inexpensive. However, some compounds may bind to the various components of the devices, which could potentially invalidate its use.


An advantage of ultracentrifugation is that it’s a single-component system. Samples are simply placed in thick walled tubes (i.e., polycarbonate) and centrifuged at very high g-forces. Draw backs of this technique include the limited number of samples that can be processed at a given time, moderately long times for processing (typically four hours) and the disruption of lipoproteins.


A classic technique used for the assessment of protein binding is using a closed system with PTFE donor/receiver cells. A key advantage of this technique is minimal non-specific binding and historic reference. Disadvantages include long processing times (four to 24+ hrs), bacterial growth concerns with prolonged dialysis times and leakage/volume shifts.

KCAS can validate the appropriate protein binding platform for your drug using either cold or radiolabeled analysis.

Assay parameter validation includes:

  • Non-Specific Binding
  • Concentration Dependency
  • pH Dependency
  • Binding to Selective Plasma Proteins
  • Freeze/Thaw and Long-Term Stability