Abstract
We hypothesized that a composite of 3D porous melt-electrowritten poly-ɛ-caprolactone (PCL) coated throughout with a porous and slowly biodegradable fibrin/alginate (FA) matrix would accelerate bone repair due to its angiogenic potential. Scanning electron microscopy showed that the open pore structure of the FA matrix was maintained in the PCL/FA composites. Fourier transform infrared spectroscopy and differential scanning calorimetry showed complete coverage of the PCL fibres by FA, and the PCL/FA crystallinity was decreased compared with PCL. In vitro cell work with osteoprogenitor cells showed that they preferentially bound to the FA component and proliferated on all scaffolds over 28 days. A chorioallantoic membrane assay showed more blood vessel infiltration into FA and PCL/FA compared with PCL, and a significantly higher number of bifurcation points for PCL/FA compared with both FA and PCL. Implantation into a rat cranial defect model followed by microcomputed tomography, histology, and immunohistochemistry after 4- and 12-weeks post operation showed fast early bone formation at week 4, with significantly higher bone formation for FA and PCL/FA compared with PCL. However, this phenomenon was not extrapolated to week 12. Therefore, for long-term bone regeneration, tuning of FA degradation to ensure syncing with new bone formation is likely necessary.
Highlights
Results from the Chorioallantoic Membrane (CAM) assay show blood vessel infiltration into all scaffolds, macroscopically more blood vessels were seen on FA and PCL/FA scaffolds than on PCL
At the 4-week timepoint, μCT analysis of bone regeneration within the cranial defects showed increased bone volume in both the FA and PCL/FA scaffold groups compared with PCL, and the increase was significantly higher in the PCL/FA group
Islands of bone tissues were found across the defect in the PCL/FA group, while the bone regeneration happened adjacent to the host tissue, as shown in Figure 8A,C, respectively
Summary
Current surgical methods often involve grafting of either autologous, the “gold standard”, or allogenic bone, but they are subject to limitations, such as limited bone supply and donor site morbidity in the case of autologous bone graft or disease transmission, and fracture and non-union in the case of allogenic bone grafting [1] Xenogenic bone is another source of bone tissue with both osteoconductive and osteoinductive properties. Implants made of metals such as titanium and stainless steel are used to treat bone defects; they have a limited lifespan and cause stress shielding due to excessive material strength [3]. These disadvantages are driving the development of new biomaterials that can act as efficacious bone graft substitutes
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