Preparation of resorbable collagen-based beads for direct use in tissue engineering and cell therapy applications

For tissue engineering and cell therapy applications, expansion of cells such as chondrocytes on beads in spinner culture can provide advantages compared with monolayer culture. The use of resorbable beads that can be included as an integral part of the construct provides the advantage of minimizing the extent of cell handling and eliminating a final trypsin treatment to detach cells from the bead. In this study, we have made various types of beads based on native collagen and denatured collagen (gelatin). The beads have been stabilized by different extents of glutaraldehyde cross-linking, and characterized by a combination of chemical analysis, thermal stability, and microscopy. In vitro examination in the presence and absence of chondrocytes showed that stability increased with the extent of crosslinking and could also be influenced by the manner of fabrication. On the basis of the in vitro stability studies, gelatin beads of a defined stability were shown to resorb over time in subcutaneous implants in nude mice compared with more stable demineralized bone particle (DMB) carriers. These data indicate that for direct use in tissue engineering or cell therapy applications, where resorbable beads can be used for cell expansion and then direct delivery of cells, it is possible to design suitable carrier beads with a range of stabilities that match the implant requirements.