FIG. 3.

Characterization of fibrin/PEG hydrogels. (A) Fibrin hydrogels became opaque upon gelation, while fibrin/PEG hydrogels remained translucent. (B) Gelation time of low-concentration fibrinogen (5 mg/mL) solutions at 37°C was on the order of seconds, while gelation of PEGylated fibrinogen (0.5 mg/mL PEG) was significantly slower. A similar effect was seen in higher concentration fibrinogen (10 mg/mL) and PEGylated fibrinogen gels (1.0 mg/mL PEG). (C) After 14 days in vitro, high-concentration fibrin-only scaffolds in media alone were completely degraded, while fibrin/PEG hydrogels remained intact. (D) The shear storage modulus (G′) of samples ranged from 50–150 Pa. Fibrin/PEG hydrogels were not significantly softer compared to fibrin-only hydrogels at either given concentration, although the higher concentration fibrin gels were significantly stiffer than the low-concentration fibrin/PEG gel. (E) Scanning electron microscope images revealed that fibrin-only hydrogels contained very thin fibrils, while fibrin/PEG hydrogels contained much larger bundled structures. Scale bars are 10 μm. (F) Pores throughout fibrin hydrogels were not uniform, as seen by significant differences in the major and minor pore axes. Overall pore sizes were significantly smaller in fibrin/PEG samples. (G, H) No significant difference was seen in AFSC attachment or viability after 7 days when comparing fibrin-only, fibrin/PEG, or Matrigel. A value of p<0.05 (*) was considered significant in all tests. PEG, poly(ethylene glycol). Color images available online at www.liebertpub.com/tea