App Note: Accurate measurement of free analyte using Gyrolab^® platform vs ELISA

The importance of measuring free analyte in complex matrices during preclinical and clinical studies is undisputed. However, quantification using immunoassays presents inherent technical challenges that can result in overestimations. Incubation steps that can disrupt the equilibrium of free and bound analyte are the main source of error and can vary with the assay technology used.

In this study, the free concentrations of biotherapeutics Avastin® (bevacizumab) and Lucentis® (ranibizumab) were measured using Gyrolab immunoassays where samples have very short contact time with capture reagent and ELISA with extended incubation time for analyte binding.

Overestimations were observed for Avastin using ELISA, where the complex t½ is about the same as the incubation time in the assay, but not for Gyrolab® platform, where the capture reagent exposure time is very short.