The heliXcyto is a cell-based biosensor platform that combines optical detection with microfluidics to measure binding kinetics directly on intact living or fixed cells, under near-physiological conditions. Cells are immobilized in microfluidic traps without modification and exposed to fluorescently labelled analytes, enabling real-time acquisition of k_on, k_off, K_D, and avidity, while the native membrane environment is preserved throughout.

Single-Cell Interaction Cytometry (scIC) characterizes binding kinetics on single cells, delivering full association and dissociation curves on native cell-surface targets. It supports comparison across cell lines, primary cells, and engineered models, and is well suited for capturing avidity behavior typical of monovalent antibodies, bispecifics, and other multivalent modalities. At the single cell level, scIC resolves heterogeneity in binding strength and kinetics, making it particularly relevant for primary immune cells, patient-derived material, and cell and gene therapy applications where understanding cellular variability is scientifically important.

Challenging avidity and improving developability

Because scIC measures binding directly on native cells rather than purified targets, we use scIC at 2bind to enable functional quantification of avidity from real-time association and, in particular, dissociation behavior. Multivalent interactions manifest as slow or biphasic off-kinetics, allowing separation of true monovalent affinity from avidity-driven stabilization. By maintaining target mobility and density in the cell membrane, scIC reveals candidates whose apparent potency is highly dependent on clustering or overexpression, rather than intrinsic affinity. This mechanistic insight supports more informed ranking of binders and selection of molecules with predictable in vivo performance and improved developability.

Enabling hard-to-purify targets
Many high-value membrane proteins, such as GPCRs, transporters, and ion channels, are notoriously unstable or conformationally sensitive when isolated. Our 2bind scIC workflow bypasses purification entirely, providing kinetic data on receptors presented in their native lipid environment and correct folding state. This greatly reduces artefacts introduced by detergent solubilization or reconstitution and allows kinetic analysis for targets that were previously inaccessible to label-free or surface-based systems. Consequently, scIC extends real-time kinetic characterization to a wider range of biologically and therapeutically important targets, bridging the gap between early discovery and cellular relevance. Single cell interaction cytometry thus offers a complementary, cell-contextualized view of molecular interactions, supporting better-informed decisions in antibody and drug discovery, target validation, and translational research.