Fabrication and evaluation of biomimetic-synthetic nanofibrous composites for soft tissue regeneration

Electrospun scaffolds hold promise for the regeneration of dense connective tissues, given their nanoscale topographies, provision of directional cues for infiltrating cells and versatile composition. Synthetic slow-degrading scaffolds provide long-term mechanical support and nanoscale instructional cues; however, these scaffolds suffer from a poor infiltration rate. Alternatively, nanofibrous constructs formed from natural biomimetic materials (such as collagen) rapidly infiltrate but provide little mechanical support. To take advantage of the positive features of these constructs, we have developed a composite scaffold consisting in both a biomimetic fiber fraction (i.e., Type I collagen nanofibers) together with a traditional synthetic (i.e., poly-[ε-caprolactone], PCL) fiber fraction. We hypothesize that inclusion of biomimetic elements will improve initial cell adhesion and eventual scaffold infiltration, whereas the synthetic elements will provide controlled and long-term mechanical support. We have developed a method of forming and crosslinking collagen nanofibers by using the natural crosslinking agent genipin (GP). Further, we have formed composites from collagen and PCL and evaluated the long-term performance of these scaffolds when seeded with mesenchymal stem cells. Our results demonstrate that GP crosslinking is cytocompatible and generates stable nanofibrous type I collagen constructs. Composites with varying fractions of the biomimetic and synthetic fiber families are formed and retain their collagen fiber fractions during in vitro culture. However, at the maximum collagen fiber fractions (20%), cell ingress is limited compared with pure PCL scaffolds. These results provide a new foundation for the development and optimization of biomimetic/synthetic nanofibrous composites for in vivo tissue engineering.