The environment of cells is a key parameter that influences their behaviour. Therefore, offering a synthetic 3D environment to the cells enables us to control and investigate cellular 3D behaviour in vitro. Our 3D environment is a hydrogel with interconnected hollow microchannels. These microchannels originate from a sacrificial template of interconnected ZnO-tetrapods. They form an interconnected network and are embedded in a hydrogel. By dissolving the template by an acid treatment after polymerization, hollow channel structures appear within the hydrogel. 
The hydrogel can be adjusted in stiffness and biofunctionalization. These properties of the 3D environment can be adapted during the preparation of the hydrogel. Different mechanical properties of the hydrogels can be achieved by varying the crosslinker concentration. Furthermore, a well-defined chosen biofunctionalization can be applied. Both properties can be modified according to the cell type and the specific aims of a study. One intention is to investigate cellular behaviour towards different stiffnesses of the hydrogel after the preparation of the 3D environment.
We show that cells, such as Acanthamoebae castellanii  and fibrosarcoma cells, can migrate into the 3D hydrogel microchannels, which enclose the cells almost completely and mimic the dense environment of the extracellular matrix. They stay viable for several days after first incubation. Therefore, our microchannel-containing material can be used to control cell behaviour in an adjusted 3D environment by varying the mechanical properties and biofunctionalization of the hydrogel. It has the potential to be used in implants, where soft and porous 3D environments are desirable. 
 Y. K. Mishra et al., Materials Today 21, 2018, 631-651.
 S. B. Gutekunst et al., ACS Applied Biomaterials 2018 (Under Revision).