Generation of porous poly(ethylene glycol) hydrogels by salt leaching

Poly(ethylene glycol) (PEG) hydrogels have been investigated for a number of applications in tissue engineering. The hydrogels can be designed to mimic tissues that have desired chemical and mechanical properties, but their physical structure can hinder cell migration, tissue invasion, and molecular transport. Synthesis of porous PEG hydrogels could improve transport, enhance cell behavior, and increase the surface area available for cell adhesion. Salt leaching methods have been used extensively to generate porous biomaterial scaffolds but have not previously been applied to hydrogels. In this article we describe a modification of traditional salt leaching techniques for application to hydrogels. Salt-saturated polymer precursor solutions are prepared, and salt crystals of a defined size are added before polymerization. The salt crystals are then leached out, resulting in porous hydrogels. Examples are provided for application of this technique to PEG hydrogels. Porous PEG hydrogels were generated with pore sizes ranging from 15 to 86 microm and porosities from 30% to 75%. Porous hydrogels that were incorporated with a cell adhesion peptide supported cell adhesion with morphology varying with pore size. The simple, reproducible technique described here could be used to generate porous hydrogels with controlled pore sizes for applications in tissue engineering.