A label-free approach to identify inhibitors of alpha4beta7-mediated cell adhesion to MadCAM

Traditionally, cell adhesion assays are performed in a manual workstation format using fluorescence-based readouts. Herein, the authors describe a label-free homogeneous assay to identify inhibitors of α4β7 integrin-mediated cell adhesion to its ligand, the mucosal addressin cell adhesion molecule (MadCAM), using the SRU BIND platform. The biosensor is optically based and comprises a subwavelength polymer grating. The assay was validated using standard compounds and an α4 blocking antibody and correlated very closely with the manual assay format when running a battery of test compounds of varying potencies. Cell adhesion was strictly dependent on the presence of divalent cations where Mg(2+) was greater than Ca(2+) at promoting cell adhesion. This homogeneous and label-free format exhibited low variability with a calculated Z' of 0.6. In addition to measuring α4β7-mediated 8866 cell adhesion to MadCAM, the authors also demonstrate that this platform can measure adhesion of Jurkat cells expressing α4β1 to the vascular cell adhesion molecule. Thus, the SRU BIND platform is widely applicable to measuring cell adhesion events mediated by other integrins binding to their receptors in an assay format that is amenable to high-throughput screening.