Photocrosslinkable dextran hydrogel films as substrates for osteoblast and endothelial cell growth

Functional hydrogel films on solid supports are versatile materials with large potential for cell growth and tissue engineering. Here, we report on a modular approach to generate functional hydrogel composite films for endothelial and osteoblast cell co-culture. The polymer network of the parent hydrogel was formed by a dextran derivative (BP-CMD), which contained carboxymethyl (CM) groups for further chemical functionalization and benzophenone (BP) moieties as a photocrosslinkable unit. BP-CMD could be synthesized by three different routes, first with the benzophenone unit attached via an amide bond, or second by an ether bond, or third as an ion pair between the benzophenone ammonium salt and the carboxylate groups on the dextran backbone. For composite formation, BP-functionalized silica nanoparticles, as well as gelatin particles were mixed with BP-CMD and permanently fixed in the hydrogel matrix by photocrosslinking for mechanical reinforcement and to facilitate cell growth. In the last preparation step the BMP-2 growth factor was covalently coupled to the polymer backbone, which enhanced osteoblast and endothelial cell growth. The swelling behavior and successful BMP-2 immobilization of the hydrogel composite films were investigated with surface plasmon resonance and optical waveguide mode spectroscopy coupled with fluorescence detection. This modular approach allows independent selection and optimization of each component in the hydrogel composite for a wide range of potential applications for targeted cell growth, as successfully shown here with osteoblast-endothelial cell co-culture for bone tissue regeneration.