Molecular adhesion assay for biopolymer systems.

Molecular adhesion plays a central role in many biological systems, yet existing methods to quantify adhesive strength often struggle to bridge the gap between single-molecule resolution and biologically relevant environments. Here, we present a scalable micromagnetic bead-based adhesion assay capable of quantifying detachment forces under physiologically meaningful conditions. Designed to probe mucoadhesion in the context of mucociliary clearance, our system applies controlled magnetic forces to ligand-coated beads adhered to functionalized substrates and tracks detachment events using high-speed microscopy and calibrated z-displacement mapping. The platform combines control of substrate and bead surface chemistry with high-throughput imaging and in situ force calibration via Stokes drag. We demonstrate the ability to distinguish sub-nanonewton to nanonewton force regimes across a range of bead-substrate pairings, including carboxyl-carboxyl, polyethylene glycol-polyethylene glycol, and cell culture-derived human bronchial epithelial mucus interactions. Surface functionalization was validated via fluorescence imaging and zeta potential measurements, while detachment forces were used to estimate binding energy and infer dissociation constants. This assay enables detailed characterization of multivalent, force-sensitive adhesive interactions and offers a powerful new approach to studying bioadhesive systems, including mucus-pathogen interactions and drug delivery materials.