Advanced Insights into Receptor Expression and Avidity Binding Dynamics on Cells Using IndEx-2 and heliXcyto in Drug Development

Watch our latest SelectScience webinar on single-cell Interaction Cytometry (scIC)! Our Director of Biophysics Dr Nichole Cerutti is joined by Dr Vivien Hafner from Bruker Biosensors to explore the power of scIC and its use in drug development. Key points include:

• scIC and how it can be used to characterise the kinetics of therapeutic molecules 
• our brand-new Bruker biosensor – the heliX^cyto
• using our trademark IndEx-2 platform to measure target expression

What is scIC? 

Single-cell Interaction Cytometry (scIC) is a transformative technology that enables the detailed study of individual cell interactions within complex biological systems. It’s facilitated by the heliX^cyto biosensor, an innovative next-generation, chip-based technology from Bruker Biosensors. This examines the biophysics of drug binding kinetics at the single-cell level – providing real-time data on how therapeutic molecules interact with cell targets in their native cell environment. 

Performing scIC with heliX^cyto can capture association rates (ka), dissociation rates (kd), affinity constants (KD). ScIC has unique benefits over other techniques such as Surface Plasmon Resonance (SPR) and flow cytometry (FACs), including: 

• Native cellular context: scIC measures binding on the cell surface, preserving the target’s natural structure, density, and interactions. 
• Complete kinetic analysis on live cells: unlike endpoint assays like FACs or ELISA, scIC can capture real-time binding and unbinding events. This measures binding stability and residence times essential for therapeutic dosing. 
• Exceptional sensitivity: this enables detection of low-abundance targets and is compatible with a range of analytes from small molecules to nanoparticles, peptides, and even viruses. 
• Dual-colour and FRET capabilities: scIC’s dual-colour fluorescence and FRET detection capture real-time fluorescence signals, providing valuable data on fast binding events, particularly for small molecules and specific receptor interactions.
• Comprehensive cell target analysis: traditional biosensors like SPR and BLI are limited by shallow detection depths and less effective cell immobilisation, restricting cell-based measurements. With its 30 μm detection depth, scIC captures binding events across the cell surface for a fuller analysis.
• Multiphasic binding analysis: scIC uses biphasic fit models to distinguish complex, multiphasic interactions, making it invaluable for studies on biologics and antibodies, where multivalent binding often occurs.

Read more about how scIC compares to SPR techniques. 

Our brand-new biosensor 

The heliXcyto uses flow-permeable cell traps, immobilising cells in an automated workflow. This allows for real-time measurement of interactions on cells, yielding biophysical data in the characterisation of difficult to produce membrane targets. Applications include kinetics, affinity, and avidity.

Our dual-inducible IndEx-2 system enables fine control of titratable protein expression levels. Combining this with technologies like the heliX^cyto can deepen our understanding of therapeutic interactions at the cellular level. Notably, RoukenBio is the only drug discovery service provider with IndEx-2 technology. 

Implications for drug discovery 

ScIC is a powerful tool for analysing binding interactions across biologics, small molecules, and cellular therapies. Understanding how therapeutics bind to their biological targets is essential to drug development. This has applications across oncology, immuno-oncology, autoimmune diseases, allergy, and inflammatory conditions.