There are three possible causes:
1. Cell density
The cell concentration of the culture may be too dense. Generally speaking, over-confluence will cause the adhesive force between cells to increase beyond the adhesive force between the cells and the extracellular matrix. This relative decrease in extracellular adhesion can lead to cells detaching from the stretch chamber.
2. Enzyme treatment
Trypsin and other enzyme treatment can damage cells. However, this may not be obvious in experiments conducted with standard dishes, because the binding to the dishes’ plastic wells is nonspecific. By contrast, when stretch chambers are employed, adhesion is attained solely by the extracellular matrix coating. Thus, relatively severe enzyme damage will cause stretch chamber adhesion to fail. Please see the tip on trypsin treatment (below) that addresses this issue.
Cells will not adhere to the stretch chamber if the coating is insufficient. This insufficiency is indicated when the chamber surface easily repels liquid after the applied coating has been absorbed. Extend the coating application and setting time should this occur.