Fabrication of crosslinked carboxymethylchitosan microspheres and their incorporation into composite scaffolds for enhanced bone regeneration.

Carboxymethylchitosan (CMCS) microspheres were prepared by the carboxymethylation of chitosan (CS) beads using monochloroacetic acid. The CMCS microspheres were crosslinked using two different methods: the amine-amine crosslinker genipin and carbodiimide chemistry, yielding Gen-X CMCS and X-CMCS beads, respectively. The Gen-X CMCS beads were found to have poor degradation and drug release profiles. The X-CMCS microspheres displayed good potential for use in tissue engineering applications in which degradation and local drug delivery are desired. The X-CMCS beads displayed enzymatic degradation of 82.7 ± 1.2% in 100 μg/mL lysozyme after 1 month. An extended release of rhBMP-2 for at least 45 days was also observed with the X-CMCS microspheres. Scaffolds were formed by fusing beads together, and the X-CMCS beads were successfully incorporated into composite X-CMCS/CS scaffolds. The composite scaffolds had increased degradation of 14.5 ± 6.6% compared to 0.5 ± 0.4% for CS-only scaffolds, and the X-CMCS/CS scaffolds released more rhBMP-2 at all timepoints. The composite scaffolds also supported the attachment and proliferation of SAOS-2 cells. The addition of X-CMCS beads resulted in fabrication of scaffolds with improved properties for use in bone tissue engineering.