Optical tweezers as tools for studying molecular interactions at surfaces : Functional Imaging and Optical Manipulation of Living Cells

It is shown here that an optical tweezer can successfully be employed to study interactions between coated microbeads and either biological surfaces, viz. membranes of neuronal cells, or artificial surfaces derivatized with amino acids. For biological applications, polystyrene beads of a diameter of 3 μm were coated with different proteins of the Extracellular Matrix (ECM) and brought into contact with glial cells and neurons. By comparing interaction forces, effects of bacterial phopholipase C, formation of membrane threads and surfing distances of bound ECM protein coated beads on cells we demonstrate a different anchorage ofthe tenascin-C receptor in primary neurons and glia. To study interactions at artificial surfaces with optical tweezers, polystyrene beads with a diameter of 10 μm were coated with different amino acids. Friction coefficients were measured between these beads and glass surfaces comprising amino acids coupled to well-defined layers of cellulose derivatives produced by the Langmuir-Blodgett technique, the technique provides an easy method for friction measurements and the characterization and quality control of surfaces. We conclude that optical tweezers are a powerful tool for the characterization of biological and artificial surfaces.