In summary, we have developed a novel type of AFM adhesion
assay allowing the measurement of specific interactions between
ligands at a polymeric hydrogel probe and cell receptors. With this
approach we aimed at mimicking cell adhesion events in the
physiological situation were soft and hydrated materials are
involved. Conducting such experiments with hard, inorganic AFM
probes would pose pitfalls as they are prone to non-specific interactions
and interfere with the functionality of coupled ligands.
Here, the fabrication of functionalized PEG microparticles as AFM
probes was based on a straightforward route and yielded a dense
layer of HA ligands. By comparing the adhesion to CD44 presenting
and non-presenting cells we could show that HA-SCPs specifically
bind to CD44 receptors. Furthermore, the AFM experiments
showed that CD44 and HA binding is significantly faster than
adhesion and spreading of the cells on surfaces. This indicates, that
CD44 and HA mediate cell adhesion in the early stages.