Rheological studies of diatom encapsulation in silica gel

The mutual influence of the mineral and biological components of a specific bio-hybrid system consisting of diatom cells entrapped in a silica gel was studied by rheological methods. Small amplitude shear stress oscillatory measurements indicate that the culture medium alone has a strong impact on the silica network formation and viscoelastic properties. In contrast, the presence of diatoms does not significantly perturb the sol–gel process, and leads to a moderate change in the gel elasticity. Compression tests show that a large difference exists between the mechanical properties of silica gels and diatom shells, suggesting a limited impact of the gel strength on the diatom survival rate. We also show that the biological activity of entrapped diatoms can modify the structural evolution of the silica gel. This work indicates that rheological methods may be important tools for the optimization of whole cells encapsulation procedures and further confirms that encapsulated diatoms are able to interact with the surrounding silica materials.