Credit: © 2009 Wiley

The ability of a cell to reversibly stick to another material is important in many areas of biology and tissue engineering. One such area is the control of cell migration, which is itself controlled by choreographed cell adhesion and detachment steps. Now, Huawu Shao from the Chengdu Institute of Biology, Xingyu Jiang from the National Centre for Nanoscience and Technology in Beijing, and co-workers, have used the light-sensitive isomerization of azobenzene to create1 a surface with reversible cell-adhesion properties.

The scientists covered a gold surface with a self-assembled monolayer (SAM) comprising two types of thioloated alkanethiols. The major SAM component was terminated by a hexa(ethylene glycol) unit — which resists non-specific cell-adhesion — and the secondary component had an azobenzene moiety bonded to a terminating peptide that is capable of specific cell-adhesion.

Azobenzene exists in two isomeric configurations that interconvert on the absorption of specific wavelengths of light. In one configuration the cell-adhering peptide is 'buried' in the surrounding hexa(ethylene glycol) units and in the other it is sticking out above them. Light could therefore be used to reversibly switch the peptide's position and control the surface-adhesion properties. Fibroblast cells were shown to stick to the SAM, detach when irradiated with light with a specific wavelength and then reattach on irradiation of light with another wavelength.