The invention relates to porous a hydrogel matrix having substantially interconnected tunnel-shaped micropores with a three-dimensional configuration of an interconnected hollow tetrapod network. Such matrices may be used to entrap motile cells that migrate into the micropores of said matrix. The matrices of the invention are formed by a method comprising the steps of providing a solution of a hydrogel-forming material, providing a template material with a three-dimensional configuration corresponding to the negative configuration of the desired interconnected porous structure of the hydrogel material, said template material comprising interconnected zinc oxide tetrapod (t-ZnO) networks, casting the solution of hydrogel-forming material onto the template and removing the template material from the hydrogel material by acid hydrolysis of the template material.