Ford et al. 10.1073/pnas.0506020102. |
Fig. 6. (a) Mechanical properties of the isotropic PEG-polylysine hydrogel. The elastic or storage modulus (G') is constant throughout the frequency studied, which is expected for a fully gelled system. The elastic modulus is used to determine the crosslinking density and effective molecular mass between crosslinks. The loss or storage modulus (G'') decreases as expected at higher frequencies. (b) Enzymatic degradation of the isotropic PEG-polylysine hydrogel. When incubated in a 0.01 mg/ml of trypsin solution, the hydrogel fully degrades within 24 hours. The gel initially gains volume, as noted by the negative value for degradation. This negative value is likely due to bonds being broken in the gel, which increases the ability of the gel to further hydrate permitting an increase in swelling.
Fig. 7. Twenty-micrometer cryotomed cross sections of hydrogels seeded with GFP expressing NPCs after 7 days in culture. There is a down-regulation of nestin (red) (a), an immature neural maker, and an up-regulation in glial acid fibrillary protein (GFAP) (red) (b) and neurofilament (red) (c) in the presence of the serum-containing BEC media. Nuclei are stained blue with DAPI.
Movie 1. In vivo observation of fluorescently labeled blood flow on implanted hydrogels by using FITC-dextran (molecular mass: 70 kDa). Video includes three postimplantation time points: 2, 4, and 6 weeks. At each time point, the blood flow appeared identical among the different groups; therefore, the representative videos were chosen on the basis of the clarity of the footage. Week 2: Chromatic view of coculture (neural progenitor cells, NPCs; brain endothelial cells, BECs) hydrogel. Week 4: Monochromatic view of NPC gel. Week 6: Monochromatic view of NPC:BEC gel. Flow is visualized by the movement of nonfluorescent red blood cells. Worth noting is the week 2 hydrogel. In phase, a large red vessel is observed. Under fluorescent excitation, this same vessel becomes opaque and fluorescent vessels are observed underneath (see explanation in the article). Also of importance are the layers of vascular networks observed at all time points.