Figure 2

Morphology and properties of the different CGS regions. SEM images of regions A, B and C post-fabrication demonstrating the biomimetic structures to the corresponding native tissues as well as high porosities. (A,E) The overall morphology of the electrospun nanofibers for both regions A and B (scale bar 100 µm). (B,F) Higher magnification images showing the morphology of individual nanofibers and the pore spaces between them. Smooth nanofiber surface can be observed and a biomimetic fibrous structure similar to skin and soft tissues (scale bar 5 µm). (C,G) TEM images of PLGA-Gelatin Coaxial nanofibers with a clear core–shell structure, where gelatin is contained in the core and covered with a PLGA shell. (D,H) The size distribution of electrospun nanofibers in both regions A and B ranged between (400–1100 nm), mimicking the size range of collagen fibril found in the native skin and soft tissues. Both regions A and B exhibited high porosity with average pore volumes of 97.68 ± 0.65% and 97.96 ± 0.98%, respectively. The overall morphology of the sintered microspheres in region C (I) before and (J) after the incorporation of gelatin-mTG hydrogel into the pore spaces of the construct (scale bar 500 µm). (K) Higher magnification image showing the interconnectivity between microspheres and gelatin-mTG hydrogel occupying the pore spaces (scale bar 100 µm). (L) PLGA microspheres size distribution in region C ranged between (300 µm – 600 µm), resulting in an optimal pore volume for bone tissue regeneration (41.64 ± 1.65%). Red dotted lines represent the nanofiber shell (PLGA), white dotted lines represent the core–shell (gelatin) of the nanofiber, and white arrows represent gelatin-mTG hydrogel.