Crosslinking characteristics of and cell adhesion to an injectable poly(propylene fumarate-co-ethylene glycol) hydrogel using a water-soluble crosslinking system

The crosslinking characteristics of an injectable poly(propylene fumarate-co-ethylene glycol) [P(PF-co-EG)]-based hydrogel were investigated. A water-soluble crosslinking system was used, consisting of poly(ethylene glycol) diacrylate (PEG-DA), ammonium persulfate (APS), and ascorbic acid (AA). The effects of PEG block length of the P(PF-co-EG), APS concentration, AA concentration, and PEG-DA concentration on equilibrium water content, sol fraction, onset of gelation, mechanical properties, and endothelial cell adhesion were studied. The equilibrium water content of the hydrogels ranged from 57.1 +/- 0.3 to 79.7 +/- 0.2% whereas the sol fraction ranged from 2.5 +/- 0.0 to 3.33 +/- 5.4%. The onset of gelation times varied from 1.1 +/- 0.1 to 4.3 +/- 0.2 min. For all hydrogel formulations, the tensile strength fell between 61.7 +/- 18.2 and 401.3 +/- 67.5 kPa and tensile moduli ranged from 0.4 +/- 0.0 to 3.3 +/- 0.3 MPa. Endothelial cells attached to the hydrogels in a range of 3.9 +/- 1.4 to 31.1 +/- 14.1% of cells seeded. These findings suggest that injectable poly(propylene fumarate-co-ethylene glycol) hydrogel formulations in conjunction with a novel water-soluble crosslinking system may be useful for in situ crosslinkable tissue-engineering applications.