This study investigated the in vitro degradation characteristics of macroporous
hydrogels based on
poly(propylene fumarate-co-ethylene glycol) (
P(PF-co-EG)). Four formulations were fabricated to test the effect of porosity and cross-linking density on the degradation of the resulting macroporous
hydrogels. Macroporosity was introduced by the addition of
sodium bicarbonate and
ascorbic acid, the precursors of the
carbon dioxide porogen, in the initiation system for the
hydrogel cross-linking. Macroporous
hydrogels with porosities of 0.80 +/- 0.03 and 0.89 +/- 0.03 were synthesized by the addition of
sodium bicarbonate of concentrations 40 and 80 mg/mL and
ascorbic acid of concentrations 0.05 and 0.1 mol/L, respectively.
Poly(ethylene glycol) diacrylate (
PEG-DA) was utilized as a cross-linker. The molecular weight between cross-links had a significant effect on
weight loss after 12 weeks, where samples with M(C) of 1,880 +/- 320 synthesized with a
P(PF-co-EG):
PEG-DA ratio of 3:1 had a significantly greater mass loss due to degradation than those with M(C) of 1,000 +/- 100 synthesized with a
P(PF-co-EG):
PEG-DA ratio of 1:1. In contrast, porosity played a minimal role in determining the
weight loss. Mechanical testing of the
hydrogels under confined compression showed a decrease in compressive modulus over the degradation time for all formulations. In addition, an increase in
hydrogel equilibrium water content and pore wall thickness was observed with degradation time, whereas the
hydrogel porosity and surface area density remained invariant. The results from microcomputed tomography corroborated with the rest of the measurements and indicated a bulk degradation mechanism of the macroporous
hydrogels.