Single ligand and receptor binding spectroscopy using an atomic force microscopy

Binding and unbinding between individual ligands and receptors were measured and quantified using an atomic force microscopy (AFM). Initially, the cell stiffness is characterized by force-distance measurements using ligand-free AFM tips and compared to several cancer and non-cancerous cells. Then, we measured the unbinding force with peptide-coated AFM tips, targeting specific cell receptors. The unbinding force between the ligand and receptor was measured to be an order of 100 pN. Such individual, specific interaction measurements were further supported by pre-blocking the cell receptors with the excess, free ligands.