Scheme 1. Graphical Representation of the Fabrication of Hollow Collagen Microspheres and Protein Loading/Release.

The process involves the sulfonation of a commercially available polystyrene bead of defined size, coating of these beads in a collagen solution, cross-linking of the coating, and removal of the polystyrene bead core. Spheres are incubated with loading buffer overnight to allow NGF loading into the spheres. Collagen microspheres, a protective reservoir of growth factor, are applied to neuronal cells and promote their survival and growth by sustained delivery of neurotrophins.