Designing microporous macromolecular hydrogels for biomedical applications: a comparison between two techniques

A comparison between two different techniques, namely gel leaching technique (GLT) and a phase inversion technique (PIT),to induce a connected micro-porosity in polymer hydrogels is presented. The gel leaching technique (GLT), applied to an acrylamide hydrogel, consists of carrying the crosslinking reaction within the interstitial space of an agarose gel which, after the setting of the acrylamide hydrogel, is removed by increasing the temperature above its melting point. Following this procedure, an ordered interconnected porous structure is scripted within the acrylamide hydrogel. The phase inversion technique (PIT), applied to a cellulose hydrogel, consists of a quick desiccation of the swollen hydrogel by phase inversion. This is obtained by increasing the swollen sample in a bath of acetone that has a low affinity for the hydrogel but a very high affinity for water. In this case, due to the rapid water removal, a connected but non homogeneous microporosity is achieved. Swelling studies performed on samples obtained by both techniques demonstrated an enhancement of the equilibrium water sorption properties induced by the presence of porosity. However, by comparing the sorption data, the GLT led to a higher enhancement in sorption properties compared to the PIT indicating that beside the degree of porosity also the degree of interconnectivity and the pattern of porosity may control the sorption properties of polymer hydrogels.