FIGURE 1.

Synthesis of a vmIPN and characterization. (A) Schematic of sequential polymerizations and grafting chemistry used to synthesize the vmIPN. Drawing not to scale. Molecular weights of the CH₂CH₂O repeat for m and n are 1000 and 3400, respectively. (B) Swelling behavior of first poly(acrylamide) (pAAm) layer in water. Swelling ratio (S.R.) is calculated as in Table 1. After swelling in water, surface features appeared in the first vmIPN pAAm layer of low moduli (e.g., <1000 Pa for 10 wt% gels) which have high swelling ratios. The pAAm layers shown at S.R.∼1.8 were 13.5 ± 1 Pa. After 10 min in a 50/50 v/v water:isopropyl alcohol (IPA) solution, surface morphology was altered in the first vmIPN pAAm layer of low moduli (e.g, <1000 Pa for 10 weight % gels) which have high swelling ratios. After the second polymerization of the vmIPN, surface features persisted in 50:50 v/v isopropyl alcohol (IPA)/water solvent conditions, but were absent in 3:97 v/v IPA/water solvent conditions. (C) The aNSC response was specific to peptide ligand on vmIPNs. The aNSCs adhere and proliferate on bsp-RGD(15) peptide-modified vmIPNs, whereas they form nonadherent cell aggregates on bsp-RGE(15) peptide-modified vmIPNs. Both substrates have an elastic modulus of 97.8 ± 8 Pa (Table 1). These phase-contrast images were taken after 3 days of culture in FGF-2 proliferating media conditions.