Compositional control of poly(ethylene glycol) hydrogel modulus independent of mesh size

Poly(ethylene glycol) (PEG) hydrogels are of great interest in tissue engineering because of their established biocompatibility, high permeability, and tunable material properties. However, rational design of PEG hydrogel scaffold properties has been inhibited by the interdependence of key material properties such as modulus and mesh size. This study examined the effect of an acrylated 4-arm PEG cross-linker on gel modulus and mesh size as a means of inducing local increases in cross-link density to decouple these two parameters. It was determined that adding the 4-arm PEG cross-linker to PEG hydrogels resulted in statistically significant increases in both tensile and compressive modulus while having minimal effects on overall gel mesh size. The incorporation of the 4-arm PEG cross-linker also broadened the range of achievable mechanical properties. This study provides the methodology to independently tune PEG hydrogel modulus and mesh size, which may be utilized in future investigations of the individual and combined effects of PEG hydrogel modulus and mesh size on cell behavior and viability. It also presents a more finely tunable hydrogel scaffold with utility in a broad range of tissue engineering applications.