3D-printing of solvent exchange deposition modeling (SEDM) for a bilayered flexible skin substitute of poly (lactide-co-glycolide) with bioorthogonally engineered EGF

Biodegradable polyesters have been widely used as rigid biomedical apparatus because of high mechanical properties but few flexible implants. Herein, we report a flexible poly(lactide- co -glycolide) (PLGA) scaffold using a rapid in situ formation system based on phase separation by solvent exchange deposition modeling (SEDM), which was different from traditional 3D printing of fused deposition modeling (FDM). The FDM printed product was rigidity, its Young's modulus was approximate 2.6 times higher than that of SEDM printed sample. In addition, the thickness of the solidified ink would not shrink during the SEDM printing process, its surface had nano-/micro pores in favor of protein immobilization and cell adhesion. Then a flexible bilayered scaffold with nano-/microstructure was constructed combing SEDM with electrospinning technology for skin substitute, wherein the SEDM printed sample acted as a sub-layer for cell and tissue ingrowth, the densely packed electrospun nanofibers served as an upper-layer improving the sub-layer's tensile strength by 57.07% and preventing from bacteria as physical barrier. Ultimately, the bilayered scaffold immobilized epidermal growth factor (EGF) by a bioorthogonal approach was successfully applied to facilitate full-thickness wound healing of rats.