Fabrication of hybrid tubular scaffolds using direct ink writing for tracheal regenerative application

Tracheal tissue engineering has been an alternative treatment for long-term tracheal stenosis due to the lack of donors and suitable tracheal implants. This work is meant to construct a novel hybrid tracheal support of synthetic and natural polymers using direct ink writing. A blend of polycaprolactone ( $$mathrm{PCL}$$ ) and medical-grade polyurethane ( $$mathrm{PU}$$ ) as synthetic material was used to fabricate tubular grafts. The synthetic graft was coated with various combinations of alginate ( $$A$$ ) and gelatin ( $$G$$ ) solutions using 3D printing to prepare hybrid tracheal scaffolds. The novelty in this method was the coating of the natural polymeric solution by extruding the solution over a rotating tubular graft by exploiting the advantages of 3D printing. The synthetic part has mechanical support, and the coated natural material has enhanced biological activities. Key assessments such as rheological investigations and printability studies were performed to characterize the flow behavior and fidelity of the printed constructs. Based on the above investigations, suitable combinations of alginate and gelatin ( $$A/G$$ ) were chosen and used for further investigations. The effect of natural polymer coating using 3D printing over $$mathrm{PCL}/mathrm{PU}$$ scaffold was carefully investigated using various physicochemical, morphological and mechanical investigations. Further, the hybrid tracheal scaffolds were evaluated for biological assessments such as proliferation, cytotoxicity and cell adhesion assay using human mesenchymal stem cells (hMSCs). The biological investigations showed that the coated scaffolds yielded improved biocompatibility compared to synthetic scaffolds and could be a potential tissue-engineered solution to tracheal regeneration.