Fig. 2. SEM photomicrographs cross-section of a gelatin nano-non-woven. Magnification 300x (left) and 1000x (right)
On the other hand, polymeric nano-non-wovens obtained by electrospinning are characterized with strictly controlled morphology of pores, which depends on the material or the solvent used for the spinning and other parameters of the process (Fig. 2). From a large selection of available materials, one could choose materials that can be then easily removed from the obtained scaffolds. Such nano-non-wovens were regarded as non-classic pore precursors that enable for obtaining the structures of desired morphology (defined by nano-non-woven). Their additional advantage, in comparison to conventional precursors, is the formation of pores in the entire volume of the scaffold. It guarantees the formation of pores that are evenly distributed, not only inside the scaffold but also on one of the surfaces.
In the next stage of the study, poly-L-lactide scaffolds have been prepared using a gelatin nano-non-woven as a non-classic pore precursor. Also, a combination of a gelatin nano-non-woven and classic pore precursors was used (PVP or PVP and Pluronic®). Analogical tests were conducted for other polyesters (PCLA and PCL).
A small number of pores having a diameter of about 5 µm was observed on the bottom surface of the scaffold obtained from poly-L-lactide using a gelatin nano-non-woven (Fig. 3). On the other hand, numerous irregular pores of the size of 20–50 µm could be seen on the upper surface. Here, ”imprints” of nanofiber were also observed, application, pressing and washing out of which have destroyed the thin covering layer. In the cross-section of the scaffold, there were irregular and mutually linked pores 20–80 µm in size. Their 2–5 µm thick walls contained oval pores of a size of 1–2 µm. Also, walls of the pores, similarly to those at the upper surface, contained ”imprints” of nanofiber which proves the efficiency of using the non-wovens. In the scaffolds obtained with the nano-non-wovens, the ”imprints” of gelatin nanofibers were observed.